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DOE/SC-0034

Tropospheric

Aerosol

ProgramRG99 060050.3

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Program Plan

March 2001

U. S. Department of EnergyOffice of ScienceOffice of Biological and Environmental ResearchEnvironmental Sciences Division



DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any employees, nor any of their contractors, subcontractors or their employees, makes

any warranty, express or implied, or assumes any legal liability or responsibility for theaccuracy, completeness, or any third party’s use or the results of such use of anyinformation, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by theUnited States Government or any agency thereof or its contractors or subcontractors.The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Available electronically at-

http://www.doe.gov/bridge

Available to U.S. Department of Energy and its contractors in paper from-

U.S. Department of EnergyOffice of Scientific and Technical InformationP.O. Box 62Oak Ridge, TN 37831(423) 576-8401

Available to the public from-

U.S. Department of CommerceNational Technical Information Service5285 Port Royal RoadSpringfield, VA 22131(703) 487-4650

Printed on recycled paper



iii

ForewordThe Department of Energy (DOE) and itspredecessor agencies, the Atomic Energy

Commission and the Energy Research andDevelopment Administration, have a long andenviable record of accomplishment in thescience of atmospheric aerosols. Thisresearch, which had its genesis in the study offall-out from atmospheric weapons testing, hasfound valuable new application in under-standing the environmental effects of fossilfuel combustion and allied energy-relatedactivities.

Now, consistent with the Nation's desire topreserve and enhance our environment andminimize the risk to human health and welfare

from atmospheric pollutants, the atmosphericscience research community faces a newchallenge to develop sensible and effectivestrategies to achieve the new NationalAmbient Air Quality Standard for fine particles,the so-called PM-2.5 standard. Achieving thisstandard in a way that will have minimumimpact on the Nation's ability to meet itsenergy requirements requires a much morecomplete understanding of the processesgoverning the loading, composition, andmicrophysical properties of these aerosolsthan is now available.

Fine particles are implicated in anotherimportant issue that may affect the Nation'senergy economy, namely climate change.Fine particles scatter solar radiation,decreasing the amount of the sun's energythat is absorbed by the planet and therebyexerting a cooling influence on climate. Themagnitude of this influence is not known forcertain, but recent estimates indicate that it iscomparable to the warming influence ofincreased concentrations of greenhouse gasesand may consequently be offsetting a majorfraction of the greenhouse warming that wouldotherwise have been experienced over theindustrial period. Because aerosols are short-lived in the atmosphere this effect cannot be

considered a mechanism for forestalling thegreenhouse effect. But to understand climatechange it is necessary to obtain accurateestimates of the totality of climate influencesover the industrial period, and in particular theaerosol influences.

The Tropospheric Aerosol Program (TAP)described in this Program Plan will makecrucially-needed contributions to improvedunderstanding and model-based description ofthe loading and properties of atmosphericaerosols in relation to sources, pertinent toboth of these major environmental issues.Scientists from the DOE National Laboratorycommunity together with colleagues from theacademic community, the private sector, andother governmental agencies responsible forunderstanding and maintaining ouratmospheric environment have contributedsubstantially to the preparation of this Plan.

The talent required to understand and resolvethese important national issues lies collectivelywithin and beyond the Department of Energy.Thus we view TAP as a component of alarger, informal national aerosol program,where TAP both contributes to and leverages

other aerosol research efforts. Indeed, TAP isdesigned to fill some very important gaps andcomplements existing programs. We lookforward to working closely with our partnerswithin DOE and in other state and federalagencies, industry, and academia.

With this cooperative effort TAP will serve theobjectives of these communities and therebymake a major contribution to meeting thegoals of the Air Quality Research Sub-committee of the Committee on Environmentand Natural Resources, while at the same time

supporting the DOE mission of fostering aNational Energy Strategy that takes intoaccount the preservation and enhancement ofthe Nation's atmospheric environment.

Dr. Ari PatrinosAssociate Director for Biological and

Environmental ResearchOffice of ScienceU. S. Department of Energy



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v

Executive SummaryAir quality in the United States has improved

substantially over the past three decades as aresult of the Clean Air Act and itsamendments. However, a few majorunresolved issues remain in accomplishingthe task of minimizing the public’s risk to airpollution exposure. Key among these is therelation of adverse health effects to exposureto airborne particles, or “aerosols”.

The significance of the environmental stress ofparticulate air pollution and the mechanisms ofits action on humans remain unresolveddespite years of research. Historically,attention has shifted from crude measures ofexposure represented by the massconcentration of “total suspended particles” tomore refined measures that segregate massconcentration by the upper limit particle size,initially 10 µm and more recently 2.5 µm.However it is not established that it is themass concentration of particulate matter that isin fact responsible for its health effects. Asknowledge has evolved and measurementmethods have improved, health scientistshave begun to turn their attention to the

chemical components present in particles.This has led to the recognition that availablemeans of determining chemical properties maybe limiting the identification of components inparticles responsible for their influence onhuman health.

In addition to their influence on health, fineparticles affect public welfare in otherimportant ways. These particles scatter andabsorb light, leading to impairment of visibilityand to a potential influence on climate changethat must be quantified to understand the full

implications of increasing concentrations ofgreenhouse gases. Light scattering andabsorption by fine particles also affect surfaceirradiance, with a potential resultant influenceon plant growth and length of the growingseason. Deposition of fine particles and theirprecursors to the surface affects the chemicalbalance of ecosystems, not just by so-called"acid deposition" but also by alteration ofnutrient balance. For these reasons also

quantitative understanding is required of the

processes that control the atmosphericloading, composition, and microphysicalproperties of fine particles, together with thecapability to represent these processes inatmospheric chemical transport models.

In 1997, the U.S. government made acommitment to reduce fine particles in the airby modifying the National Ambient Air QualityStandards (NAAQS) by establishing a newstandard for fine particulate matter, the PM2.5standard. The public debates that took placein developing this standard revealed thatscientific information supporting this nationalobjective continues to have unacceptably highlevels of uncertainty. As a result, the nationhas embarked on a substantial new programof research to reduce these uncertainties.Initial attention has focused mainly on two ofthe technical issues necessary to reduce thisuncertainty: characterizing human healtheffects due to exposure to fine particles anddetermining the nature and extent of fineparticle exposure across the United States, asspecified by the new NAAQS.

While the above two elements are key todefining the root cause of the health effectsand to identifying the geographic locations ofnon-attainment, they will fall short of leading toan efficient approach to controlling theproblem. To achieve this goal the newnational program needs two more elements: agreatly improved system for quantitativelycharacterizing emissions, and greatlyimproved understanding of the basic physico-chemical processes responsible for theformation of particles and evolution of their

properties in the atmosphere. Without theseelements it will not be possible to link emissionreductions with reductions in particleconcentrations and thereby formulate arational and efficient strategy to achieve thePM2.5 standard. Absence of this knowledgealso precludes developing strategies thatwould be targeted to specific substances infine particulate matter that might achieve realbenefits to human health.



ContentsForeword ...................................................................................................................................iii

Executive Summary ................................................................................................................. v

1. Introduction ..............................................................................................................................1

1.1 Tropospheric Aerosols and Their Importance ...................................................................1

1.2 Priority Components of TAP .............................................................................................3

1.3 Benefits to be Derived from TAP........................................................................................5

1.4 Consequences of Not Doing this Research ....................................................................... 5

2. Overview and Background ......................................................................................................7

2.1 The TAP Initiative...............................................................................................................7

2.2 Fine Atmospheric Particles ................................................................................................7

2.3 The DOE Context............................................................................................................. 12

2.4 The Science Context for TAP........................................................................................... 13

2.5 The TAP Approach .......................................................................................................... 15

3. The TAP Objectives ................................................................................................................ 173.1 What TAP will Accomplish ............................................................................................... 17

3.2 TAP Research Tasks and Scientific Issues ..................................................................... 17

4. Organizational Structure .......................................................................................................19

4.1 Organizational Elements of TAP ...................................................................................... 19

4.2 Science Team .................................................................................................................. 20

4.3 Science Support Team .................................................................................................... 20

4.4 Integration ........................................................................................................................ 20

4.5 Oversight and Interagency Coordination ......................................................................... 21

4.6 Relation to Other DOE Programs.....................................................................................21

4.7 Relation to Other Federal Programs................................................................................ 23

5. Science Implementation ........................................................................................................ 25

5.1 Field Measurements ........................................................................................................255.2 Instrument Development and Advanced Characterization............................................... 35

5.3 Modeling .......................................................................................................................... 41

5.4 Laboratory Studies and Theory........................................................................................ 45

6. Science Support Implementation ......................................................................................... 51

6.1 Support for Field Studies ................................................................................................. 51

6.2 Data System and Archive ................................................................................................ 55

6.3 Support for Modeling Activities ........................................................................................ 56

6.4 Scientific Communication................................................................................................. 57

7. Deployment Schedule and Resource Requirements ..........................................................59

7.1 TAP Science Team .......................................................................................................... 60

7.2 TAP Science Support Team ............................................................................................ 61

7.3 TAP Project Support ........................................................................................................617.4 Capital Items .................................................................................................................... 61

References ..............................................................................................................................67

Appendices ............................................................................................................................. 67

Appendix A Workshop Participants ......................................................................................... 73

Appendix B Instrumentation and Characterization Techniques Available for Use in TAP........ 77

Appendix C Relationship Between TAP and Other Federally Funded PM Research Programs.... 85

Appendix D Acronyms.............................................................................................................. 89



1

1. Introduction

1.1 TroposphericAerosols andTheir ImportanceThere is a compelling body of evidencethat increasing concentrations oftropospheric aerosols from humanactivities are potentially major factors in

human health and welfare.

Tropospheric aerosols are suspensions of fineparticles, of diameter ranging fromnanometers to micrometers, in the lower fewkilometers of the atmosphere. Thesesuspensions derive from “primary” sourcesinvolving direct emissions of particles, and by“secondary” processes, reactions of gaseousprecursor emissions in the atmosphere to formparticulate matter.

Fine airborne particles have been associated

with adverse influence on human health innumerous studies. Much of the relevantresearch is summarized in the 1999 Draft EPACriteria Document for Particulate Matter (EPA,1999a), which identifies the following effects:(1) lung function decrements; (2) respiratorysymptoms, or exacerbation of symptomsrequiring bronchodilator therapy; (3) hospitaladmissions for respiratory and cardiovascularcauses; (4) emergency medical visits; and (5)death largely from cardiopulmonary causes inthe elderly. {pp 8-33 - 8-34]. The documentpresents a detailed examination of healtheffects associated with ambient particulatematter, examining the results of severalstudies that attempted to quantitativelydetermine the relative risk associated with agiven concentration of PM. That examinationconcluded that "All of these long-term studiesreport many statistically significant findingsassociated with long-term mean PMconcentrations. " [page 8-32]. However there

remain important unresolved questions aboutthe mechanism of insult, and whether theinsult depends solely on the massconcentration of particles or on their chemicalconstituents.

Aerosol particles are also responsible forvisibility impairment not just in urban areasand multi-city complexes, but also overwidespread areas that encompass NationalParks and wilderness areas for which it isdesired to protect and enhance air qualityrelated values. Aerosol particles and theirprecursors are the carriers of a number ofhazardous air pollutants, and are the chemicalagents responsible for acid deposition. Theyare also recognized to exert a major influenceon the shortwave radiation energy budget ofthe Earth, and in the aggregate anthropogenicaerosols may be offsetting a major butunknown fraction of the anthropogenicgreenhouse effect.Of these several issues, the issue of aerosolinfluences on human health is viewed ashaving the highest priority in setting research

directions and priorities.

Evidence suggesting adverse consequencesfor human health of airborne particles has ledto the establishment of a series of NationalAmbient Air Quality Standards (NAAQS)designed to reduce the risks of breathingpolluted air. The most recent NAAQSestablished in 1997 has objectives for cleanair based on fine particle mass concentration.The controversy surrounding the scientificbasis for this standard has resulted inCongressional direction to re-examine and

elaborate on this scientific information.Atmospheric processes are central to this re-examination because of their critical role indetermining aerosol properties governing theirhealth effects.

In response to this direction, agencies of thegovernment have initiated a national programto investigate the origins, evolution and healthconsequences of fine particles and their

Fine airborne

particles are

associated

with

respiratory disease,

visibility

reduction,

acid

deposition,

and climate

change. Of

these issues,

the issue of

aerosol

influences on

human health

assumes the

highest

priority for

setting

research directions.



TAP Program Plan

2

chemical constituents. Much of the impetusfor the direction of fine particle research lieswith the Committee on Research Priorities forAirborne Particulate Matter of the NationalResearch Council (NRC, 1998; 1999; 2001).

This enterprise is coordinated by the FederalInteragency Air Quali ty ResearchSubcommittee (AQRS), and much of theresearch is implemented in collaboration withNARSTO (formerly North American ResearchStrategy for Tropospheric Ozone, but nowsimply NARSTO, in recognition of itsexpanded effort directed to particulate matter;see NARSTO, 1999). NARSTO is apublic/private partnership, whose membershipspans government, the utilities, industry, andacademe throughout Mexico, the UnitedStates, and Canada. Its primary mission is tocoordinate and enhance policy-relevantscientific research and assessment oftropospheric pollution behavior, with thecentral programmatic goal of determiningworkable, efficient, and effective strategies forlocal and regional air-pollution management.

The evolving US national program focusing onthe risks and management of the healtheffects of fine particles has four majorcomponents:

• Health Science. Establishment of asystematic approach to substantiallyadvance knowledge about the mechanismsand specific insults leading to healthconsequences of exposure to fine particlesin ambient air. The health science

component recently has been established through the efforts of the

Environmental Protection Agency (EPA) following the recommendations of the

NRC Committee.

• Monitoring Networks. Establishment of ahierarchy of measurement sites nationwidefor monitoring the mass concentration,chemical composition and size distributionof fine particles. A national network of measurements and air monitoring has

been designed and is being implemented through the EPA, the

Department of Agriculture, the Department of Interior, and state

environmental authorities.

• Emissions. Establishment of a program todetermine the emissions of fine particlesand their gaseous precursors that willpermit the preparation of much moreeffective management strategies. The

investigations leading to improvement in knowledge of emissions involve work

of EPA, the Department of Energy (DOE), state and local air quality

management agencies, and the private sector, including the electric utilities (e.g., EPRI, the Electric Power Research

Institute), the fossil fuels industry (e.g.,American Petroleum Institute) and the

t ransportat ion industry (e.g. ,Coordinating Research Council).

• Atmospheric Processes. Improvingknowledge about the atmosphericprocesses that govern the characteristicsand evolution of airborne particles so thatmethods for quantitatively linking emissionwith exposure can be made available formanagement purposes. The investigation of tropospheric aerosol processes currently is supported by a number of

sponsors in the public and private sectors, including DOE, the National

A t m o s p h e r i c a n d O c e a n i c Administration (NOAA) and the National

Science Foundation (NSF).

These four components of the nationalprogram are coordinated through the AQRSand NARSTO. A compilation of particulatematter research activities in the United Statesis maintained by the Health Effects Institute(HEI, 2001).

Critical Mass. Much progress has beenmade recently in initiating programs to meetthe national needs through the first twocomponents, health science and monitoringnetworks. Progress has also been made in

the emissions arena, however accurateemission inventories remain a large area ofuncertainty in linking what is present in the airto what is emitted by natural andanthropogenic sources. Similarly, while muchpioneering research in atmospheric processeshas been accomplished by NOAA and otheragencies, including DOE, these efforts havenot yet reached critical mass.



Introduction

3

There are substantial and critical gaps inknowledge and understanding of theatmospheric processes associated withaerosols, and so the Tropospheric AerosolProgram (TAP) is being developed tocomplement on-going efforts at NOAA andother agencies, to help fill those gaps.

The research program presented here, theTropospheric Aerosol Program (TAP), will bea sustained and cohesive means ofinvestigating atmospheric processes affectingairborne particles, focusing on theatmospheric transformation processes thatgovern the mass concentration, chemicalcomposition, and microphysical properties offine atmospheric particles.

TAP will therefore specifically address thefourth research component of the nationalprogram, improving knowledge of atmosphericprocesses governing loading and properties offine atmospheric particles. TAP will takeadvantage of new measurement technologiesfor gases and particles that have emerged inrecent years and will enhance the state of theart of measurement and characterization offine particles. TAP will thus contributesubstantially to the measurement data base ofloadings and properties of fine particles,thereby considerably augmenting the second

component of the national fine particleresearch effort noted above.

Because the atmospheric loading of fineparticles derives in great measure from energyproduction and use, and because of DOE'sstatutory responsibility to conduct researchinto the environmental consequences ofenergy-related activities, DOE is prepared toorganize and act as the principal agent forTAP.

This Program Plan presents an overview ofthe research to be conducted in TAP. Thisplan is a natural outgrowth of reviews,assessments, and workshops undertaken overthe past few years by the NRC (NRC, 1998,1999, 2001), the AQRS (AQRS, 1998, 1999),NARSTO (NARSTO, 1998a, b, c; Hales, 1998;Hidy et al., 1998), and by several of the DOElaboratories (PNNL, 1999).

TAP will

focus on the

atmospheric

transformation

processes

governing

aerosol

loading,

composition,

and

properties .

This plan was prepared at the initiative of theDOE Office of Biological and EnvironmentalResearch (OBER) (within the DOE Office ofScience) in response to these crucial nationaland energy-related needs. These effortswere also encouraged by and coordinatedwith colleagues in the DOE Office of EnergyEfficiency and the DOE Office of FossilEnergy.

After a draft version of this document hadbeen circulated, a workshop was held atBrookhaven National Laboratory in June,1999, to gain input from a broad communityrepresenting scientists from DOE NationalLaboratories, other Federal laboratories,academia, and the private sector, and officialsin the various Federal agencies responsiblefor air quality and aerosol research. A list ofparticipants is given in Appendix A.

Following the Workshop a PreliminaryProgram Plan was prepared incorporatinginput from workshop participants and others towhom the draft had been made available.That document was circulated to Workshopparticipants and to other scientists andofficials in the several cognizant Federalagencies and was made available on theWorld Wide Web. This Program Plan is arefinement of that document that takes intoaccount comments and suggestions on the

Preliminary Program Plan.

1.2 PriorityComponents ofTAPThe principal objective of TAP is to determinethe role of atmospheric processes ingoverning the physical and chemical

characteristics of aerosols that are responsiblefor human health effects. These processesare the link between the emissions that areresponsible for atmospheric aerosols andaffected individuals who breathe them.Mathematical models of these processes arethe primary tools scientists use to organizescientific knowledge into a comprehensiveunderstanding of these links betweenemissions and exposure.



TAP Program Plan

4

Highest

priority components

of TAP

research are

chemical

composition

of fine

particles as a

function of size,

chemical

dynamics and

co-pollutant

interactions,

and

estimating

the response

of fine particle

properties to

changes in

particle and

gaseous

precursor

emissions.

Table 1.1. Illustration of Institutional Priorities for Strategic ElementsAddressing the Health Effects Associated with Airborne fine Particles

Critical element ofscientific knowledge

Key toHealth

Concern

Uncertainty inLevel ofCurrent

Knowledge

Link withAtmosphericProcesses

Currentcontributionby Others

ProposedTAP

Contribution

Number/surface/ mass-particle size

distribution

H* L (H fornanoparticles)

M L H

Chemical composition-size distribution

H* M-H H M H

Particle morphology(incl. internal-externalmixtures)

H* H* L-M L-M M-H

Chemical dynamicsand co-pollutantinteraction

M-H* H H M H

Optical properties L M M M M

Physical and

meteorologicalprocesses

M-H* H H M H

Response of particleloading to change inemissions

H H H M H

Symbols H, M, and L denote high, medium, and low, respectively.

*Health research is expected to refine and improve requirements for knowledge in these areas before the

final design of TAP.

They are also the tools that regulators mustuse in determining how changes in emissionsmight affect human exposure to atmosphericaerosols and, consequently, their humanhealth effects. Construction of models thatrelate emissions of air pollutants to ambient airconcentrations and to their physical andchemical characteristics will, therefore, be aprimary focus of TAP research.

Experience has shown that development andtesting of these models is best achieved byconducting a series of field experiments,guided and supported by theoretical andlaboratory studies, that focus on the keyprocesses that govern aerosol formation,transformation, transport, and removalintegrated by analysis and interpretationleading to preparation and evaluation of themodels.

Table 1 lists critical elements of scientificknowledge that are needed to understand thelinks between emissions and exposure. Alsoincluded is an assessment, based on currentknowledge, of the relative importance of theseelements to human health concerns.

Recently representatives of different agenciesof the Federal government and industry werepolled to estimate the priorities (high, mediumand low) that each of the components listed inTable 1 would have for advancing knowledgerelevant to managing health risk fromexposure to fine particles. The results areincluded in the table to illustrate the prioritysetting the TAP community proposes to refinein developing its design.

The results strongly suggest that the highest

priority components for initial TAP planning



Introduction

5

include the chemical composition of fineparticles as a function of their size, thechemical dynamics and co-pollutantinteractions of fine particles, the physical andmeteorological influences on fine particleconcentrations, and the means to estimate theresponse of fine particle properties withchanges in particle and gaseous precursoremissions.

In keeping with the present outlook of theAQRS, advancing the knowledge of regionalhaze and the component of aerosol forcing ofclimate change are designated second andthird priorities for TAP. Because the origins ofregional haze are closely linked with fineparticle concentrations at the surface andaloft, new knowledge of the sourcescontributing to haze will emerge naturally from

TAP experiments.

The field experiments envisioned in the TAPdesign will incorporate a major airbornesampling component. Thus important “targetsof opportunity” will present themselves toconduct cooperative projects with atmosphericradiation research projects to determine thefine particle optical effects that bear onvisibility and radiative transfer over urban andrural areas of the U.S.

1.3 Benefits to beDerived from TAPThe US has relied on a number of strategiesto reduce particulate air pollution over the pasttwenty nine years. As air quality hascontinued to improve, decision makers haverecognized that the management of majorpollutants requires consideration of theconsequences to one component withchanges in another. The recognition of

interactions between pollutants creates theneed for highly complex conceptual models tominimize the risks of overly simplisticdecisions for emissions reductions.

Although significant progress has been madein improving the nation’s air quality,substantial costs have been incurred. Thepotential additional costs per increment ofimprovement in air quality are expected to rise

significantly in meeting up-dated NAAQS.Therefore, it is critical to acquire newknowledge about the fine particles and theirlinkages to other air pollutants to insure thatcontinued investment in air qualityimprovement will achieve the goal of greatlyenhanced public health and welfare at minimalcost.

The research to be conducted by TAP,described in this Program Plan, togetherwith that of other agencies, will providemajor advances in knowledge about theprocesses that govern evolution of fineparticles in the troposphere.

This knowledge will be used as a primarymeans to advance the development of greatly

improved predictive capability for aerosolparticle loading, properties, and geographicaldistribution that is required for informeddecision making.

Decision making needs to rely increasingly onthe ability to examine the consequences ofalternative strategies to achieve a given airquality objective, which may take a forminvolving either mass concentration orchemical composition, or both. The principalmeans of achieving this objective lies in theapplication of reliable air quality models.

With the national program addressing inparallel the four major elements of the fineparticle problem, and with TAP serving as afocal point for atmospheric processes, this willprovide in the next decade a timely andcomplete portfolio for creating greatlyimproved air quality models relating sourcesand human exposure to fine particles, andco-pollutants. This knowledge will aidsignificantly in creating methods for selectionof optimum strategies to reduce the healthrisks of exposure to fine particle incombination with gaseous components,including ozone, sulfur dioxide, and thenitrogen oxides.

The secondary benefits of TAP will includenew knowledge about the optical properties offine particles, as well as their evolutionaryprocesses which, in turn, will fill gaps inimportant knowledge needed for considering



TAP Program Plan

6

reductions in regional haze, and for particleinfluences on climate alteration.

1.4 Consequences

of Not Doing thisResearchThe nation has committed major resources toresolve the human health consequences ofexposure to fine particles in the atmosphere.This problem is an exceedingly complex onethat has eluded effective solutions despite along history of research and air qualitymanagement practice over the past thirty

years.

The necessary resources have beencommitted through recent Congressional andadministration actions to attack the healthconsequences of fine particle exposure.However, a comparable commitment for theparallel development of the necessary,advanced tools to inform decision makersabout ambient air management is not yetavailable.

The capabilities of the scientific community

are commensurate with the formidable task ofobtaining this kind of information, but need tobe focused in cohesively through acooperative and collaborative initiative such asTAP, in the framework of the nationalprogram.

The timing of investigations leading to majorimprovements in mathematical models forquantifying emissions to ambient airconcentration (and human exposure) is criticalto insure that timely strategies can bedeveloped as early as possible to minimizethe risk of delaying pollution managementdecisions, or taking a less than optimaldirection in management approaches.

If the national fine particle program engages inresearch on only two of the four majorstrategic elements, the necessary advancedinformation for decision making will bedelayed far into the future. TAP offers theopportunity, at a level of $20-40 million a year,to focus the necessary scientific resources toaddress the fourth component of the national

research program on fine particles.

At this critical level of commitment, initiatingTAP at this time will insure that its productswill be available for strategy development inthe period 2005-2011. This is the period whenthe NAAQS for fine particles will be reviewedagain in its five year cycle, and when critical,major decisions will be made forimplementation of national efforts to reduceairborne particle exposures simultaneouslywith resolving parallel problems associatedwith tropospheric ozone, and regional haze.

Without the benefit of results from TAPthere is a significant risk of choosing anon-optimum and hence less efficient ormore costly pathway to a combinedsolution for these problems.



7

TAP is a

highly focused

observational

and analytica

research

effort that will

compare

observations

and model calculations

to improve

capability of

modeling

aerosol

loadings and

properties

within known

and reasonable

accuracy.

2. Overview andBackground

2.1 Development of

TAPThe Tropospheric Aerosol Program (TAP) is aprogram being developed by the Office ofBiological and Environmental Research(OBER) of the Department of Energy directed

to gaining improved scientific understandingand model-based representation of theprocesses controlling the mass loading,geographical distr ibut ion, chemicalcomposition, microphysical, and opticalproperties of tropospheric aerosols. Thisprogram is a continuation of DOE's effort todevelop understanding and predictivecapability for the atmospheric influence ofenergy-related activities and their effect onhuman health and welfare. The TAP programis a highly focused observational andanalytical research effort that will compare

observations and model calculations toimprove this modeling capability within knownand reasonable accuracy.

This Preliminary Program Plan specifies theobjectives of TAP and presents the need forthis understanding and capability to representthese processes in atmospheric models. ThePlan then presents the approach that will betaken by TAP to conduct the researchnecessary to develop this understanding andmodel-based representation.

2.2 Fine Atmospheric

Particles

Aerosol particles in the atmosphere resulteither from introduction of particles into theatmosphere (primary aerosols) or from

conversion of gaseous substances in theatmosphere to particulate matter (secondaryaerosols). Aerosols result from naturalprocesses and from human activities.Examples of natural aerosols are sea saltresulting from breaking waves, windblownmineral dust, smoke from wildfires, and thenatural haze that is recognized in place namessuch as the Blue Ridge Mountains. Aerosolsfrom human activities include smoke anddiesel exhaust as well as visibility reducing"industrial haze" or "smog." In cities andnearby regions anthropogenic aerosols (thatis, aerosols resulting from human activities)dominate aerosol loading.

Motivated by the desire to protect humanhealth, the U.S. has recently adopted a newNational Ambient Air Quality Standard(NAAQS) which for the first time sets a limit onthe mass loading of particulate matter ofaerodynamic diameter of less than 2.5 µm

(termed the PM-2.5 or fine particle standard).The restriction of this standard to fine particlestakes into account the understanding that fineparticles are capable of penetrating well intothe lungs with the resultant possibility of healthimpairment. Two standards have beenissued: annual average concentration, 15 µg

New Ambient

Air Quality Standards for

the first time

limit mass

loadings of

fine particles.

m-3, and 24-hour average, 65 µg m-3. Theneed to achieve the national standards isbased on an increasing body of evidence thatindicates that fine particulate matter in theatmosphere is responsible for adverse humanhealth effects. The increased focus on the fine

particles comes as a result of advancingknowledge of the apparent risk of inhalingpollutant aerosols with the potential forexacerbating respiratory ailments and otherdiseases.

The PM-2.5 standard, as is the case forambient air quality standards generally,imposes a requirement on states and other

jur isdict ions to achieve a specif ied mass



TAP Program Plan

8

Figure 2.1. Annual average mass-loading and composition of sub 2.5-µm aerosol based on at least one year

of monitoring at two or more sites in the same region. Data were obtained using a variety of non-federal

reference methods and should not be used to determine compliance with the PM-2.5 NAAQS. From EPA

(1998).

loading of aerosols in ambient air but does notspecify a means of achieving this standard.Devising such a strategy requires at minimuman understanding of the source-receptorrelation that is responsible for the aerosolloading at a given location. This in turnrequires answering such questions as therelative contribution to aerosol loading ofprimary and secondary aerosols, and therelative contributions of natural andanthropogenic aerosols. Figure 2.1 shows

large differences in the composition of sub 2.5µm aerosol as a function of geographicallocation. It is necessary as well to understandthe geographical dependence of aerosolproperties and loading, as governed by ratesof formation and removal, dilution, andtransport in the atmosphere.

Present information on aerosol loadings in theUnited States indicates that exceedances of

Because of

differences in

aerosol

properties in

different regions there

can be no

universally

effective

means of

achieving the

PM2.5

standard.the PM-2.5 standard will be widespread,although the extent of such exceedances isnot known in detail because there is not yet awidespread database of measurementsperformed according the EPA referencemethod for fine particles. The EPA hasembarked on a major measurement programof fine particle mass loading in order todevelop such a data base (EPA, 1999b). It isclear however that simply establishing theextent of exceedances is only a first step to

developing a compliance plan. Achievingcompliance with the new PM-2.5 standards willrequire understanding of the processesresponsible for fine particle loading at a givenlocation, the sources responsible for emissionsof fine particles and their gaseous precursorsand their rates and geographical distribution,the atmospheric transformation processesresponsible for modifying the amount andnature of aerosol material, and the transport



Overview and Background

9

TAP will

focus on the

life cycle of

atmospheric

aerosols.

and dispersion processes that govern localconcentrations, in brief the processesresponsible for aerosol loading at a givenlocation. Figure 2.1 makes it clear that therewill be no single answer to these questionsthat is applicable to the entire country.Likewise it is reasonably anticipated that theanswers to these questions will depend alsoon season as a consequence of seasonaldependence of the mix of anthropogenic andnatural emissions and also seasonaldifferences in controlling meteorology andatmospheric chemistry.

Understanding the processes that control theloading, distribution, and properties ofsubmicrometer aerosols is going to be difficult.Aerosols are chemically and physically much

more complex than gaseous pollutants, andthe overall process governing aerosolloadings, properties, and distributions is muchmore complex than for primary pollutants suchas SO2 and CO. Aerosols are veryheterogeneous in composition and sources,ranging from seasalt, dust and tire particles, tosulfates, nitrate, organics and soot, as well asmixtures of these materials. Some of theaerosols are emitted directly as particles,whereas others form in the atmosphere fromgaseous precursors, both anthropogenic andnatural. While in the atmosphere aerosol

particles grow in size and evolve incomposition through adsorption and reactionof gases and through coagulation and canchange phase by deliquescence andefflorescence. They are removed through wetand dry deposition processes which aredependent on the composition and size of theparticles.

There are numerous activities required tounderstand and quantitatively describe theloading and properties of sub 2.5 µm particles,from generating emission inventories to

regional monitoring, to developing theknowledge of the fundamental processes thatcontrol loading of tropospheric aerosols andconcentrations of specific classes ofcompounds. The latter processes, whichconstitute what might be denoted the"atmospheric life cycle " of these aerosols,are the principal focus of TAP. A recent NRC

report called for development of advancedmathematical, modeling, and monitoring toolsto represent the relationships between specificsources of particulate matter and humanexposures and for linking sources oftoxicologically important constituents andcharacteristics of particulate matter to exposedindividuals and populations. (NRC, 1998). Butthis cannot be done without understanding ofprocesses that control these relationships.This is where DOE comes in, with expertise inatmospheric aerosol science, in conductinglarge-scale field projects, in numericalmodeling of atmospheric chemistryphenomena, and in laboratory studies andtheory. In this effort we fully expect tocomplement and leverage other federalprograms, principally those of EPA, NASA,

NOAA, and NSF. These agencies have alldeclared PM-2.5 research as a high priorityresearch focus for the near future. As hasbeen shown in the past, coordinated work bymultiple agencies is the key to real progress.

Closely related to the PM-2.5 issue is theissue of visibility impairment due to aerosols.As recently as April 22, 1999, Vice PresidentGore along with Environmental ProtectionAgency Administrator Browner announced amajor new effort to improve air quality innational parks and wilderness areas. The new

regional haze rule (Code of FederalRegulations, undated) requires states todevelop implementation plans to preventimpairment of visibility in National Parks andother pristine locations, with the objective,ultimately, of attaining natural visibilityconditions by 2064. The principal contributionto visibility impairment is from fine (sub 2.5 µmdiameter) particles, which are highly efficientscatterers of visible radiation and whoseconcentrations are closely correlated with theatmospheric light scattering coefficient (Figure2.2). Whatever the ultimate regulations thatare imposed to protect and improve visibility, itis clear that developing a strategy to achieveany such standards requires the sameunderstanding of the processes that controltropospheric aerosol loading and properties asis required to develop strategies to meet thePM-2.5 standards.



TAP Program Plan

10

Figure 2.2. Time

series of l ight

scattering coefficient

and fine particle

mass in Stockton

CA in January 1994.

Light scattering

coefficient is scaled

to fine particle mass

by daily averages.

From Husar (1997).

Another related environmental issue is aciddeposition. The recent report from theNational Acid Precipitation AssessmentProgram (NAPAP, 1998) indicates that it is tooearly to determine whether changes in aquaticecosystems have resulted from emissionreductions in response to the 1990 Clean AirAct Amendments. The report notes that overthe last 13 years New England lakes haveshown evidence of recovery from acidificationbut in contrast that the majority of Adirondack

lakes have remained fairly constant and thatthe most sensitive Adirondack lakes havecontinued to acidify. The EPA has reported to

Congress that additional reductions in sulfurand nitrogen deposition will be required to fullyrestore sensitive Adirondack lakes. Sulfateand nitrate, major components of fine particlemass (Figure 2.1) and their gaseousprecursors sulfur dioxide and nitrogen oxidesare the major contributors to acid deposition.Figure 2.3 shows that concentrations ofaerosol sulfate and of nitric acid vapor, a majoraerosol precursor, show no indication ofdecrease over the past 12 years in nonurban

regions of the Northeast.

14

12

10

8

6

4

2

0

S O 4

2 - , µ g m - 3

8

6

4

2

0

H N O 3 , µ g m - 3

98979695949392919089888786

Year

Figure 2.3. Time series of

concentrations of sulfate

aerosol and nitric acid

vapor at a site near State

College, Pa. Adapted

from NAPAP (1998), with

update from B. Hicks,

NOAA, Air Resources

Labo ra to ry (p r i va tecommunication, June

1999). Data points are 5-

week running mean of 1-

week samples.




11

Uncertainties

due to aerosols

preclude

quantitative

attribution of

climate

change over

the past

century to

industrial greenhouse

gases.

There is a

major gap in

research to

describe the

life cycle of

tropospheric

aerosols as it

pertains to radiative

forcing of

climate

change.

Lastly, research in the last decade hasindicated that aerosol particles have apotentially significant influence on radiativeenergy exchange processes in theatmosphere. Anthropogenic aerosols scatter

solar radiation and modify cloud reflectivity,thereby exerting a cooling influence onclimate. This cooling influence is thought to beoffsett ing a substantial fraction ofanthropogenic greenhouse warming, but itsmagnitude is highly uncertain. Thisuncertainty precludes confident empiricaldetection of climate change due to increasedgreenhouse gases and quantitative inferenceof climate sensitivity. It also precludesevaluation of performance of global climatemodel simulations so that it is impossible atpresent to answer the question of how much of

the 0.6 degree temperature rise over the pastcentury can be ascribed to industrialgreenhouse gases and how much to naturalvariation. Much of this uncertainty arises frompresent limited ability to quantitatively describethe aerosol loading and microphysicalproperties that govern their light scattering andcloud nucleating ability.

Shortwave radiative forcing of climate changeby aerosols by the direct and indirectmechanisms has been identified by the

Intergovernmental Panel on Climate Change(IPCC) as the greatest uncertainty in forcing ofclimate change over the industrial period(IPCC, 1996). In 1996 a NRC panel,convened at the behest of DOE, NASA,NOAA, and NSF, issued an urgent call for acoordinated program of research to quantifythis aerosol forcing (NRC, 1996). Since thattime rather little has been initiated. As we getready to face the next millennium and draft apolicy to mitigate or accommodate to theanticipated climate change, it is imperative toresolve this largest scientific uncertainty in

climate forcing.

While research programs that deal withclimate change, including the DOEAtmospheric Radiation Measurement Program(ARM, 1999; Stokes and Schwartz, 1994),examine the radiative effects of aerosols, thereis a major gap in research to quantitativelydescribe the life cycle of tropospheric aerosolsas it pertains to this radiative forcing, research

that is more properly identified as in thedomain of atmospheric chemistry and whichbuilds on the techniques and capabilities ofthis discipline. Understanding the radiativeinfluence of aerosols requires field studies that

provide a seamless link of understandingconnecting aerosol emissions, secondaryformation and evolution, chemical, physical,and optical properties, and deposition togetherwith examination of radiative influences.Ultimately what is required are models thataccurately represent aerosol loading, i.e., theamount and geographical distribution ofaerosols in the atmosphere, and the so-calledintensive properties of these aerosols, themicrophysical and optical properties thatgovern their radiative forcing per massloading. At present representation of aerosol

processes in climate modeling is in its infancy,and to the extent that this is done at all, it isdone in a quite simplistic way that does nottake into account the heterogeneity of sizeand composition that is characteristic ofaerosols. For example because of lack ofknowledge and model based representation ofaerosol composition and properties, there hasthus far been a tendency, to the extent thataerosol properties are addressed in models atall, to treat all aerosols as if they werecomposed of ammonium sulfate at 25°C.However it is known from recent results that

aerosol deliquescence and hygroscopicgrowth, and hence optical properties, dependmarkedly on composition and temperature. Itis therefore necessary to develop theknowledge base that can handle thecomplexity of actual aerosols.

It seems likely that solving the greenhouse-gas climate change issue will also require asignificant change in the nation's energyeconomy at a cost of billions of dollars.Moreover, by virtue of the fact that aerosols

couple air quality with climate change ouractions to overcome one of these challengeswill affect the other. In this context it isurgently imperative that the aerosol forcing beplaced on a much more quantitativefoundation than is available at present.

The management of these interrelatedenvironmental stresses poses a majorchallenge to decision-makers, in terms of both



TAP Program Plan

12

the atmospheric processes and themechanisms of effects on humans and theenvironment. Recently the United States EPAhas created a major goal to document thenature of ground-level airborne particles andhas challenged the health and atmosphericscience community to identify the specificatmospheric agents responsible for adverseeffects of particulate pollution [EPA, 1999b]These initiatives are superimposed oncontinuing research on visibility reducingpollution and on the influence of particles onclimate alteration. The Tropospheric AerosolProgram (TAP) will complement the initiatives

just under way in the monitoring and healtheffects areas, and add substantially to thecapabilities for advancing methods forpredicting the response of atmospheric

pollution exposure to emissions managementoptions.

2.3 The DOE Context

The fact that much of the tropospheric aerosolburden is believed to result from energyproduction and use focuses attention on thiskey component of the nation’s well-being inthe context of meeting the nation's energyrequirements in the next century.Understanding the environmental influences of

energy production and use and ways tominimize these influences is a necessarycomponent of DOE's National EnergyStrategy, which has an explicit goal to promoteenergy production and use in ways thatrespect health and environmental values—improving our health and local, regional, andglobal environmental quality (DOE, 1998a).

Referring explicitly to PM2.5 particles formerSecretary of Energy Bill Richardson hasstated, "These unseen particles may poserespiratory problems for certain portions of the

population, and for this Administration, there isno higher priority than protecting the health ofour citizens. . . At the same time, if our cleanair regulations are to be fair and scientifically-sound, we need to understand much better thelinkage between the levels of these pollutantsin the atmosphere and their sources, bothhuman and natural." (DOE, 1998b). The TAPprogram is specifically directed to developingthis understanding.

The objective of TAP should be viewed in thecontext of the national portfolio ofmeasurements and research on atmosphericaerosols. There are many elements that mustbe implemented in order to be able to meetthis country's requirements, and the severalFederal agencies have di f fer ingresponsibilities in this respect, although to besure the boundaries that separate theseresponsibilities are somewhat ill defined.EPA's responsibilities include developmentand evaluation of emission inventories ofaerosols and aerosol precursors, monitoring todetermine the extent of compliance/non-compliance with air quality standards, andepidemiological studies to quantify aerosolhealth effects. NOAA has responsibility forlong term monitoring of aerosol loading and

properties at a small number of sites. Some ofthese elements are in place now and some ofthem are being enhanced. A nationalmonitoring network will undoubtedly produceinvaluable data, but without the supportingmechanistic knowledge, its value is verylimited in providing guidance for developing anefficient control strategy or in evaluatingpresent, past, or future aerosol influences onclimate.

If the goal of a national aerosol programincludes, as it should, developing the

capability to devise effective strategies forcontrol of aerosol loadings and the ability toquantitatively estimate aerosol influences onclimate, it is essential to acquire fundamentalunderstanding of the atmospherictransformation processes governing theloading and properties of troposphericaerosols. This process-level understanding isfundamental to constructing models that aregenerally applicable, not just to a limited rangeof conditions, so that they may be applied to awide variety of situations, for examplemodeling for previous emission scenarios in

order to develop a historical record of forcing,or modeling for various emission scenarios toanswer “what if” type questions. The DOEAtmospheric Chemistry Program (ACP, 1999)has demonstrated outstanding capability toperform process-level atmospheric research.To date this program has focused largely onthe fundamental processes that controlphotochemical oxidants. TAP is viewed asquite complementary to the DOE Atmospheric

TAP must be

viewed as

one

component of

an integrated national

program of

research on

atmospheric

aerosols.




13

At present

there is

insufficient

information

about the processes

governing the

composition

and

microphysical

properties of

tropospheric

aerosols to develop

insightful

decisions to

minimize risk.

Chemistry Program and other DOE andfederal research programs.

TAP must be viewed as one component of anintegrated national program of research onatmospheric aerosols. It is essential that theprograms of the several agencies be closelycoordinated. The DOE component of thenational program is process research todetermine, quantitatively describe, andrepresent in models the mechanismsgoverning the mass loading, composition, andmicrophysical and optical properties oftropospheric aerosols, and their geographicaland vertical distribution.

TAP will contribute to the DOE/OBERresearch effort directed to understanding the

basic chemical and physical processes of theEarth's atmosphere and how these processesmay be affected by energy production anduse. This understanding will ultimately permiteffective mitigation of the long-term health andenvironmental consequences of energyproduction and contribute to optimal use ofdiffering technologies.

2.4 The Science

Context for TAP

Although recognized for some time, theimportance of tropospheric aerosols hasrecently been highlighted with respect to theirinfluence on human health (NRC, 1998) andradiative forcing of climate change (NRC,1996).

At present, despite a history of continuedatmospheric research, there is insufficientinformation about the processes governingthe composition and microphysical properties

of tropospheric aerosols available to developin a modern context insightful decisions tominimize the risk from these aerosols. Thelack of information centers in the details ofprocesses shaping the chemical compositionas a function of particle size, especiallyregarding the carbonaceous and reactivenitrogen components, both of which are majorconstituents of fine particulate matter innumerous locations (Figure 2.1).

Examination of composition of troposphericaerosol particles as a function of particle sizeindicates a wide range of variation, with muchof present-day energy related contributionsresiding in the fine particle range. Combustionprocesses tend to produce very finely dividedparticles, formed either directly in the sourceor in the air near the source. Thesenanoparticles are present in large numbersnear sources but are rapidly agglomerated inthe air.

Health effects research over the years hasindicated the importance of particle size inrespiratory disease. The fine particle fractionof the particle-composition distribution has thegreatest likelihood of affecting the lower lungs,where oxygen exchange takes place. Since

recent health studies have identified sub-2.5µm particles as a potential respiratoryinflammatory agent, there is a need tocharacterize this fraction and its growth aswell as the particle properties quantitatively forcomplex human exposure assessments. Thiskind of research is highly demanding ofmeasurement capability since it requiresscanning the particle size spectrum, whichvaries over at least three powers of ten in size,and more than seven powers of ten inconcentration.

Other hypotheses advanced by the healtheffects research community relate observedhealth impacts to specific chemical factorsincluding: metals, acids, organic compounds,biogenic particles, sulfate and nitrate salts,peroxides, soot, and gaseous cofactors(Albritton and Greenbaum, 1998). In order tomake progress in establishing which of theseagents are causative and the effects of PMcontrol measures, it is necessary tounderstand the relations between emissionsand the size-dependent composition of theambient aerosol. Thus, demands of chemical

speciation must be added to the task ofdetermining size spectra over many orders ofmagnitude. Both measurements andpredictive models are required.

The reactive nitrogen and carbonaceouscomponents are closely linked with sulfurspecies and are interactive with oxidantproduction in the troposphere. Through thework of the last two decades the chemistry



TAP Program Plan

14

governing gas-to-particle conversion of sulfurspecies is relatively well understood. Thecorresponding processes regarding particulatenitrogen and carbon are much less wellunderstood and need to be brought to a similarlevel of understanding.

Quantitative description of the reactivenitrogen (ammonia-nitrogen oxide) gas-particlecomplex is incomplete. It is critical tounderstand the response of the sulfur-nitrogen-carbon system as changes in fossilfuel blends and their combustion emissionsare mandated over the next few years. Currentknowledge cannot specify quantitatively whereall of the reactive nitrogen resides afteremission into the air. There are apparentmajor differences in the nitrate content of

aerosol particles in the eastern and westernparts of the US. These are hypothesized to berelated to conditions in which chemicalequilibrium between nitric acid and ammoniaexists in the presence of moisture, sulfate saltsand carbonaceous material. However, thisconjecture is based mainly on experience insouthern California, and is generally unverifiedfor conditions east of the Mississippi River. Asecond and equally important aspect from thehealth effects outlook is the potential fororgano-nitrate compounds to be present in fineparticles. The chemical processes in

photochemical smog are known to producegas-phase nitrate compounds that arepotential eye and skin irritants. It is suspectedbut not established that organic nitrates arealso present in particles in sufficientconcentrations to be a factor in respiratorystress, possibly being a factor in more seriousailments.

The origins and composition of carbonaceousaerosols are poorly understood, despite theimportance of carbonaceous material as afraction of aerosol mass. Evidence suggests

that carbonaceous material, as either black(elemental) carbon or as organic material,makes up as much as half of the fine particlemass concentration in air sampled in the Eastand parts of the West (Figure 2.1). Thiscomponent of aerosols has been difficult tomeasure precisely because it involves artifactsof sampling as well ambiguities of continuingexchange of semi-volatile compounds fromparticles suspended in the air.

The origins

and

composition

of

carbonaceous

aerosols are

poorly

understood,

despite their

importance

as a fraction

of aerosol

mass.

Carbonaceous material in particles derivesdirectly from combustion of fossil- and wood-based fuels. It also comes from the oxidationand subsequent condensation or adsorption ofreaction products of volatile organiccompounds. The volatiles come not only fromanthropogenic emissions but also fromexhalations from vegetation. Aside from thecomplexity of composition, two majorunknowns exist. The first concerns how muchproduction of organic material takes placefrom reactions of gaseous organiccompounds; the second concerns how muchof the secondary organic fraction derives frombiogenic sources. Some have hypothesizedthat a substantial but unknown fraction of thehaze that persists over the East in summer ismade of secondary organics, which actively

absorb moisture, as do most inorganic salts,such as ammonium sulfate and nitrate.Quantifying interactions of moisture with thecomplex mixture of organic speciesintermingled with inorganic chemicals is amajor challenge for the scientists who hope tocreate reliable mathematical models forsynthesizing scientific elements, and for airquality management.

Aerosol particles are known to be intimatelyinvolved in cloud droplet and ice particleformation and growth. At the same time cloud

and precipitation processes are instrumental inchanging the aerosol size distribution and inremoving particles from the air. The micro-physical shaping of the particle-compositionsize distribution is a complex phenomenonwhich varies with cloud macro-scaleprocesses. The sensitivity of cloud processesto aerosols has long been a subject of interestto atmospheric scientists. The quantitativecoupling of the microscale phenomena tomacroscale cloud and precipitation processesremains an unresolved problem, and thesubsequent dilution or removal of particle

populations, or the change in cloud opticalproperties is of great current interest forimprovements in air quality models, andclimate alteration calculations.

Even though progress has been substantialtowards improving mathematical methods forestimating the response of the atmosphericprocesses to changes in man’s energypractices, substantially more progress is




15

required. Progress will depend on acombination of major advances in knowledgethrough field experimentation, laboratoryinvestigations, and synthesis of informationinto mathematical models.

2.5 The TAP

Approach

Experience in atmospheric chemistry hasshown that measurements cannot besufficiently dense in space and time to meet allrequirements, nor can measurements bythemselves lead to predictive capacitynecessary for developing approaches to meetair quality requirements. The situation is evenmore complicated in the case of atmosphericaerosols, which are highly heterogeneous fromlocation to location (Figure 2.1) necessitatingprocess-level understanding and precludingthe utility of any "one size fits all" aerosolmodel. Likewise, empirical models will not betransferable to changing mix of emittedmaterials, changing atmospheric chemicalenvironment or the like.

For these reasons TAP will consist of asustained analysis and interpretation of resultssupported by a portfolio of tightly coupledresearch activities consisting of four principalcomponents:

• Field Measurements of aerosol propertiesand transformation processes.

• Modeling transport and transformation oftropospheric aerosols.

• Development of instruments and advancedmethods of aerosol characterization.

• Laboratory experiments and theory directedto aerosol processes.

The coupling of these several elements isindicated schematically in Figure 2.4. The

field program is the centerpiece of TAP. Theother elements are coupled not just to the fieldprogram but also to each other to maximizethe synergism and utility of the entire TAPProgram. These elements will enable the TAPscientific team to bring the atmosphericscience of fine particles to the level necessaryto bring informed energy and environmentalmanagement for the next several decades.

FIELD

MODELING

LABORATORY

&

THEORY

INSTRUMENTATION

& ADVANCED

CHARACTERIZATION

Figure 2.4. Science Elements of TAP.



17

TAP will develop the

fundamental

scientific

understanding

required to

construct

tools for

simulating thelife cycle of

tropospheric

aerosols--the

processes

controlling

their mass

loading,

composition,

and microphysica

properties--al

as a function

of time,

location,

altitude, and

ambient

conditions.

3. The TAP Objectives

3.1 What TAP will

Accomplish

The goal of TAP will be to develop thefundamental scientific understanding requiredto construct tools for simulating the life cycle oftropospheric aerosols--the processescontrolling their mass loading, composition,and microphysical and optical properties--allas a function of time, location, altitude, andambient conditions. The TAP approach toachieving this goal will be by conductingclosely linked field, modeling, laboratory, andtheoretical studies focused on the processescontrolling formation, size, chemicalcomposition, optical properties, transport, anddeposition of tropospheric aerosols. Thisunderstanding will be represented in modelssuitable for describing these processes on avariety of geographical scales, from tens tothousands of kilometers; developing andevaluating these models will be a key

contribution of TAP. In carrying out thesetasks TAP will work closely with otherprograms in DOE and in other Federal andstate agencies, and in the private sector,directed to related aerosol issues.

3.2 TAP Research

Tasks and Scientific

Issues

The following are examples of the principalresearch tasks and scientific issues regardingtropospheric aerosols which will beaccomplished by TAP or which the researchconducted in TAP will resolve and/or providethe physical understanding and model-basedrepresentation to permit resolution in particularsituations of interest.

• Charac ter ize the s ize-dependentcomposition, microphysical properties, andother relevant properties of atmosphericaerosols, including optical properties, at thesurface and throughout the vertical column,during TAP field projects.

• Determine the accuracy with which aerosoloptical properties (light scattering coefficient,absorption coefficient, light-scattering phasefunction) can be calculated from knowledgeof size distribution, chemical composition,

and composition-dependent properties suchas refractive index.

Determine the accuracy of emissioninventories for primary aerosols and foraerosol precursor gases in locations of TAPfield projects.

• Determine the fundamental processes thatcontrol new particle formation in theatmosphere and the dependence of therates of these processes on controllingvariables.

• Determine the processes contributing to theaccumulation of mass on pre-existingatmospheric aerosol particles and thedependence of the rates of these processeson controlling variables.

• Develop the ability to describe theinteraction of atmospheric aerosol particleswith water vapor and the dependence of thisinteraction on particle composition andsurface properties and on ambientconditions.

• Determine the rate of dry deposition as aremoval process for aerosol mass andnumber and its dependence on particle sizeand composition.

• Determine the influence of meteorologicalprocesses, such as turbulent mixing inconvective systems and accumulation inhigh- and low-pressure systems, in-cloudreactions, precipitation scavenging, on



TAP Program Plan

18

temporal variation of aerosol loading andproperties.

• Determine the influence of aerosol loadingand properties on gas phase chemistry assites of heterogeneous catalytic reactions,

as sinks of gas-phase species, and bychanging the actinic flux.

• Develop model-based tools to determine thefraction of the aerosol mass observed at agiven location that derives from primaryemissions versus gas to particle conversionin the atmosphere.

• Develop model-based tools to determine thefraction of aerosol mass at a given locationthat is anthropogenic versus natural.

• Determine the geographical and verticalscale that is required for physical simulationmodels to describe PM-2.5 exceedances.

• Determine the spatial and temporalresolution required in models to representaerosol loadings and properties on aregional scale in order to provide realisticestimations of effects of emission control.

• Determine the computing power required torepresent aerosol loading, and size resolvedchemical, and physical properties insimulation models.

• Develop methods to parameterize aerosolprocesses in regional to continental scaleair-quality models and in global scale climatemodels.

• Determine the accuracy with which physicalsimulation models describe aerosol loading,

composition, size distribution and opticalproperties.



19

4. Organizational Structure

4.1 Organizational

Elements of TAP

The organizational structure of TAP isdesigned to meet the needs of a complexscientific research program that will consist ofindividual research projects all directed to acommon set of goals, and to being responsiveto the management requirements of DOE.

The management and organizational structurefor the program as presently envisioned issketched in Figure 4.1. The major features ofthe program's organization are as follows.

1. Direct management of the Program by aProgram Director in the EnvironmentalSciences Division of DOE's Office ofBiological and Environmental Research.

2. Interagency Coordination, primarily throughthe Federal Air Quality ResearchSubcommittee (AQRS) and the variousNARSTO working groups, to ensure closecoordination with other programs.

3. A Lead Scientist, who must be an aerosolscientist with broad experience, will haveoverall responsibility for the implementationof TAP, with consultation with DOE andwith the Scientific Steering Committee, forthe scientific leadership of the program and

for representing the program within thescientific community.

4. The Science Team will consist of thePrincipal Investigators of the scientificprojects comprising TAP. Science projectswill be selected competitively throughproposals in response to DOE ProgramAnnouncements, or through jointannouncements with other agencies.

Tropospheric Aerosol Program

Science Support Team

DOE

EnvironmentalSciences Division

InteragencyCoordination

Lead Scientist

Science Team Investigators

Steering Committee

Field Investigators Team

Chief of Operations

NARSTO

TAP Project Support

Science Support

Management Team

Science TeamScience Support

Executive

SteeringCommittee

WorkingGroups

Figure 4.1. Organizational structure of TAP including DOE management oversight and Interagency

Coordination, and showing linkage to the national research effort on tropospheric aerosols through

NARSTO.



Organizational Structure

21

TAP will be

closely linkedto ongoing

DOE projects

dealing with

the

environmenta

influence of

energy

activities.

TAP

complements

these

programs by

focusing on

the processes

that control

the loading,

geographical distribution,

chemical

composition

and

microphysical

properties of

tropospheric

aerosols,

especially

anthropogenic

aerosols.

4.4 Integration

An underlying philosophical tenet of TAP isthat good science must undergo the scrutiny of

peer review, in the selection of projects and inthe publication of the findings of research.Traditionally in science the latter is throughpeer-reviewed journals, and this will certainlybe a requirement for TAP investigators. It mayreasonably be anticipated that over theduration of this program such publication willincreasingly be by means of electronicpublications, which are already beingimplemented in the geophysical sciences, andwhich maintain the rigorous requirements ofpeer review while at the same time permitpublication of much richer data sets and even

the dynamics of models, in contrast to thestatic format of traditional paper journals. TAPwill actively encourage publication of findingsin such media. TAP will also provide a web-based server to facilitate dissemination ofpublications reporting TAP research. Thisweb site will serve as an active vehicle forcommunication among TAP investigators, forplanning of field programs, for exchange ofdata and models, for preparation of reports,and for active exchange of ideas that willmake TAP a truly collaborative program.

As a mission-oriented program, TAP has aresponsibility to DOE to make its findingsavailable to the user community in a way thatwill maximize the utility and use of thesefindings. A specific example is models. Theseshould be made available in readily accessibleelectronic format that will allow their use by theexternal scientific and air quality managementcommunity. Likewise, many of the fieldmeasurement data of TAP will be of broadinterest not just to TAP investigators but alsoto a variety of outside entities. To this end

TAP will facilitate dissemination of researchresults by suitable web-based approaches.

TAP will conform to the data managementpolicy of the U.S. Global Change ResearchProgram (USGCRP, 1991). This policy callsfor continuing commitment to theestablishment, maintenance, validation,description, accessibility, and distribution ofhigh-quality, long-term data sets, full and open

sharing of data, preservation of data, inclusionin data archives of information about the dataholdings, including quality assessments,supporting ancillary information, and guidanceand aids for locating and obtaining the data,adherence to data dissemination standards,and timely availability of data subject to areasonable period of exclusive use byprogram investigators.

4.5 Oversight and

Interagency

Coordination

Overall management responsibility for the

Tropospheric Aerosol Program (TAP) isprovided by the DOE Program Director.

Oversight is provided by DOE’s EnvironmentalSciences Division (ESD), Office of Biologicaland Environmental Research (OBER), and theBiological and Environmental ResearchAdvisory Committee (BERAC).

Interagency coordination is provided throughthe Federal Air Quality ResearchSubcommittee (AQRS), the AtmosphericChemistry Panel of the Federal Subcommittee

on Global Change Research (SGCR), and aninteragency Aerosol Working Group.

4.6 Relation to Other

DOE Programs

TAP will be closely linked to ongoing DOEprojects dealing with the environmentalinfluence of energy activities. TheAtmospheric Chemistry Program deals with

regional to global scale global chemistry andfate of tropospheric air pollutants. TheEnvironmental Meteorology Program dealswith measurement and modeling of verticaltransport and mixing processes in the lowestfew kilometers of the atmosphere. TheAtmospheric Radiation Measurement Programis aimed at improving the understanding of thetransfer of solar and terrestrial infraredradiation in the atmosphere, and the



TAP Program Plan

22

atmospheric properties controlling thisradiation transfer and the representation ofradiation transfer in climate models in thecontext of the necessity to represent climatechange due to anthropogenic greenhousegases and aerosols.

The TAP program complements theseprograms by focusing on the processes thatcontrol the loading, geographical distribution,chemical composition and microphysicalproperties of tropospheric aerosols, especiallyanthropogenic aerosols. Specifically, TAPfocuses on atmospheric transformationprocesses governing the composition oftropospheric aerosols especially gas-to-particle conversion in the atmosphere,nucleation of new particles, growth of existing

particles, and how these processes affectaerosol composition and properties.

Atmospheric Chemistry Program (ACP).The ACP consists of a set of research projectsfocusing on chemistry and fate of troposphericair pollutants including aerosols on regional toglobal scales (ACP, 1999). Much ACP fieldwork is directed to atmospheric oxidants andrelated free radicals. Because of the strongcoupling of oxidant and aerosol chemistry, it isexpected that some field projects in TAP maybe conducted in conjunction with ACP field

projects to take advantage of chemical andmeteorological measurements that arepertinent to the requirements of both projects.

Atmospheric Radiation Measurement(ARM) Program. The Atmospheric RadiationMeasurement (ARM) Program is directed tomeasurement and model based representationof radiative transfer in the earth's atmosphereand to the processes controlling radiationtransfer, principally involving water vapor andclouds, and to lesser extent aerosols (ARM,1999; Stokes and Schwartz, 1994). The ARM

program maintains a highly instrumented sitein north central Oklahoma at which a variety ofmeasurements are employed to providedetailed characterization of the atmosphericstate and meteorological variables that controlthe evolution of the atmospheric state.continuous measurements also includeaerosol optical depth (during the daylighthours when the sun is visible, verticaldistribution of aerosol, by Lidar, and aerosol

optical properties and limited chemicalvariables at the surface. Because of thesemeasurements it may be quite attractive toconduct one or more TAP field studies at theARM Oklahoma site.

Environmental Meteorology Program. Themeasurement and modeling of verticaltransport and mixing processes in the lowestfew kilometers of the atmosphere areproblems of fundamental importance and ofmuch practical importance governing theaccumulation of air pollutants, for which a fullysatisfactory treatment has yet to be achieved.In recognition of this DOE ESD has recentlyinitiated a Vertical Transport and MixingProgram (VTMX, 1998) directed toinvestigation of vertical transport and mixing

processes in the lower atmosphere,concentrating on processes in stably stratifiedconditions, in conditions of weak or intermittentturbulence, and during morning and eveningperiods that mark transitions between stableand convective conditions with particularinterest in urban regions affected by adjacentelevated terrain (e.g., urban basins or valleys).Because of the necessity for detailedcharacterization of the meteorological situationat the times of TAP measurements it isparticularly attractive to consider conductingTAP field campaigns in conjunction with VTMX

field campaigns.

DOE Research Aircraft Facil i ty.Measurements aloft are critical to the successof TAP. A Gulfstream 159 (G-1) aircraft (DOEResearch Aircraft Facility, 1998), outfitted withinstrumentation for trace gas, aerosol, andmeteorological measurements, can bedeployed to field study locations. With a rangeof ~1,600 km and duration of ~4.5 hours, it canprovide spatial distributions of ambientvariables at altitudes from ~300 m to ~7.5 kmacross the regional scale of interest to TAP.The facility can also be used to flight test newinstrumentation systems developed withinTAP.

DOE Environmental Molecular SciencesLaboratory (EMSL). The EMSL is a nationalscientific user facility whose mission is toprovide advanced and unique resources toscientists engaged in research on critical



Organizational Structure

23

environmental problems. It includescapabilities that are particularly well suited forresearch on the detection of aerosolprecursors, and on formation, growth,reactivity, and surface and bulk speciescharacterization for natural and modelaerosols. It also provides massively parallelcomputational capabilities well suited toatmospheric sciences research. Thesefacilities (EMSL, 1999) are available withoutcharge for nonproprietary research.

DOE National Energy TechnologyLaboratory (NETL) Upper Ohio River ValleyStudy. In this study (DOE, 1998b) fourmonitoring sites in the region are beingequipped with a broad array of sophisticatedequipment, both commercially-available and

still-experimental monitoring devices, to collectand analyze the small particles. Two of thelocations will be so-called "supersites" and willbe outfitted with devices to measure thechemical make-up, size and seasonalvariations of the airborne particles. At each"supersite," meteorological data, such as windspeed and direction, relative humidity, andultra-violet radiation, also will be gathered.

DOE NETL "Fingerprint" study. This study(DOE, 1998c) will examine whether fineparticulate emissions from coal-burning

systems have unique "fingerprints" that canidentify their source. Researchers will tracethe physical and chemical properties of PM2.5to the properties of the coal burned, theoperating conditions of the combustor andboiler, and the configuration and operation ofpollution control technologies.

DOE Office of Heavy Vehicle Technologies'Diesel Particulate Sampling Methodologyproject. This project is motivated by the newPM-2.5 NAAQS and alternative fuels. Theproject involves determining actual particle

size distribution and particle numberconcentrations in the exhaust plumes fromheavy-duty diesel vehicles operated on theroad. Data are then compared with datagenerated at emission test facilities todetermine if current sampling and analysismethods are adequate for characterizingparticle size and number. Then in order todetermine the zone of influence of theseemissions from a roadway, particle

transformations are examined as the plumedisperses downwind of the roadway in typicalurban situations.

Accelerated Climate Prediction Initiative.The Accelerated Climate Prediction Initiative(ACPI, 1998), sponsored in part byDOE/OBER, responds to a need within theUnited States to produce the projections ofclimate variability and climate changenecessary for the U.S. to participate ininternational assessments of climate change,as well as to understand the regional andnational effects of global change. The promiseof dramatic improvements in computationalcapabilities and simulation science affords theglobal modeling community an opportunity tomake breakthroughs in understanding and

projecting long-term changes in the globalenvironment. Because of the radiative forcingof climate change due to anthropogenicaerosols and the need to represent thisclimate influence in climate models, it may beanticipated that aerosol modeling will be acomponent of the ACPI. The scientificunderstanding developed in TAP will be ofdirect and immediate relevance to thatmodeling effort.

4.7 Relation to Other

Federal Programs

Because of the widespread recognition of theimportance of tropospheric aerosols there ismuch interest in the several agenciesresponsible for air quality and global change indeveloping enhanced scientific understandingand model-based representation of theprocesses controlling the mass loading andchemical and microphysical properties oftropospheric aerosols. Several agencies have

substantial research programs examiningvarious aspects of the tropospheric aerosolissue. These are briefly summarized inAppendix C. Reference should be made alsoto the compilation of particulate matterresearch activities in the United States ismaintained by the Health Effects Institute (HEI,2001). In this context it is the explicit intent ofTAP both to be complementary to theseprograms and to cooperate with these



TAP Program Plan

24

programs to the mutual benefit of the severalprograms and the nation.

In view of the intense interest in troposphericaerosols there is already strong interactionand cooperation among the several agenciesat both the agency level and at the workingscientist level. At the agency level, thisinteraction occurs in the Air Quality ResearchSubcommittee and in the Subcommittee onGlobal Change Research, and in theExecutive Steering Committee of NARSTO, inall of which DOE plays an active role, as dothe other cognizant agencies. At the workinglevel, there are strong bonds that have beenforged between DOE ESD programs and thecorresponding programs in NOAA and EPA,as well as with researchers supported by NSF.

These working-level interactions have beenmanifested in the past in jointly conducted fieldprograms, most recently in the SouthernOxidant Study. There are also strong ties toaerosol research conducted in support ofglobal change research by pertinent offices ofNOAA and NASA that have been manifestedin joint modeling activities and in activecollaboration in use of ground-based andsatellite data pertinent to aerosols. It may beaccurately stated that these cooperativeactivities have led to a whole that well exceedsthe sum of the parts in terms of the value of

the research and even more so in terms ofvalue per money expended.

It is wholly to be expected that connectionssuch as these will continue into the future andeven be strengthened. The problem oftropospheric aerosols is not only an importantone; it is also a very difficult one.Consequently it may be anticipated that TAPField Campaigns will be conducted jointly withfield campaigns of other organizations,including states and the private sector, to thebenefit of all parties. More specifically, asEPA establishes its several "supersites" fordetailed characterization of aerosols andaerosol precursor gases (EPA, 2000), thepresence of these sites will make theselocations attractive for conduct of TAP FieldCampaigns.

TAP interactions with the programs of other

agencies will be further strengthened byparticipation on the Steering Committee of theTAP Science Team of scientists from theseveral other agencies. This participation willbe especially valuable as the SteeringCommittee undertakes periodic reviews of thecomponents of TAP in order to ensure thatnecessary gaps in knowledge are being filled,and if not, what new program componentsmust be added to TAP. It may be hoped aswell that the Steering Committee can workwith corresponding entities in other Agencies,for example to ensure compatibility of

methods, maximum utility and utilization ofdata, and sharing and intercomparing models.



25

TAP field

measurements

will be

centered in intensive field

campaigns

examining

aerosol mass

loading and

chemical and

microphysica

properties

and the

evolution of

these

quantities.

5. Science Implementation

5.1 Field

MeasurementsTAP Field Measurements will be centered inintensive Field Campaigns of limited durationdirected to the examination of aerosol massloading and chemical and microphysicalproperties and to the evolution of thesequantities through atmospheric processes.Abundant experience in studies of

atmospheric chemistry has shown that onlythrough field measurements can confidencebe developed in the physical understandingand model representation of processesresponsible for evolution of chemicalsubstances in the atmosphere.

Each campaign will use a suite ofsophisticated instrumentation deployed at anarray of surface sites in combination withsystematic in-situ measurements aloft byaircraft borne instrumentation and with remotesensing from the surface, aircraft, and

satellites. These measurements will besupported by a network of sites that willprovide meteorological data such as winds,mixing heights, and similar parametersnecessary to characterize atmospherictransport.

Experience has shown that importantadvances in understanding of atmosphericchemical processes occur through the study ofcontrasts. Therefore field campaigns will beconducted in multiple locations, characterizedby different climate, geography, and industrial

and natural emissions, and at different times ofthe year. It is intended that TAP will conductcomprehensive field intensives at roughly one-year intervals.

In order to augment the measurementsprovided by TAP it is intended that TAP fieldcampaigns take advantage of existingmonitoring networks and specialized siteswhere measurements of particles and reactivegas concentrations are made, and of other

field programs carried out by organizationshaving similar goals. In some cases it may beadvantageous for TAP to join forces with thephotochemical oxidant or boundary-layermeteorology community, thereby takingadvantage of a common need for chemicaland/or meteorological information. Thisapproach clearly calls for a program that hasthe flexibility to conduct campaigns inlocations in which other mutually contributingactivities are taking place.

In addition to these large scale comprehensivefield programs, there will be opportunitieswithin TAP for smaller scale, more narrowlyfocused field studies. These might, forexample, be directed at instrument evaluation,the testing of specific hypothesis, orsupplementing the measurement capabilitiesof a long term monitoring site. Finally, TAPshould be prepared to rapidly respond tomajor haze episodes, fires, or dust events,which can provide unique opportunities forstudying aerosol processes. Studies duringsuch events with support by forecasting,

regional modeling, satellite monitoring, andcontinuous surface data will lead to rapidadvances in understanding.

TAP Field Campaigns

Major field campaigns will extend for typically4 to 6 weeks, a time period adequate for theaccumulation of a statistically sound data basethat depends on sampling multiple 5- to 7-daysynoptic cycles. This time period is also withinthe endurance time-frame for scientists andsupport staff to be in the field, and is

affordable within anticipated resources. Afurther consideration governing the frequencyof field campaigns is the necessity for time toanalyze, interpret, and model the results froma given campaign, and to prepare reports offindings for publication in the scientificliterature.

In the past, especially in the photo-oxidantresearch community, campaigns have



TAP Program Plan

26

typically been conducted primarily during thesummer, to take advantage of heightenedphotochemical oxidant activity as well as theavailability of university researchers.However, it is necessary also to conductcampaigns during other seasons, for example,to study the winter "brown cloud" that ischaracteristic in certain urban regions.

A given field study will focus on a geographicalarea of limited extent but will be designed toaddress multiple scientific objectives, forexample aerosol evolution in power-plantplumes or plumes from isolated urban areas.Other scientific objectives might includeexaminations of the role of cloud processes inthe formation of aerosol mass or thegeneration of new particles. Typically, fieldobservations will be centered on an urbanarea. The spatial scale will extend from theurban center, the location of most intenseemissions and photochemical activity to moreregionally representative non-urban locationstypically about 200 km. This spatial scaleencompasses emissions of aerosol precursorgases, intense secondary photochemistryleading to gas-to-particle conversion andformation of new particles and growth of pre-existing particles. Study over this spatial scalealso permits quantification of the export ofaerosols out of the source region; this export is

responsible for so-called regional backgroundlevels. Measurements conducted on suchscales will also allow for targeted studies suchas particle formation and growth in power plantplumes, cloud process studies, and aerosolremoval by wet and dry deposition.

A combination of airborne and surface-basedmeasurements will be used. Figure 5.1 showsa schematic of the deployment of thesemeasurement facilities. Shown in the figureare a central site ("supersite") at which themost detailed observations will be made.

Measurements will be made by both in-situand remote sensing instruments. Thissupersite will be augmented by several,typically 6, supplementary sites ("satellitesites") where a more limited set ofmeasurements will be made to provideinformation on the spatial variation of aerosolsand key precursor gases. Surface-basedmeasurements will be supplemented byaircraft carrying in-situ and remote sensing

A given field study will

address

multiple

scientific

objectives.

instrumentation to provide information aboutthe vertical and horizontal distributions ofaerosols and precursor gases.

In addition to the chemical and microphysicalinformation obtained by aircraft and surface

measurements, it is essential to characterizethe flow fields and vertical structure of theatmosphere to permit interpretation of themeasurements. These measurements arealso required as input to mesoscale models. Anetwork of specialized meteorologicalinstruments will be deployed to conduct suchmeasurements. Addit ionally pertinentmeteorological data will be acquired fromexternal data sources.

Field Program Planning

and ImplementationPlanning and implementing a large scale andcomplex field program such as TAP is acomplicated task. An inherent problem isproviding sufficient and sufficiently well defineddata to usefully address the broad range ofscientific issues that need to be addressed bythe program. Allocation of sufficient resourcesfor field studies is a continuing problem.

A way of addressing these concerns that hasbeen effectively used in other programs is the

so-called "mentoring" concept, and it issuggested that this concept be used in TAP.In this model the broad scientific objectives ofthe program will be defined by the TAP FieldInvestigators Team. A subset of thesescientists will then be selected as mentors todesign and represent specific studies to beconducted as a part of the Field Campaign.Mentors will form teams of scientists withsimilar interests to specify the measurements,strategies for use of aircraft and similar factorsthat are required to achieve their objectives.The set of studies developed by the mentors

will constitute the Scientific Plan for a givenfield program. During conduct of the program,the committee of mentors will be responsiblefor the day-to-day planning, converting themeasurement requirements into a set of plansthat best uses the deployable resources suchas aircraft and surface measurement facilitiesunder a given set of meteorological conditions.Mentors will also be responsible for initiatingand coordinating subsequent data analysis. A

Field

Campaigns

will be

centered on

an urban

area extending to

more

regionally

representative

non-urban

locations,

typically

about 200 km.



Science Implementation

27

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Figure 5.1. Schematic Diagram of TAP Field Campaign. Supersite (center) provides detailed characterization

of aerosols, precursor gases, and meteorological variables by in-situ measurements and remote sensingcontinuously over the 6-week campaign. An array of satellite sites provides continuous information on the

spatial variation of these quantities, but with less detail. Measurements with fixed-wing aircraft and

helicopters provide in-situ and remote sensing information on the vertical and horizontal distributions of these

quantities. Satellite observations provide an overview of the large scale distribution of aerosols and synoptic-

scale meteorology.

field program manager will be responsible foroverall coordination of the Field Campaign,overseeing the planning process, andprocuring resources for the study, and willpreside over the campaign itself. An importantfunction of the field program manager will be

to assure that all of the mentors obtain anadequate share of the available resourcesduring the campaign.

Measurement Strategies

A detailed set of measurement strategies willbe developed for each field program andsummarized and made available to TAPinvestigators and other participants in the form

of a Field Program Science Plan. Specificstrategies will be determined by the set ofobjectives to be addressed in a given program.Defining how, when and where these studieswill be conducted will be the responsibility ofthe TAP Field Investigators Team (see Figure

4.1).

The overall strategy of TAP field programdesign will be to provide a structure and basicset of measurements so that the specificobjectives of a given Field Campaign can beachieved. At minimum it is anticipated thatTAP will provide a continuous description ofthe concentration and composition of aerosols,aerosol precursors and other relevant species,



TAP Program Plan

28

as a function of time, location and altitudewithin the project area as an integral part ofeach Field Campaign.

This description of aerosols and precursorgases will be accompanied by an equallydetailed characterization of the meteorology.In addition to mean winds the measurementsmust include turbulent fluxes, boundary layergrowth, fair weather cloud formation, cloudevolution and microphysics, vertical transportand mixing processes, differential advection oftemperature and humidity, atmosphericstability, and entrainment. Although TAPmeasurements will typically be limited to a200-km domain, it will be necessary to takeinto account the influence of synoptic-scaleprocesses on transport of aerosols and

aerosol precursors into and out of the studyarea. These baseline data are required bothto provide the context within whichmeasurements can be interpreted and to driveand evaluate mesoscale models of aerosolloading and transport.

A strategy for deploying surface sites that hasbeen used successfully in field campaignsexamining photochemical oxidant formation isto perform detailed measurements at aprimary site and to augment thesemeasurements by a network of satellite sites.

This is the approach that will be taken in TAP,as indicated schematically in Figure 5.1.

The TAP supersite will deploy acomprehensive suite of instruments that willgive rise to a comprehensive set ofmeasurements of aerosols, aerosol precursorgases and other controlling or diagnosticatmospheric chemistry variables, such asactinic flux. This suite of instruments will becentered on one-of-a-kind devices that extendthe state of the measurement art or which areso scarce or costly to use, that they can be

deployed only at a small number of sites.Baseline measurements at these primary siteswill include O3 and O3 precursors such as NO,NO2, NOy, and volatile organic compounds,VOCs; aerosol precursors such as SO2;photochemical intermediates such asformaldehyde, and product species such asHNO3 and peroxides. Aerosol characterizationmeasurements will include microphysicalproperties (e.g. size distributions from 3 nm to

The

description of

aerosols and

precursor

gases will be accompanied

by an equally

detailed

description of

the

meteorology.

10 µm), coarse and fine bulk composition,size-resolved composition, aerosol mass, andmulti-wavelength aerosol light scattering andoptical thickness. Examples of specializedinstruments include single-particle massspectrometers, Lidars for measuring thevertical distribution of aerosols and watervapor, and mass-spectrometric instrumentstailored to the measurement of gas-phaseH2SO4 and NH3. These measurements willbe supported by a full complement ofmeteorological measurements including radio-acoustic sounder wind profilers.

Satellite sites will necessarily have lessextensive measuring capabilities, but as theywill be less costly to establish and operate,they can be placed in more locations. These

sites will be used to measure the mostimportant gas-phase species and provide acoarser description of aerosol composition andsize distribution. Where possible TAP willmake use of aerosol and gas measurementsfrom air quality measurement sites maintainedby state or regional agencies.

A possible siting strategy for TAP will be tolocate the supersite immediately downwind ofan urban center to characterize the emissionsfrom the city into the downwind domain and tostudy fast conversion processes. Satellite

sites will be located at several upwind anddownwind distances and/or at locations inchemically different environments (e.g.,coastal, forested) within a 200 kmmeasurement domain. The number anddisposition of sites within a project area willvary from campaign to campaign, as eachstudy location will have a unique set ofcharacteristics that will need to be addressedin the field campaign design.

Essential to many process level studies arethe time variation of winds and boundary layer

height needed to determine dilution and toinfer the time scale over which reaction andaerosol evolution have occurred.. These dataare also required for driving regional scalemodels used to calculate concentration fields.To meet these requirements a network ofmeteorological instruments will be deployed toprovide information on wind fields, boundarylayer height and other important parameters.Wind fields will be measured with a network of




29

Figure 5.2. Deployment of surface sites for measurement of chemical constituents, wind

flows, and surface fluxes in the Southern Oxidants Study 1999 Nashville Experiment.

From SOS (1999).

Radio Acoustic Sounding Systems (RASS).These will be supplemented by periodicrelease of radiosondes. The wind profilers willbe located at sites where chemical andaerosol properties are also measured, therebyenhancing the value of both measurements. Aparticularly useful set of measurements will beobtained by co-locating a RASS with a Lidarmeasuring aerosol vertical profiles. Thiscombination will provide the meteorologicalcontext needed to interpret variations inaerosol vertical profiles and the concurrentsurface- and aircraft-based measurements ofaerosol properties. The number anddisposition of meteorological instruments foreach of the Field Campaigns will be dependon the location in which the campaigns areconducted. Locations which exhibit complex

meteorology (e. g. coastal locations with sea-breeze circulation or locations in complex

terrain) will require a fairly dense network ofmeasurements. Locations with relativelysimple meteorology will require fewer sites.

An example of a deployment strategy forsurface sites that may serve as a useful modelfor TAP Field Campaigns is that used in theSouthern Oxidant Study Summer 1999Nashville Intensive, Figure 5.2. The focalpoint of the surface network (corresponding toa TAP "supersite") is located just to thenortheast of downtown Nashville, where anextensive set of instrumentation permitsdetailed characterization of the rate of ozoneformation and the important factors controllingthis rate. The site was selected to be at ornear the point of maximum ozone formationunder prevailing wind conditions. A site in

downtown Nashville is used to document theurban source signature. An additional site



TAP Program Plan

30

northwest of the city (in the prevailing upwinddirection) characterizes the background air.

Similar considerations will guide the placementof sites in TAP except that the principal focus

will be aerosols rather than photochemicalspecies, and the time/distance scales may besomewhat different.

Instrumented research aircraft will be anintegral component of TAP Field Campaigns.They will perform a variety of studies notpossible with either surface-based or remote-sensing measurements. Examples includeparticle formation and evolution in plumes,c loud process studies, regionalcharacterization measurements, and opticalclosure experiments. Use of multiple aircraft is

planned. A slow-flying fixed wing aircraft orhelicopter is needed for measurements ofsource characteristics. A large aircraftequipped with a full complement ofinstrumentation for measurement of aerosolprecursors, intermediates, and productspecies, and aerosol and cloud microphysicswill be needed for plume studies, cloudprocess studies, and regional characterizationmeasurements. The in-situ measurements ofthese aircraft will need to be supplemented byan aircraft equipped with instrumentation forremote sensing of quantities such as thevertical distributions of aerosols, water vapor,and photochemical species such as O3.These measurements will allow quantitiessuch as the vertical and horizontal dispersionof plumes from urban and point sources to bedetermined. In the past, coordinated remote-sensing and in-situ aircraft measurementshave been extraordinarily valuable, with theremote sensing measurements providing acontext within which the in-situ measurementsare interpreted.

Detailed strategies for deployment of aircraftand other resources will be developed by theTAP Field Investigators Team as part of theplanning activity for each Field Campaign.The following paragraphs present examples ofstrategies that have been used in previousstudies and which will form a basis fordeveloping measurement strategies in TAP.One previously employed strategy foreffectively studying oxidant formation has

Instrumented

research

aircraft will be

an integral

component of TAP Field

Campaigns.

They will

perform a

variety of

studies not

possible with

either surface-

based or

remote-

sensing

measurements.

been urban plume studies, and it is anticipatedthat many features of aerosol formation andgrowth can also be studied in urban plumes.Aircraft are the ideal platform for such studiesowing to their ability to rapidly sample largedistances. Sampling would be done upwind ofthe source region, over the source region, andin the plume emanating from the source atvarious times (distances) downwind. Anexample of such a flight pattern used to studythe evolution of the chemical andmicrophysical properties of several powerplant plumes during the Summer 1995Southern Oxidant Study Nashville Intensive isshown in Figure 5.3.

The upwind and source region flight segmentsserve to quantify inputs into the plume frombackground air and from the source itself.Wind speed is used to convert a knowndownwind distance to an atmospheric reactiontime, thereby permitting the observed changesin aerosol properties to be expressed in termsof rates. Of particular interest are the rates ofgas-to-particle conversion of various species,how this conversion adds to aerosol mass,and associated changes in the particle numberand mass size distributions . Themeasurements made on the aircraft will beused to relate these rates to gas-phaseprocesses.

Although such studies can in principle be donein a Lagrangian framework, in which a specificair parcel is intercepted at various downwinddistances, consideration of the time anddistance scales suggests that a trueLagrangian study would be operationally verydifficult to achieve. Under favorable conditionsa plume from an urban or power plant sourcecan be tracked for about 200 km. For a typicalboundary-layer wind speed of 20 km h-1,measurements over a 200 km distance wouldallow chemical and microphysical changes to

be tracked for the important initial 10 hours ofthe material's lifetime in atmosphere. A trueLagrangian study encompassing such a timespan would require measurements made overa 10 hour period, considerably greater thanaircraft endurance will allow. Multiple flightsand/or multiple aircraft can be used to bypassthis sampling incompatibility. However,experience by the photochemical communitytracking urban and power plant plumes




31

Figure 5.3. Example of typical flight path executed by research aircraft in the study

of oxidant formation in power plant plume in the vicinity of Nashville TN. The color

code identifies the flight track of the aircraft (green) and the various point sources in

the region, the direction of their plumes and the plume-crossings by the aircraft.

The estimated relative magnitude of the various sources of NOx are listed in the

box. From SOS (1998).

suggests that not much information is lost byoperating in a quasi-Lagrangian mode, inwhich the requirement of sampling in the sameair parcel is relaxed. Plume traverses can thenbe done on air parcels that passed over thesource region at any time within a several hourperiod. An example of the evolution of aerosolsize distribution from a power plant plumestudy using a similar strategy is shown in

Figure 5.4.

Development of a quantitative understandingof aerosol formation in urban and power plantplumes will be greatly enhanced by theaddition of two additional elements, concurrentrelease of an inert tracer, and synchronized (tothe in-situ aircraft) overflights by an aircraftwith the ability to remotely sense the verticaldistribution of aerosols. Release of tracers

concurrent with the experiment allows a muchmore quantitative assessment of the rates oftransformation processes to be developed, aslosses of substances from the plume, anddilution can be accounted for by ratioingconcentrations to the concentration of the inerttracer. The technology for releasing tracersfrom such point sources and for measuringthem from aircraft platforms is well developed

and available for use in TAP. (Koffi et al.,1998).

Over-flights with a remote sensing aircraft andpassive sensing of aerosols by geostationarysatellites provide essential contextualinformation for interpretation of the in-situ data.Because in-situ aircraft measurements provideonly sparse sampling of a feature such as aplume, there is generally no way of knowing



TAP Program Plan

32

a

b

c

Dp, µm

Figure 5.4. Aerosol volume-size distribution

at 16 km (a) and 23 km (b) downwind in the

plume of the Cumberland power plant in

Tennessee, after background subtraction, and

in background air (c). Note growth of volume

in size 0.1 to 1 µm. Source McMurry et al.,

1981.

from such measurements which portion of theplume is being sampled. As a result it is notpossible to infer the influence of spatialinhomogeneities on aerosol evolution. Theresultant uncertainties can be greatly reducedby using information on the context of the in-situ measurements relative to the plume as awhole. Such measurements can be made witha down-looking aerosol Lidar on a secondaircraft overflying the plume.

Different strategies will be used to study otherprocesses such as the interactions of cloudsand aerosols. Clouds play an important role indetermining the physical and chemicalproperties of ambient particulate matter.Particles increase their mass and change theircomposition and physical properties through

in-cloud gas-to-particle conversion processesassociated with aqueous-phase reactions.Cloud droplet aggregation and precipitationexert major influences on the evolution ofaerosol size distributions. New particles canbe formed near the tops of clouds when pre-existing aerosol surface area is depleted andphotochemically active gas phase precursorconcentrations are high.

Cloud sampling (other than for fog) will beaccomplished by in-situ aircraft sampling. Thegeneralized cloud sampling strategy will be to

characterize the trace gas, aerosolcomposition, and microphysical properties ofair in the cloud inflow region, measure thecomposition of cloud water and cloudinterstitial air, and to characterize themicrophysical properties of the cloud atvarious altitudes within cloud. The chemicaland microphysical properties of the air in thecloud outflow region will also be measured.Analysis of the relationships between the

Sampling

strategies will

be developed

to test

emissions

inventories.

properties of the inflow air, cloud water andinterstitial cloud air composition andmicrophysical properties, and similarproperties in the cloud outflow air will providekey information on the role of clouds inmodifying aerosol properties. Such flights mayalso provide key information regarding theconditions under which new particle formationoccurs. Cloud studies would greatly benefitfrom measurements with co-located cloudradars, which can define the physicalboundaries of the sampled clouds, as well asprovide information about cloud dynamicalprocesses that are key to understandingcloud-aerosol interactions.

Sampling strategies will also be developed totest emissions inventories. Emissions

characterization, including the continueddevelopment of emissions estimation systems,continues to be a critical element of reliable airquality modeling, but generally has receivedlow priority in apportioning resources in fieldcampaigns. Further progress in understandingof tropospheric aerosols through interpretationof models depends critically on substantiallyimproving emissions estimates. In thesimplest form, these tests will be performed bycomparing observed ratios of aerosolcomponents with inventory predictions. Thiscomparison is one of the few ways in which

emission inventories can be tested. Testingand/or development of emissions inventorieswill require the development new methods toefficiently obtain, by analysis of data andactivity patterns, emissions information ondaily to hourly time scales commensurate withthe requirements of the physical and chemicalprocesses taking place in the study zones.Emissions data for stationary sources of sulfuroxides, nitrogen oxides and VOCs will be




33

The

instrument

suite to be

deployed in a

given TAP Field

Campaign wil

be determined

during the

campaign

planning

process.

needed along with transportation data. Anequally important need will be ammoniaemissions data, from sources quite differentfrom the others, including natural andagricultural categories.

Measurements andPlatforms

The instrument suite that will be employed in agiven TAP Field Campaign will be determinedduring the campaign planning process. To agreat extent the availability of instruments andtheir operational characteristics such as timeresponse and sensitivity will determine fieldmeasurement design. Some of the requiredinstruments are available, are well calibratedand have operational characteristics that are

well understood. Other instruments will needto be improved so that their time response,sensitivity, or specificity are adequate for theirintended use, e. g. aircraft deployment. Someinstruments will need to be developed andcharacterized before they are deployed in thefield. A listing of state of the artinstrumentation suitable for deployment ateither surface sites or on airborne platforms isgiven in Appendix B. A key inadequacy ismeasurement of organic composition.Promising techniques have been identified, sothat it may be expected that new

instrumentation can be integrated into TAPField Campaigns on a relatively short timescale. There will be a strong linkage betweenInstrument Development and Characterizationinvestigators and the Field Studiesinvestigators to define the measurementneeds so that development activities directlymeet both the scientific and operational needsof the program.

In addition to aerosol properties, TAP FieldCampaigns will also require measurement ofvarious trace gas species that are aerosol

precursors (e.g., SO2, NH3, organics, etc.)and species that characterize thephotochemical milieu in which aerosoltransformations occur. It is anticipated that atleast one of the aircraft utilized in the programwill need to carry a full complement ofinstrumentation to characterize thephotochemical properties of the atmosphere inaddition to instrumentation for characterizingimportant aerosol properties. Other aircraft

involved in the program will need to beequipped with a subset of this instrumentation.The species that must be measured includephotochemical precursors such as NOx andhydrocarbons, intermediates such asaldehydes, and product species such as O

3,

H N O 3 and peroxides. Similar detailedmeasurements will need to be made on thesurface at the supersite and at least onesatellite site. Less detailed measurements,perhaps including only NOx, O3, CO, andhydrocarbons will need to be measured atother satellite sites. In many locationscontemplated for these Field programs, theneed for measurements at satellite sites canbe met with data from existing networksoperated by state and federal agencies.

The regional approach of TAP and the focus

on the life-cycle of ambient aerosol dictatesthat consideration be given to the differenttypes of mobile sampling platforms best suitedto accomplishing TAP’s mission. Mobilesampling platforms include large and smallaircraft, helicopters, airships, balloons, andtethered kitetoons. The focus of TAP onaerosols and their precursors from the surfaceto the tropopause over horizontal scales of200 km requires cross-disciplinary, multi-instrument aircraft payloads.

Field campaigns will require aircraft having

different sampling and measurementcharacteristics. For studies of aerosoltransformations in urban or power plantplumes, the use of a helicopter to determinesource characteristics is invaluable. Urbansource regions are only marginally accessibleby conventional aircraft owing to the usual airtraffic control restrictions, whereas helicopterscan easily fly in these regions using patternsand altitudes that enable good characterizationof the source region. Also, their lower cruisespeed allows spatially resolved measurementsto be made during traverses of compactplumes such as those from isolated powerplants. Helicopters were effectively usedduring the Summer 1995 Southern OxidantStudy Nashville Campaign to characterize theNashville urban source region and to conductstudies of power plant plume chemistry.

Studies of plume chemistry downwind andgeneral characterization of aerosol propertiesthroughout the project area will require a large



TAP Program Plan

34

aircraft fully equipped with the requiredcomplement of aerosol/photochemicalcharacterization instruments. Because of thelarge amount of instrumentation required on asingle platform, this aircraft will have to havesignificant payload capacity and be capable offairly long duration (4 to 6 hr) flights. Aircraftthat meet these requirements include the DOEGrumman Gulfstream G-1, the NOAA P-3, theNational Center for Atmospheric ResearchC130, the Canadian National ResearchCouncil Convair 580, or the University ofWashington Convair 580.

Campaigns will also require the use of anaircraft with the capability for remote sensingof aerosols to define, for example, the verticaland horizontal aerosol concentration fieldsemanating from a source, or to characterizethe concentration fields of aerosols within theproject domain. Because the flightrequirements for the remote sensing aircraftwill generally be different than the aircraft usedfor in-situ measurements, a separate aircraftwill be necessary. In several previous fieldprograms remote sensing aircraft have flownin stacked configuration with the in-situ aircraftnecessary to provide a context forinterpretation of the in situ measurements.The remote sensing aircraft could also beused for other optical measurements of

aerosol properties, and potentially for cloudphysics measurements. Potentially a numberof aircraft could fill this role including theConstrucciones Aeronauticas SA (CASA) 212operated under contract for remote sensing tothe NOAA Aeronomy laboratory, or theUniversity of Washington Convair 580.

Science SupportRequirements

Support necessary to conduct field campaignsas outlined in each Field Campaign SciencePlan will be provided by TAP Science Support.This effort will include preparation ofOperations Plan for a given campaign,consistent with Science Plan, that will allowthese questions to be addressed usingavailable technology and resources.

It is expected that TAP Science Support will beresponsible to provide and operate theplatforms and baseline measurement

instruments during Field Campaigns. Theplatforms will include three aircraft, one forsource sampling, one for comprehensivechemical and physical measurements and onefor remote sensing; the TAP supersite, and 3to 6 satellite sites. It is anticipated that theremote sensing aircraft and the helicopter willcome equipped with instrumentation requiredfor their respective tasks. TAP ScienceSupport will be responsible for measurementsthat utilize tested and established methods, asdistinguished from Principal Investigatorinstruments, which will be supported throughpeer-reviewed funding process. It is expectedthat Science Support will, at minimum, providequality assured measurements at the surfacesites and by aircraft of gas-phase speciessuch as SO2 , NO, NO2 , NOy, and CO;

accumulation-mode aerosol size distributions;filter collection and analysis for major aerosolcomponents; aerosol mass (surface only), andrelated quantities.

TAP Science Support will also be responsiblefor providing the basic meteorological data forthese studies. This will include meteorologicalsoundings (rawinsondes), a detaileddescription of wind fields and boundary layerheight (profiler network), and weatherforecasting and nowcasting to assist inCampaign Operations. Operation of chemical

transport models in real time and forecastmode will enable most effective deployment ofTAP resources, especially aircraft platforms.

TAP Science Support will also have majorresponsibility for obtaining external data duringField Campaigns and afterwards in theanalysis and interpretation of Campaigns. Animportant example is obtaining satellite data.Satellite observations can be used to definewidespread regional aerosols (Lyons, 1980).Such data will provide important context forTAP measurements and therefore need to be

made available in real time for planning andconduct of the field measurements.Quantitative aerosol retrievals are availablefrom a number of current satellite instruments,albeit with limitations due to frequency ofoverpass and interferences in measuredradiance (King et al., 1999). Considerablyimproved aerosol products will becomeavailable following launch of the NASA EarthObserving System AM platform, expected in

TAP Science

Support will

provide and

operate the

platforms and baseline

instruments

and make

meteorological

measurements

during Field

Campaigns.




35

Key areas of

instrument

development

include

measuremen

of aerosol

chemical

composition,

characterizing

aerosol

physical

properties,

and

integration of

physical and chemical

property

measurements

late 1999 (EOS, 1999). Next-generationsatellite products will be used for their uniquesynoptic viewpoint of aerosol column burden,and, in the near future, vertical structure bysatellite-borne Lidar.

The Science Support Team will also have theresponsibility to construct the deployablesupplemental facilities, locate and obtainsuitable sites, typically in conjunction with localair quality entities or educational institutions,provide communications, office space forparticipants, lab space as required and a user-friendly mechanism to allow ready accessibilityof data by all participants during campaignsand the resources to archive the data forsubsequent analysis. Other support functionsinclude QA/QC and data base maintenance.TAP management will assist PIs indisseminating scientific results by providing forpress releases, workshops, conferencesessions, and special issues of journals.

5.2 Instrument

Development and

Advanced

CharacterizationAtmospheric aerosols consist typically of anexternal mixture of particles that arethemselves composed of a multitude ofinternally mixed compounds. For TAPactivities to successfully quantify the chemicaland physical properties of ambient particles,this complexity must be recognized anddetermined. Improved understanding ofsource-receptor relationships and thepotentially harmful health effects of ambientparticles requires information on the size-

dependent aerosol chemical compositionMany of the compounds comprising aerosolparticles are volatile or semi-volatile (such asammonia, nitric acid, and organics), resultingin exchange with the gas phase while in theatmosphere as well as in artifacts in samplingand analysis. TAP field measurements willtherefore require reliable, calibrated, and wellcharacterized instruments to measure thephysical and chemical properties of ambient

particles and the air in which they areembedded. The Instrument Development andAdvanced Characterization (IDAC) componentof TAP will be closely linked with the fieldcomponent and participants in the instrumentdevelopment component will participate in thefield programs.

Traditionally, aerosol studies have focused onclassifying aerosols according to their size,number concentration, and bulk chemicalcomposit ion; relatively few detailedmeasurements of size-resolved compositionhave been made. A comprehensive suite ofmeasurement capabilities will be required toaddress the scientific questions of TAP. TableB.1 in Appendix B lists capabilities for in-situmeasurements of aerosol physical andchemical properties that are currently availableor are expected to be available at the outset ofTAP. The list is not intended to be exhaustive,however, it demonstrates that many differentmeasurement techniques must be integratedin order to obtain a more complete picture ofthe gas/particle equilibrium.

The key areas where development of newinstrumentation or refinement of existingmeasurement techniques is required toaddress the TAP research tasks includemeasurements of aerosol chemical

composition, characterizing aerosol physicalproperties, and integration of physical andchemical property measurements. Related tothese key areas, TAP should focus instrumentdevelopment on techniques for quantifying thecomposition of the organic fraction of ambientparticulate matter, measurements of the gas-phase species that form new particles, size-r e s o l v e d c h e m i c a l c o m p o s i t i o nmeasurements, and integration of physicaland chemical measurement techniques. Foreach of these areas, rapid-response aerosolmeasurement techniques may be required,

particularly for aircraft platforms and toobserve how certain physical and chemicalprocesses affect ambient particles.

Aerosol ChemicalComposition

The chemical composition of the atmosphericaerosol varies with particle size, geographicallocation, and time. Particles with the same



TAP Program Plan

36

diameter have also been shown to exhibitdifferent chemical compositions. Ultimately,determining which sources of aerosols mustbe regulated requires understanding of thevariation of chemical composition with particlesize from the sub-1 nm molecular scale to 10µm diameter coarse particles. Size-resolvedcomposition measurements can provideinformation on mechanisms of chemicaltransformation and on the contributions ofvarious species to particular aerosol effects.New instruments are required to improveunderstanding of atmospheric aerosolchemistry, particularly in quantifying the varietyof species that are present, observing thechemical evolution of the aerosol, andmeasuring aerosol formation processes.

Organics are virtually always present inatmospheric aerosols. They can comprise asignificant fraction of the total aerosol mass(often between 20 and 50%) and may play animportant role in new particle formation.Current state-of-the-art techniques arecapable of speciating only between 10% and20% of the organic fraction of the ambientaerosol. Understanding the organic aerosolfraction is thus a high priority.

A major effort is needed to develop real-timemethods to measure the polar organiccomponent of particulate matter, as these

compounds are expected to play an importantrole in determining the water uptake propertiesof organic containing particles. Thephotochemical evolution of the organic aerosolcan also be investigated by measuring thechanging degree of oxygenation of the organicaerosol. Useful measurements of this typeinclude: organic mass fractionated by polarity,measurements of functional groups associatedwith organic particulate matter, measurementof selected molecular-level tracers of primaryand secondary organic carbon, andmeasurements of water-soluble and water-insoluble organics. Continued development ofthese types of measurements would beextremely valuable.

The lack of closure between measured organicspecies and gravimetric mass, especially forsituations with a significant organic loading,could be due to an inaccurate value for theaverage molecular weight per carbon weight.Thus, measurements leading to a more

accurate assessment of this quantity arenecessary.

The above techniques for quantifying organicspecies present in the ambient aerosol mustbe capable of providing some particle size-

resolved information. Techniques should becapable of discriminating primary fromsecondary organic particulate matter andbetween anthropogenic and biogenic organiccarbon. Semi-volatile and water solubleorganics can be either desorbed or absorbedduring collection, and instrumentation thatminimizes these sampling effects is required.Instrumentation developed for aircraftplatforms must be as small and light aspossible to facilitate deployment.

Nitrogen containing aerosols, another major

component of ambient particulate matter, areknown to be an important contributor tosecondary aerosol loadings. Much of thismaterial is derived from the transformationprocesses involved in the oxidation of nitricoxide emissions from combustion sources andthe reaction of ammonia with acidic gases andaqueous aerosols. Measurement methods forammonia are needed with time resolutionsfrom seconds to minutes and detection levelsbetween 10 and 30 ppt. Organic nitrogencompounds are of concern due to theirabundance, potential toxicity, radiative

properties, and for acting as a sink and sourceof NO and nitrogen dioxide. These compoundshave received considerably less attention thanthe corresponding inorganic compounds, andinstrumentation to allow rapid and sensitivedetection of organo-nitrogen species isneeded for both ground and air-based fieldmeasurements.

Single particle analysis techniques arerequired to provide unique information on thesize-resolved chemical composition of theambient aerosol and the state of mixing of

aerosol constituents (internal vs. external);these properties can be used to identifysources and growth mechanisms of aerosols.Techniques that can be used to analyzeindividual particles can be divided into thosethat require later laboratory analysis ofsamples from the field and those that analyzeparticles in real-time. For example,transmission electron microscopy (TEM) canprovide unique information on the size, shape,

Single

particle

analysis is

required to

determine size-resolved

chemical

composition

of ambient

aerosols and

the state of

mixing of

aerosol constituents.




37

mixing state, and composition of individualparticles. Figure 5.5 shows examples of singleparticles of mixed composition of seasalt andsulfate and nitrate. These measurements canbe made with sufficiently high time resolutionto permit aircraft sampling, as a statisticallymeaningful number of particles can becollected in a short period of time. Theparticles are subsequently analyzed in thelaboratory. Major improvements in TEMinstrument design are nonetheless required,including automation of the measurementprocess, interfacing and comparing TEMmeasurements with other measurementtechniques, developing the capability tospeciate organics, and instrument calibration.

In contrast to the TEM technique, which is

performed “off-line”, time-of-flight massspectrometric (TOF-MS) techniques canprovide real-time information on trace speciespresent within individual particles. Examples ofthe complex spectra resulting from the TOF-MS analysis of three different particles areshown in Fig. 5.6. Measurements such asthese demonstrate that individual particles canconsist of internal mixtures of several differentchemical species. TOF-MS techniques are notcurrently capable of providing quantitative real-time information on mass concentrations, andimproved quantitative capability is an

important area of development for theseinstruments.

New single-particle techniques are required forspeciating the wide range of organiccompounds. Similarly, there is a need forsurface selective analysis capabilities toevaluate, for example, the role of the particlesurface chemical composition in determininghygroscopic properties. TOF-MS systems alsoneed to be made cheaper, smaller, and withhigher sampling efficiencies. Advanced dataprocessing methods are required for efficiently

analyzing and interpreting the large amountsof data that are generated.

The focus of TAP on the processes controllingthe life-cycle of the ambient aerosol requiresthat instrumentation be available to measurethe chemical evolution of particles andprecursor gases. Instrument packages arerequired that can distinguish and examineprimary particles, i.e., particles emitted directly

Figure 5.5. Examples of Transmission Electron

Microscopy (TEM) images of single aerosol

particles showing detail of compositional and sizeinformation that may be gained. Images a) and b)

show subhedral halite (NaCl) and euhedral sulfate

crystals. The particle in b is in the smallest size

range of seasalt crystals. The images in c show

halite particles in various stages of conversion to

sulfate and nitrate. Grain A is partly converted,

whereas C has been completely converted to

nitrate and grains B to sulfates. From Buseck and

Pósfai (1999).




39

Measurements

of gas-phase

precursors

such as

sulfuric acid,ammonia, and

organics are

critical to

improved

understanding

of new particle

formation

in the atmosphere.

There is an important

need for

instruments to

identify the

presence of

newly formed

particles and

to quantify therate of

formation and

growth of new

particles.

0.0 100

4.0 103

8.0 103

1.2 104

2 3 4 5 6 7 8 910 20

Particle Diameter, nm

242

227

226

224

223

220

Figure 5.7. Selected nanoparticle size

distributions measured far downwind of Macquarie

Island. The sequence of measurements with

increasing downwind distance is 242, 227, 226,

224, 223, and 220. The distributions show growth

of newly formed particles to larger sizes close tothe island and then depletion of nanoparticles with

increasing downwind distance. From Weber et al.

(1998).

approaches for measuring particle shape,density and refractive index that are suited forlaboratory-generated aerosols have beenreported, but uncertainties that arise from thecomplexities of physical and chemicalmorphologies of real atmospheric particles aretypically not well established.

A critical need that must be met to improvecurrent understanding of the processesleading to new particle formation ismeasurements of gas-phase precursors likesulfuric acid, ammonia, and organics.Measurements of these precursors, whenconducted simultaneously with both the pre-nucleation molecular cluster size distributionand the pre-existing aerosol size distribution,will allow the conditions leading to new particleformation to be defined. Furthermore, someknowledge of both the bulk and individualchemical composition of particles in the 3-4nm size range is needed so that relevant gas-phase precursors can be unambiguouslyassociated with newly formed particles.

There is an important need for instruments toidentify the presence of newly formed particlesand to quantify the rate of formation andgrowth of new particles. A recently developedtechnique involving pulse-height analysis iscapable of determining the size distribution of

recently formed particles in the size rangebetween 3 and 10 nm but requires refinementfor application in urban-influenced areas.Representative results from the fielddeployment of the pulse-height unit are shownin Fig. 5.7, where the growth of newly formedparticles is clearly evident.

The particle number size distribution is afundamental physical property required forunderstanding the evolution and gas/particlepartitioning of the ambient aerosol. In urbanareas, significant variability in the number size

distribution often occurs over time-scalesshorter than a few minutes. Furthermore, foraircraft platforms, size distr ibutionmeasurements are required over time-scalesof a few seconds.

Ambient particle size distributions are made uptypically of three or four modes. The chemicalcomposition of these different modes, andtherefore their hygroscopic properties, can

vary significantly. Therefore, measurements ofwater uptake are required at different sizesrepresentative of the different modes and atdifferent relative humidities between 10% and95%. For ground-based platforms, thesemeasurements are required at approximately30 minute time resolution, whereas for aircraftmeasurements a time resolution of one-to-five

minutes or less will be necessary.

Size-resolved water uptake measurementsmust be performed simultaneously with size-resolved particle chemical compositionmeasurements so that different compositionsand sources of particles can be related to theobserved hygroscopic properties. Techniquesthat can delineate the influences of particlesurface composition from bulk compositionaleffects are needed so that the role of gas-to-particle conversion processes can beseparated from the role that different sources

of directly emitted particles might play indetermining particle hygroscopicity.

Recently, particle surface characteristics andparticle morphology have been implicated asimportant factors in determining how particleand labile gas-phase species interact. Newmeasurement techniques are required toelucidate particle non-sphericity and relevantsurface characteristics so these properties




41

A hierarchy o

models is

needed to full

integrate gas-

phase and

condensed-

phase

processes,

including

cloud

processes,

with emission

and the controlling

meteorology.

example, pulse compression millimeter radarsare sensitive enough to measure cloudboundaries and gain great scientific powerwhen used in conjunction with lidar. Increaseddetection sensitivity and range/temporalresolution is required in future lidarinstruments. Co-located sonic radar systemscould provide important meteorological data toelucidate how boundary-layer processes suchas entrainment and cloud processing alteraerosol properties.

Finally it should be noted that fieldmeasurements of aerosols, as well as somelaboratory studies, require sampling inlets.The ideal inlet and sampling system efficientlytransports the sample without losses ormodification to the observing instrument or

instruments independent of the samplingplatform. However, state-of-the-art inlets arefar from ideal, particularly for aircraftapplications. Sampling uncertainties related tovolatilization or condensation of water vapor,organic vapors and others volatile species,flow distortion and related aspirationinefficiencies, and other particle lossmechanisms are often far larger than theuncertainties of the sampling instrumentsthemselves, and despite much work theseerrors remain poorly constrained. Theproblem of artifact particles due to droplet

shattering inside aerosol inlets during in-cloudand in-haze sampling must be resolved so thatthe influence of clouds and elevated relativehumidity environments on ambient aerosolproperties can be properly investigated.


It is expected that TAP principal investigatorswho part icipate in Instrumentat ionDevelopment and Advanced Characterization

activities will take part in TAP Field Campaignsby conducting measurements at the supersiteor on the research aircraft. In either case it willbe required that the TAP Science SupportTeam provide space, power, andcommunications resources. TAP ScienceSupport will ingest data into the TAP datasystem and facilitate exchange of databetween investigators and provide externaldata as required during Field Campaigns and

subsequent analysis and interpretation ofresults. TAP Science Support will provideappropriate archiving of data from IDACinvestigators.

5.3 ModelingImportant as measurements are tounderstanding tropospheric aerosols, merelymaking measurements and reporting them willnot achieve the objectives of TAP. Theportfolio of results need to be synthesized andintegrated. This generally is done with theassistance of complex mathematical modelsthat describe the air quality conditions as afunction of the forcing of meteorologicalproperties, emissions patterns, air chemistry

and deposition over the spatial and temporalregime of concern. Most air quality models ofthis kind have been focused heavily onconditions that represent the regulatorybounds for averaging and for outputsrepresenting ambient concentrations.However, considerable effort is needed tocreate a new hierarchy of models that fullyintegrate gas-phase and condensed-phaseprocesses, including accounting for cloudprocesses, with emissions and meteorologicalfeatures in the spatial regime to beinvestigated. Such models, which predict

ambient concentrations by representing theprocesses that take place between emissionand receptor are referred to as "sourcemodels" to distinguish them from modelswhich are based on empirical relationsbetween ambient concentrations andemissions, known as "receptor models"(Seigneur et al., 1999).

The new codes will require bookkeeping on avery large number of variables, and willdemand a computational scale similar to those

used in today’s climate models. The modelsthemselves can create outputs of a widerange of variables, and can be used toinvestigate phenomena over a variety of timeand spatial resolution that are important forunderstanding atmospheric processes. Themodels to be developed and adopted for TAPwill be flexible in their access to output andtheir use of input data even though their formmay be far more complex than current



TAP Program Plan

42

regulatory models. The aim of these models isto provide a means not only for analyzing,inter-comparing, and interpreting theexperimental results, but also ultimately forextending and qualifying models used for airquality management practices.

The modeling component of TAP takes itsdirection from the program's emphasis onobtaining a process level understanding of thelife cycle of tropospheric aerosols. A detaileddescription of particle nucleation and growth isbest obtained by studying these process inisolation. This requires a zero dimensional(box) model. However, in order to studyregional scale implications, the detailedprocess level description has to be combinedwith all of the complications of the 3

dimensional world, including flow fields,boundary conditions, emissions, and mixing ofair masses. This requires a regional scalechemistry - transport model. It is proposedthat TAP concentrate its efforts on 1)developing advanced zero dimensionaldescriptions of aerosol chemistry andmicrophysics leading to computer codes(modules) that can be exercised either aloneor within a regional transport model and 2)carrying out regional scale simulations usingthese modules incorporated in existingtransport codes. While recognizing the

desirability of having many independentapproaches to doing the transport calculation,it is also recognized that there are efficienciesin having a common framework. It is thereforeproposed that TAP make available acommunity transport model that can be usedby investigators to inter-compare aerosolmodules, explore the regional scaleconsequences of aerosol interactions, andanalyze field observations.

“Cubic meter” models

A detailed description of aerosol nucleationand growth involves the processes of gasphase chemistry, homogeneous andheterogeneous nucleation, transfer of materialbetween the gas and particulate phase, andparticle - particle interactions. Some of theseprocesses are described by kinetic relationswhereas others are best described in terms ofphase equilibria. Different methods are

The modeling

component of

TAP takes its

direction from

the program's emphasis on

obtaining a

process level

understanding

of the life

cycle of

tropospheric

aerosols.

employed by different investigators torepresent these processes, and evaluating thesituations that favor one or another methods isa matter of active research. For example,aerosol size distributions can be representedin models by discrete size bins, modes ofspecified or evolving mean radius and width,or moments of the size distribution. For manyproblems the governing kinetic rateexpressions and thermodynamic propertieshave not yet been quantified and in somecases have not been even identified.

The field, laboratory, and theoreticalcomponents of TAP are expected to providethe information needed to construct moreaccurate detailed models. For example, inorder to predict new particle nucleation rates

under the range of conditions expected in thefield programs, current theories will have to beextended to include ternary mixtures, organics,ion induced process, and the effects of near-cloud environments. Accurate descriptions ofaerosol growth processes will requirelaboratory studies on the thermodynamicproperties of complex mixtures (includingorganics), accommodation coefficients, andrate constants. Laboratory data is alsoneeded to address the possible effects ofaerosol mediated reactions on gas phasechemistry. Based on suggestive but limited

evidence, these reactions can constitute a sinkfor free radicals and a source of NOx andreactive Cl. Predictions of the radiative effectsof aerosols will require laboratory results and atheoretical framework for determining theoptical properties (including long waveinteractions) of organics, carbon containingand mixed particles.

Field investigations are needed to provide theambient conditions which control the chemicaland physical aerosol interactions and to testwhether models are representing processes

correctly. For some aspects of aerosolevolution, it is the absence of field data whichis the limiting factor in constructing anaccurate model. For example, thefundamental physical and chemical relationsdescribing in-cloud oxidation are knownmoderately well but there is difficulty inpredicting the end results on the atmosphere.Cloud chemistry data and aerosol size spectrabefore and after cloud processing are needed.




43

Box models will also be used in the analysis offield observations, in particular for describingthe rapid chemistry and microphysics that is ina near equilibrium with the observed mixture oflong lived species (the contents of a smallvolume of air, say a cubic meter). This type ofcalculation yields rate information that cannotbe obtained directly from observations, forexample the rate of new particle formation.This type of calculation also yields theconcentrations of transient species such asfree radicals and H2 S O 4 . Thus, theconcentration of H2SO 4 can be calculatedfrom a model that uses observed concentra-tions of trace gases to determine the oxidationrate of SO2 and the observed size distributionof aerosol particles to determine the surfaceloss rate of H2SO4. The model can be tested

in a “closure” experiment by comparingcalculated and measured values for H2SO4.

Box models can also be used to follow thetime evolution of an air parcel without thecomplications that occur in the real 3dimensional world. Such calculations might beused to study the changes in aerosolcomposition and size distribution in a plumethat is advected away from a source region.

The challenge facing TAP is not only toimprove the theoretical basis for describing

atmospheric aerosols, but also to arrive at acompact description that can be used inregional scale t ranspor t models.Operationally, this will require using detailedbox models to explore aspects of thechemistry and physics of aerosols; then, byway of systematic sensitivity calculations,construct an abbreviated description that canbe used to convert the detailed box model intoa module that is both accurate and capablepractical implementation within in a transportcode.

Regional- and larger-scaleModeling

Because the real atmosphere is three-dimensional, and because air parcels neverexist in complete isolation, it is necessary toembed the aerosol calculations within a largerscale transport model. This model should becapable of resolving the spatial distribution of

Because the

real

atmosphere is

three-

dimensional,and because

air parcels

never exist in

complete

isolation, it is

necessary to

embed the

aerosol calculations

within a large

scale

transport

model.

pollutants within the 200 by 200 km fieldobservation area. Regional calculations willyield process level information on chemicalpathways, yields, and rates; concentrationfields that can be compared with observations;and estimates of the imports into theexperimental region and the exports from theregion.

Transport models will be used to develop anexperimental plan in preparation for a fieldcampaign. It is particularly important todetermine whether an anticipated signal dueto a process under investigation has a largeenough amplitude to stand out over the noiseof all other confounding variables. After thefield experiment, transport models (and cubicmeter models) will be a major part of data

analysis. It is these requirements that lead toa modeling focus on the same scale as theexperimental arena. A very importantcomponent of the modeling activity must bethe characterization of the meteorologicalvariables that are responsible for aerosoltransport and the representation of thistransport in the model.

The geographic domain of the transport modelis expected to be larger than the 200 by 200km experimental arena, albeit with coarserresolution outside of the field observation

area. A larger domain decreases thedependence of model solutions on boundaryconditions and allows for the calculation oftransport to and from a regional size area thatwill at times be part of a similarly polluted airmass. A regional scale context is alsoimportant as that is the scale upon whichmany energy related policies are evaluated.Models developed under TAP will providepowerful tools for the regulatory and healtheffects communities to use for determiningsource - receptor relations, exploring theeffectiveness of various energy policies and

technologies in reducing PM 2.5 levels, and fordetermining exposure due to specific size andchemical components of the ambient aerosolmixture. The global change community willfind the TAP transport models useful inyielding a detailed description of near-sourceregions.

It is proposed that a community model bemade available for doing regional scale



TAP Program Plan

44

calculations. One possibility is EPA's Models-3/Community Multiscale Air Quality (CMAQ,2001), which provides a flexible framework forincorporating advanced modules describingaerosols and gas-aerosol interactions. It isanticipated that most of the modeldevelopment projects under TAP will bedirected at the smaller box model scale andwill yield products that can be used within thecommunity model, or alternatively within otherexisting transport codes. As part of thesupport for a community model, the TAPScience Support Team will provide the neededinput files such as wind fields and emissioninventories.

An important component of the developmentof highly sophisticated mathematical models is

an evaluation procedure. Protocols areneeded for evaluating the representation ofindividual processes within the models, fordetermining the ability of the models to predictquantities such as source-receptor relationswhich cannot be directly measured, and alsofor determining the overall ability of the modelsto predict concentration fields. The protocolsneeded for these different applications are byno means obvious and will have to bedetermined as part of the TAP research effort.Having a component of the evaluationprocedure that focuses on process

representation is motivated by the experiencesof the photochemical modeling community.They have found that a good comparisonbetween calculated and observedconcentrations can be fortuitous and does notnecessarily imply that the model has correctchemistry, a feature that could lead toerroneous predictions of the effects ofemission controls. Conversely a poorcomparison with observed concentrations maybe due to errors in emissions and/or windfields, and does not necessarily imply that thechemistry or physics of the model is incorrect.Process analysis will examine the changes inthe amount of substances in each model gridcell due to the various processes of concern--emissions, advection, diffusion, deposition,phase changes, photochemistry, coagulation,dissolut ion--and compare these tomeasurements and to physical-basedunderstanding. Process tests will include suchitems as closure experiments for OH, H2SO4,

and light scattering coefficient, σ s p;comparisons between observed andcalculated concentration ratios near sourceregions for testing emission inventories; use oftracers such as 14C to evaluate the calculatedcontributions to aerosol mass from biogeniccompounds; and using ratios of substance thatreact at different rates to test the oxidationchemistry.

Field programs have to be designed with thesetests in mind. These tests, however, do notcompletely take the place of an overallevaluation in which observed and calculatedconcentration fields are compared. There aremany ways in which to do such a comparisonand a task will be to arrive at a protocol that isrelatively robust with respect to the stochastic

components of the driving meteorologicalfields. Another task will be to conductcomparisons between different modelinggroups, perhaps involving a community modelrun with different versions of an aerosolmodule. These types of comparisons areoften an excellent way to evaluate thestrengths and weakness of variousapproaches.

Interaction between modelers and laboratoryand field investigators is envisioned as a two-way street in which the modelers providequestions that need to be addressed by thelaboratory and field measurements and themeasurements provide input and insight forthe modelers.

Large Scale Computation

Computational requirements for the transportmodel will be extremely large. The number ofcomputed variables will be larger than in aphotochemical model of comparablesophistication because of the need to resolve

the aerosol distribution by both size andcomposition. It may be necessary also toresolve the distribution into differentmorphology classes. Spatial resolutionrequirements are also stringent because of theneed to resolve features within the 200 by 200km experimental arena. Fast parallelcomputers will be needed. It is important thatTAP establish links with computational effortsbeing pursued in DOE.

Computational

requirements

for the

transport

model will be extremely

large. Fast

parallel

computers

will be

needed. It is

important that

TAP establish links with

computational

efforts being

pursued in

DOE.




45

Laboratory

and

theoretical

studies are

essential to understand

the processes

that control

the life cycle

of

tropospheric

aerosols.


TAP Science Support will be responsible foracquiring meteorological data and for

preparing meteorological fields for use bymodelers. TAP Science Support will acquiresatellite data; air quality data and emissioninventories and make these data available toTAP investigators and the broader scientificcommunity to facilitate process modeling andcomparison of models and observations. Thisactivity will make use of modern Internet andweb-based technologies to enhance collab-oration among TAP investigators at multipleinstitutions and hasten reaching TAP goals.

5.4 LaboratoryStudies and TheoryThis component of TAP is designed togenerate the fundamental chemical andphysical knowledge that is essential forunderstanding the processes (formation,transformation, and deposition) that control thelife cycle of tropospheric aerosol particles.Only with a fundamental understanding ofthese complex phenomena can the predictive

modeling tools that represent the final productof TAP be fully realized. This element will betightly coupled to the field, modeling andhealth community activities needs, deriving itsresearch subjects on the basis of public healthstudies and field observations, and generatingthe appropriate data to fulfill the most criticalmodeling needs.

Although field observations are the key todefining the state of a system, they areinherently limited in their ability to characterizeprocesses (e.g., identify specific reactions and

determine their rates). To develop theappropriate theoretical framework, to testhypotheses, and to produce the appropriateinputs for the models requires going beyondobservation into experimentation undercontrolled conditions. Experimental andtheoretical studies will aim to characterize thefundamental properties and processes thatcontrol the formation, growth, evaporation,chemistry, phase transformations, optical

properties and dry deposition of atmosphericaerosols.

Recent advances in single particle analysistechniques have shown that troposphericaerosols are composed of a mixture of a large

number of substances such as inorganic saltsand acids, soot, mineral dust, semi-volatileorganic compounds, transition metals andothers. Until very recently field observations ofaerosol compositions were incapable ofproviding information on the chemicalcomposition of individual particles therebydistinguishing between internally andexternally mixed aerosols. In contrastlaboratory studies have for the most partfocused on single component model aerosols.

It is crucial that experiments clearly define

their relevancy to the pressing need to predictatmospheric aerosol processes. As anexample, lab experimental conditions shouldspan realistic environmental conditions(temperature, partial pressure, relativehumidity, and particle sizes). Past researchhas shown that unrealistic environmentalconditions such as a high partial pressure of areactive component can place a system into adifferent and unrealistic physical regime. Thelaboratory and theory work sponsored by TAPwill focus on aerosol systems of sufficientcomplexity to address questions raised by thefield and modeling efforts.

The response of field instruments to thecomplex aerosols in the ambient atmosphereis far from understood. Required arelaboratory experiments to provide essential“calibration ” of the field instruments.Therefore proposed research projects thatfocus on the calibration of field instrumentsusing characterized aerosols within thecontrolled environment of a laboratory areneeded. Other examples of proposedresearch projects that would fall into thiscategory would be collaborations between alaboratory group and a field group toinvestigate a particular physical property suchas the real refractive index of plausible aerosolcompositions to explain observations made byan optical instrument in the field.

The following describe key research issuesthat need to be resolved to insure a successfulfulfillment of the goals of TAP.



TAP Program Plan

46

Areas of Research

New particle formation

Atmospheric aerosols can be formed directlyby primary emissions of particulate matter or

secondarily through gas-to-particle conversionprocesses through homogeneous nucleation.The freshly nucleated nanometer sizedparticles can eventually grow through thecondensation of gas-phase molecules andcoagulation with other existing aerosolparticles.

The importance of the nucleation process tothe overall atmospheric aerosol loading and itsdetailed mechanism remains one of the keyunknowns in atmospheric aerosol research.For example, the recent development of new

field instrumentation made it possible toquantify atmospheric nucleation events invarious locations and under a great number ofconditions. When these field observationswere compared with predictions from classicalnucleation theory (employing the commonlyassumed nucleation mechanism), adiscrepancy of many orders of magnitudeswas uncovered. The field data indicate that,except for in the very remote atmosphere, thetrue rate of new particle formation is muchhigher than that predicted by the prevailingbinary classical nucleation theory. Severalhypotheses have been suggested to explainthese observations most of which invoke aternary nucleation process, such as ammoniaor organic compounds added to the commonbinary system of water and sulfuric acid.

To complicate the issue, current nucleationtheory largely relies on bulk thermodynamicproperties to describe the chemical potential ofthe critical cluster that may range from severalto tens of molecules. It would highly desirableto develop molecular models that will make itpossible to predict the rates from first

principles. The theoretical approaches are ata promising state, but critically requirebenchmark experiments. Experimentalstudies of nucleation rates versusconcentration of condensing molecules in thegas-phase, where the contribution fromcontaminant species is eliminated, arerequired for multicomponent systems. Withsuch experimental studies and improvedhomogeneous nucleation theories, the task will

be to determine the atmospheric conditionsunder which homogeneous nucleationprocesses play a significant role in aerosolloading and the conditions under whichhomogeneous nucleation can be ignored.

Two important types of secondary aerosolsare sulfates and organic compounds. Fieldand modeling studies have shown a clearcorrelation between sulfate aerosol productionin the troposphere and the presence of volatilesulfur compounds, such as dimethyl sulfide(DMS) and sulfur dioxide (SO2), as well as thedirect precursors to aerosol formation such asH2SO 4. The mechanisms for formation oforganic aerosols are much more complicatedbecause of the complex mechanisms foroxidation of the volatile organic compounds(such as isoprene and terpenes) to form thesecondary products (aldehydes, ketones, andorganic acids) that can condense as aerosols.Laboratory and theoretical studies are neededto understand the mechanisms and kinetics ofthe gas-phase oxidation of volatile organic andinorganic species to form the gas-phaseprecursors to nucleation of new aerosolparticles. It is only recently that first principlescalculations of reaction rates andthermodynamics and intermolecular potentialshave become accurate enough to fill outregions of parameter space not filled by

experimental data.

In the real atmosphere nucleation and particlegrowth are always in competition. The relativerates of these two competing processes willdetermine the influence that nucleation impartson the size and chemical distributions as wellas the total mass loading of the aerosol.

The nucleation events described above tend toproduce a large number of freshly nucleatedparticles. There might be a secondmechanism that continuously produces a low-level number of particles.

Being able to represent particle formation inmodels is clearly central to any aerosolprogram. Only through carefulexperimentation can the various hypothesesbe tested. TAP will conduct laboratory andtheoretical studies directed towards measuringnucleation rates and elucidating themechanisms that lead to the observed rapidnucleation rates.

In the real

atmosphere

nucleation

and particle

growth are always in

competition.

Being able to

represent

particle

formation is

central to

understanding aerosol

evolution and

representing

it in models.




47

There is

currently no

theory that

can relate

molecular- scale

interactions to

bulk-scale

experimental

observations.

Aerosol condensation and growthkinetics

Rates of condensation and evaporation(volatilization) of gas species onto and from

aerosol surfaces are fundamental to mostaerosol microphysical processes. Currentexperimental and theoretical studies of theseprocesses have been limited to relativelysimple chemical systems, either pure water orstoichiometric inorganic systems (e.g. sulfatesand nitrates). In view of the chemicalcomplexity of atmospheric aerosols that isincreasingly apparent, laboratory studies ofgas uptake rates need to investigateappropriate mixtures of inorganic and organicspecies. The dependence of condensation/ evaporation processes on heterogeneity of

bulk and surface composition is largelyunknown. This will require the development ofmultiple experimental techniques that cangenerate and monitor the evolution of particleswith complex chemical composition.

In addition, there is currently no theory thatcan comprehensively relate molecular scaleinteractions to bulk scale experimentalobservations. Detailed understanding ofgas/surface interactions over the full range ofatmospheric particle size (≤5 nm to ≥1 µm) isrequired in order to accurately model aerosol

microphysics, both in interpreting atmosphericobservations and ultimately for predictingatmospheric aerosol processes.

A case in point is the ternary NH3 /H2SO4 /H2Osystem that which largely represents theaerosol nucleation/growth process inconventional aerosol models. Even for thisrelatively simple system, gas uptake rateshave not been measured over the full range ofcompositions. The direct and indirect effect ofother species such as organic compounds onaerosol nucleation and growth has not beeninvestigated. Gas uptake measurements needto be extended to a wide range of particleparameters, including variable temperature,chemical composition and size. The effects ofco-deposition of multiple species on surfaceproperties and gas/surface kinetics will becritical to understanding realistic complexsystems. Because of these dependencies, itis important for experimental and theoretical

studies to closely model the environmentalconditions observed in the field. For example,a growing ammonium nitrate particle mighthave a labile adsorbed monolayer of organicoils that controls its growth and evaporation.The growth of such an ammonium nitrateaerosol might depend strongly on the local mixof gas-phase semi-volatile organic oils, anddiffer greatly from a pure laboratory-synthesized ammonium nitrate aerosol.The TAP research program will derive theappropriate accommodation coefficients thatare necessary to describe this phase of aparticle’s life cycle, and will emphasize thecoupling of laboratory, theory and fieldprograms to develop the detailed frameworkfor model parameterizations of gas/particleinteractions in the atmosphere.

Relative humidity and phasetransformations

A large fraction of atmospheric aerosolscontain hygroscopic substances that interactstrongly with water vapor. Particle size,composition, optical properties and phase areall functions of the ambient relative humidity.The phase of the aerosol is important becausethe properties of wet and dry particles differsubstantially. As compared to dry particles,wet particles tend to be larger, have lowerrefractive indices in the visible, higherabsorption in the infrared, and have largerreaction probabilities for several importantchemical reactions. Their fate when inhaled isalso strongly dependent on theirhygroscopicity.

An aerosol composed of a single hygroscopicsubstance will undergo a sharp solid to liquidphase transformation when the relativehumidity reaches a character ist icdeliquescence point. Further increases in

relative humidity results in particle growth andthe formation of a dilute solution droplet. Atrelative humidity conditions slightly above100% the same particle can be activated toform cloud droplets. When the relativehumidity is then decreased the dropletreversibly shrinks in size, except that it doesnot transform back to the solid phase at thedeliquescence point but instead becomessupersaturated and ef f lorescence




49

Quantifying the effects of aerosols on gas-phase concentrations is an integral part ofTAP. TAP research projects will identify thekey heterogeneous reactions and quantifytheir effects both on the aerosol particlecharacter ist ics and the gas-phaseconcentrations of certain chemical species.

Optical properties of troposphericaerosols

Several of the most important effects oftropospheric aerosol particles, visibilityreduction and climate forcing, are directlyrelated to the ability of the particles to scatterand absorb solar radiation. In addition, amajority of aerosol field instrumentation and allremote sensing techniques rely on derivingaerosol physical parameters using known andassumed optical properties of atmosphericaerosols. To date the experimental datacovering the optical properties of complexaerosol particles is scarce and the theoreticalf ramework present ly employed forextrapolating these data to more complicatedcases has not been well tested. In conjunctionwith the field program the TAP will derive theoptical data that are required to invert fieldobservation into aerosol loading.

Organic species in atmosphericaerosol particles

The term organics refers broadly to the classof a large number of compounds composed ofcarbon, hydrogen, nitrogen, sulfur,phosphorus, and oxygen that may includesoot, aldehydes, ketones, organic acids andsurfactants. The very fact that they areclassified so broadly reflects current lack ofknowledge. Recent field data indicate thatthese compounds are ubiquitous to thesurfaces of aerosols, even those nominallyinorganic in bulk composition. Many of theorganics are derived from the degradationproducts of naturally emitted VOCs such asisoprene, while others are of anthropogenicorigin. The role of organics in the processesthat control the life cycle of troposphericaerosol particles and their effects on health,visibility, and climate, is a key topic that will be

The term

“organics”

refers broadly

to the class o

a large

number of

compounds

composed of

carbon,hydrogen,

nitrogen,

sulfur,

phosphorus,

and oxygen

that may

include soot,

aldehydes,

ketones,

organic acids

and

surfactants.

The very fact

that they are

classified so

broadly

reflects current lack o

knowledge.

addressed by the Laboratory and Theorycomponent of TAP.

There currently exists a lack of knowledgeconcerning the type and concentration oforganic compounds within tropospheric

aerosol particles. In order to assess the roleof organics on the life cycle of aerosols it iscritical that the experimental theoretical andfield program studies work closely togetherwith the field component in order to identifythe most important compounds forinvestigation.

Aerosol transport and depositionprocesses

The focus of the TAP mission is to

characterize tropospheric aerosols in relationto health hazards and visibility reductioncaused by urban pollution centers. Thespatial limits chosen are on the order of 200km from a source, which limit the aerosolprocesses investigated to those that occurwithin such a near field. While some particleswill be transported beyond these limits,several important aerosol loss processes willoccur within these limits and are important forunderstanding the spatial and temporalaerosol mass loading from pollution plumes.Two such important processes are drydeposition rates and the scavenging ofaerosol particles by larger cloud droplets. Anaspect of this research program will be thequantification of the rates of aerosol lossthrough these mechanisms.


1. Providing Standards andFacilitating Comparisons of Aerosol

Sources

In order to facilitate intercomparisons betweenlaboratory experiments, field instrumentcalibrations, and field observations it will beimportant to develop and characterizestandard aerosol generation methods that canbe used by experimentalists and fieldscientists.



TAP Program Plan

50

2. Providing Sources oftropospheric aerosols for labresearch

Methods for the collection of real ambienttropospheric aerosol particles from the field tobe transported back to the lab for experimentalmeasurements of their reactivity, growth,morphology, etc. will be pursued. These willallow both access to instrumentation that is notfield-portable, and will help bridge the gapbetween lab-created aerosols and real-worldcomplex ones.

3. Data Bases

TAP is inherently multi-investigator and multi-disciplinary in nature. Thus, it is important toprovide for the rapid and effectivecommunication of results between all elementsof the TAP team. The development of databases and other means for sharing results in

common formats will be an important attributeof TAP.

4. Facilitating Collaborative Use ofSpecialized Laboratory

Instrumentation and TheoreticalModels.

Progress in the study of complex materialsand processes characteristic of atmosphericaerosols will require substantial and ongoingadvances in experimental and theoreticalcapabilities. This will require a significantinvestment of TAP resources. To optimize theimpact of this investment, every effort will bemade by resource developers to share theseresources (through collaborations and othermeans) as widely as possible with other TAPresearchers. TAP Science Support resourceswill be crucial to facilitating this collaborativeeffort.



51

While

ultimately the

Science

Support

activities of TAP will

depend

on the

requirements

of the

Science

Team, many

of these activities

can be

reasonably

anticipated

for planning

purposes.

6. Science Support

ImplementationThe Science Support component of TAP isseen as crucial to maximizing the productivityof the TAP Science team and thereby helpingto achieve the objectives of TAP. Theresponsibilities of TAP Science Support aredelineated into the following components:

Support for Field Studies. S u p p o r tnecessary to conduct TAP Field

Campaigns. Campaign planning andlog is t i cs ; conduc t ing base l inemeasurements at TAP supersite andsatellite sites and on aircraft platforms,aircraft support and coordination, QA/QC.Maintaining a web-based campaignlogistics and data server.

Data system and archive. Incorporatemeasurements into data base/archive tofacilitate model development and testing.Make data available to TAP investigatorsand investigators from cooperating

agencies. Acquiring external data requiredby TAP invest igators, includingmeteorological and satellite data.

Support for modeling activities. Preparationof meteorological drivers and gridded datasets for comparisons; establishing andmaintaining community models supportingswap in/out of modules.

Facilitating scientific communicationamong TAP investigators and serving theneeds of the interagency aerosol research

community and the broader scientificcommunity. This activity will includemaintaining a data base of publications,organizing special sessions at conferences,special issues

While ultimately the Science Support activitiesof TAP will depend on the requirements of theScience Team, many of the required activitiescan be reasonably anticipated for planning

purposes. The activities outlined here arebased on past experience in large-scale FieldCampaigns conducted by DOE and otheragencies (NOAA, NASA, NSF), often involvingmulti-agency coordination.

6.1 Support for

Field StudiesSupport necessary to conduct TAP FieldCampaigns as outlined in each FieldCampaign Science Plan will be provided byTAP Science Support. This effort will includepreparation of an Operations Plan, providingthe aircraft- and ground-based platforms andbaseline measurements for each FieldCampaign, conducting baseline atmosphericchemical, physical, microphysical, andmeteorological measurements, and providing

the data to the Science Team investigatorsand to the TAP archive. TAP Science Supportwill also assist Science Team Investigatorssubsequent to the Campaign in analysis,interpretation, and modeling.

The Operations Plan for a given campaign,will provide for carrying out the measurementsspecified the Science Plan consistent withavailable technology and resources. Toachieve this, TAP will need to develop amanagement structure to accomplish thedetailed planning that is needed to conduct

the large scale Field Campaigns that areplanned for TAP, and to operate the requiredfacilities in the field. A proposed managementstructure is shown in Figure 6.1. Planningand implementation activities will be overseenby the Chief of Operations. Each function inFigure 1 will be accomplished by a team ofscientists, technicians, and other supportpersonnel. Examples of the tasks for each ofthese teams are given in Table 6.1.



TAP Program Plan

52

Figure 6.1 Organizational structure for TAP field support activities

The measurements to be made by TAPScience Support and the instruments to beemployed will be selected under the guidanceand direction of the TAP Field Investigators

Team. TAP Science Support will beresponsible to set up, and calibrate thebaseline instruments prior to the campaign,operate these instruments during thecampaign, and provide quality assured data tothe data archive upon completion of eachcampaign.

TAP Science Support will be responsible forthe baseline measurements at the surfacesites, and on at least one aircraft platform.Baseline measurements are defined as those

measurements that utilize tested andestablished techniques. The need forspecialized one of-a-kind principal investigatorinstruments is also recognized. These will be

funded either through the normal peer-reviewprocess, or by sub-contract. For the surfacesites, the measurements that TAP will beresponsible for are listed in Table 6.2 as arethe desired specialized measurements. TAPexpects to deploy one supersite and up to sixsatellite sites for each Field Campaign. Asindicated in Table 6.1 some of the baselineinstruments will be provided for all sites,whereas others will be provided only for thesupersite.



Science Support Implementation

53

Table 6.1. Tasks of the Science Support Teams for operation of TAP FieldCampaigns

Logistics Quality Assurance/

Quality Control

Aircraft coordination

Support facilities forparticipating scientists

Communications,computer networks

Meeting rooms

Laboratory space

Housing

Ground site infrastructure

Access agreements

Power

Communication

Trailer rental and siting

Erection of samplingtowers

Safety plan

QA/QC Plan

Management

Standard operatingprocedures for routinemonitoring

Audits

Performance

Special studies (e.g.,measurement inter-comparisons)

Assemble and install scientificequipment

Maintain and operate baselineaircraft instrumentation

Arrange aircraft logistics

Hangar, lab, office space

Interaction with FAA

Coordinate Flight Plans

Manage data

Aircraft QA

Ground Based Network Atmospheric Dynamics and Transport

Procure and prepareinstruments

Locate and set up sites

Operate instruments

Calibrate, maintain, inter-compare

Manage data

Identify and locate groundbased instruments

Profilers

Lidars

Sondes

Towers

Calibrate and maintaininstruments

Manage data

Provide Meteorologicalforecasting to support flightoperations

Daily briefings

Trajectories

High resolution models



TAP Program Plan

54

Table 6.2. Measurements to be deployed at TAP surface sites

Aerosol, physical Aerosol, chemical Trace gases

Total Mass

Coarse mode size distribution(2 – 10µm)

Accumulation mode sizedistribution (0.08 – 2 µm)

Aitken mode size distribution(0.02 – 0.08 µm)1

Nucleation mode sizedistribution(0.003-0.02 µm)

1,2

Aerosol absorption

Multi-wavelength lightscattering

Vertical and horizontaldistribution (lidar)1

Multi-wavelength OpticalThickness

Aerosol hygroscopicity1,2

Bulk composition- To includeEC, OC, principal inorganicanions and cations

Size distributed composition(impactor)

Single particle composition1,2

Trace metals1,2

NO, NO2, NO

y, SO

2, O

3, CO,

Hydrocarbons

H2O21, Aldehydes1, HNO3

1

OH1,2, HO21,2, H2SO4

1,2,NH3

1,2

Perfluorocarbon tracers

1. To be measured at the supersite only.

2. Principal Investigator instrument to be funded through a Science Team proposal or bysubcontract.

TAP Science Support will be responsible alsofor instrumenting and operating the principalaircraft used in the campaign. This could bethe DOE G-1 aircraft, or an alternate aircraft oflarger size and endurance, and it may varyfrom campaign to campaign. It is anticipatedthat the services of a remote sensing aircraft,and helicopter would be obtained by contract.

Such aircraft are typically equipment with theinstrument required for their respective tasks.Support is required to set up, and calibrate the

baseline instruments, to operate theseinstruments in the field, and to provide qualityassured data to an archive upon completion ofeach campaign. It is presumed that anyaircraft TAP will use will be equipped withinstruments to measure atmospheric stateparameters, altitude, position, winds, andturbulence. A projected set of instrumentation

that TAP Science Support will take theresponsibility for providing is shown in Table6.3




55

Table 6.3. Measurements to be deployed on in-situ aircraft measurementplatform.

Aerosol, physical Aerosol, chemical Trace gases

Accumulation mode sizedistribution (0.08 – 2 µm)

Aitken mode sizedistribution(0.02 – 0.08µm)

Nucleation mode sizedistribution (0.003-0.02µm)1

Aerosol absorption

Multi-wavelength light

scatteringAerosol optical depth1

Bulk composition- To includeEC, OC, principalinorganic anions andcations

Size distributed composition

Single particle composition1

NO, NO2, NOy, SO2, O3, CO,Hydrocarbons

H2O2, Aldehydes HNO3

OH1 , HO21, H2SO4

1, NH31

Perfluorocarbon tracers

1. Principal Investigator instrument to be funded through a Science Team proposal or bysubcontract.

Significant support staff and resources will berequired to maintain, deploy, operate thisequipment in the field. It is anticipated thatTAP Science Support will make use of existingcapabilities within the DOE complex whereavailable. Alternatively if a measurement isrequired and is otherwise not available, it willbe the responsibility of TAP Science Supportto acquire this capability by contract. A similarapproach may be taken for chemical analysesof filter samples.

TAP Science Support will also have theresponsibility of operating base linemeteorological instruments. This wouldinclude at least three wind profilers, and one ormore sites for the release of rawinsondes.

6.2 Data Systemand ArchiveThe TAP Data System and Archive activity is akey component of TAP Science Support. Thisactivity will include a data managementcomponent to support fieldwork and modelingactivities and to make TAP data available in a

form suitable for archiving. The datamanagement effort will be driven by thescientific needs of TAP. It will, as much aspossible, use either public domain orcommercial off-the shelf software and existinghardware and software resources. This datamanagement effort will take advantage of theexperience gained in other DOE efforts suchas ARM and EMSL. Archiving will becoordinated with other air quality archivingunder the auspices of NARSTO (NARSTO,2000).

TAP Data Management (TDM) will beresponsible for providing the communicationsinfrastructure during campaigns that isnecessary for communication among theparticipants and with the Internet. This support

will include providing mobile modems via acellular system and Internet service at thecentral command center.

Real-time satellite, radar and analysisproducts necessary for forecasting/nowcastingwill be provided. At the TAP command center,a multi-user computing facility will be providedfor use during debriefings for viewing datacollected by participants and for performing



TAP Program Plan

56

intercomparisons to aid in quality assuranceefforts. TDM will work with TAP scientists todetermine what auxiliary data will be neededto augment field measurements and willacquire these data. TDM will work with TAPscientists to specify the metadata that shouldbe acquired to understand the context of thefield measurements and will acquire thesedata. The TAP Web site will be used tocommunicate information about planned andon-going field campaigns.

TDM will work with TAP scientists to determinewhat data, in specified formats must beacquired to drive the TAP supported modelsand will provide these input data to TAPmodelers via the TAP web server.

TDM will provide the capability of running TAPsupported models via its web server. Themodeler will be able to choose the inputconditions, drive the model and examineintermediate and final products usingvisualization tools. By examining model runs atselected check points,‚ the modeler will beable to control and make changes to thecurrent model run.

The TAP Web Server will provide timelyinformation about the Program to the ScienceSupport staff, the Science Team, DOE

Headquarters and the general public. It will beused in the planning of campaigns, tocommunicate the status of ongoing campaignsand to distribute the data associated with thecampaigns.

As discussed above, the TAP Web Server willrun TAP supported models. It will also serveas the vehicle for advertising the contents ofthe TAP Data Archive and for data delivery.

The TAP data archive will serve as arepository for data and metadata collected in

campaigns, the input required to drive TAPsupported models and selected results ofmodel runs. Data will be made available instandard formats via a Web based interface(NARSTO, 2000). Users of TAP data will betracked so that they may be informed ofupdated versions of data they have received.

6.3 Support for

Modeling Activities

Modeling will be a major component of TAPand a major client of TAP Science Support. Itis intended that TAP Science Support facilitatethe development, use, and evaluation ofprocess models that represent atmosphericchemistry and aerosol microphysics. This canbe achieved by acquiring and making availableto TAP modelers (and external scientists)meteorological data sets suitable for drivingchemical transport and transformation modelssuch as forecast model output from the U. S.National Centers for Environmental Prediction(NCEP). These data serve as input to variousEulerian codes and can also be used to drivetrajectory models.

The Modeling Support activity will also providedata sets of chemical and microphysicalmeasurements that can be used for modelevaluation. In this effort it will be necessary toacquire and make available appropriateexternal data, such as from state and local airpollution agencies. Likewise ModelingSupport will provide gridded emissionsinventories for use by modelers.

All of the results from TAP measurementsmust be integrated into a useful data set thatcan be used interchangeably for verification ofmodels and interpretation of spatial andtemporal variations. Visualization and analysistools are required to examine this complexdata set and elucidate the effects of boundarylayer processes on the ambient aerosol. Indesigning new tools for observing particlechemical and physical properties and relevantmeteorological processes, attention must bepaid to how the data from each of the different

instruments will be integrated so that a clearpicture of the life cycle of ambient aerosols iscreated.

TAP

Modeling

Support will

make

available meteorological

data sets

suitable for

driving

chemical

transport and

transformation

models, thus facilitating

model

application

and

comparison.




57

TAP Science Support will

facilitate

novel

methods of

electronic

publication as

an effective

means of

disseminating

TAP results.

6.4 Scientific

Communication

TAP will be a broadly distributed activity, withresearch taking place in some dozens ofinstitutions. In such a situation there is atendency for progress to be slowed by lack ofready means of communication amongparticipants. To a great extent facilities forsuch communications exist, by email, filetransfer, and the web, but those tend to bebinary communications, or, in the case of theweb, one-way broadcasts without exchangeand feedback. It is intended in TAP tofacilitate multipartite communications not justduring Field Campaigns, but throughout theduration of the Program, to permit TAPinvestigators to engage in continuous scientificdialog. It is hoped that this approach willmaintain the excitement and engagement ofTAP researchers and lead to improved level ofinter-laboratory collaboration and more rapidprogress toward TAP objectives.

More traditionally TAP Science Support willmaintain an electronic archive and data baseof preprints and publications that will allow

TAP investigators and others to readilydownload TAP publications so that TAPfindings may be more readily and rapidlydisseminated, again advancing TAPobjectives. This is particularly important giventhe interagency interest in results of TAPresearch.

It is anticipated that increasingly scientificpublication will take place by electronicpublication, not just electronic images of staticpages, but, for example, animations of modeloutput and even executable models. TAPScience Support will endeavor to facilitatesuch novel methods of publication as aneffective means of disseminating TAP resultsand make TAP a model for such advancedpublication methods in atmospheric science.

Finally, TAP Science Support will assist indissemination of TAP results through regularScience Team meetings, by organizing specialsessions at national meetings of learnedsocieties, and by arranging special journalissues dedicated to TAP findings.



TAP Program Plan

60

thereby relieving TAP of the requirement toconduct these measurements and to translatethem into flow fields. The EMP and TAPprograms will be looking for opportunities tocollaborate, including conducting joint fieldmeasurement campaigns at a location such asSalt Lake City. As the Salt Lake City basinoften has a substantial aerosol loading, TAPmight make a substantial early advance to itsobjectives by joining forces with this project.

The Environmental Protection Agency hasestablished several "supersites" to characterizeparticulate matter, its constituents, precursors,co-pollutants, atmospheric transport, andsource categories in several urban regions:Atlanta, Baltimore, Fresno, Houston, LosAngeles, New York, Pittsburgh, and St. Louis(EPA, 2000). The enhanced measurementsat these sites would make these locations veryattractive for initial TAP studies of aerosolprocesses and evolution.

The Air Resources Board of the State ofCalifornia has been conducting a series ofstudies of particulate air pollution in CentralCalifornia (CARB, 2000). A TAP field study inconjunction with such a field study wouldgreatly benefit from the availability of keymeteorological and emissions data from stateand other agencies that would becomplementary to TAP investigations intoaerosol processes.

7.1. TAP Science

TeamThe Lead Scientist will be responsible foroverall scientific leadership of the program andfor representing the program within thescientific community. The Lead Scientist isexpected to make a major intellectualcontribution to the science conducted in theprogram, including analysis of findings andimplications, writing technical papers, andfostering the aims of the program to conductresearch that will achieve the objectives of theprogram, and to generate products that willmeet the requirements of the air qualityresearch and regulatory communities.

A key to the success of TAP will be its abilityto attract outstanding investigators from withinthe DOE National Laboratories, including

areas of these laboratories that have not beentraditionally supported by ESD programs; fromother Federal Agencies having expertise inatmospheric and aerosol science; and fromuniversities and the private sector. A furtherkey to success will be the substantialcommitment of effort that will be obtained fromthese individuals. Crucial to meeting theseobjectives will be the ability of TAP to providethe requisite level of funding that can attractoutstanding scientists at a high level ofcommitment. For this reason TAP willconcentrate its funding in a rather smallnumber of projects that are sufficiently wellfunded to meet these requirements.

As Field Studies are the centerpiece of TAP, itis crucial that TAP provide a structure for theeffective design, conduct, and interpretation of

Field Studies. The TAP approach to this willbe by means of Field Study Teams that willconstitute a major scientific commitment froma single institution or collaboration ofinstitutions. Members of these teams will beinvolved in developing and deployingspecialized measurements required for thecampaigns. The heads of these teams willcomprise the membership of the TAP FieldInvestigators Team that will have responsibilityfor major scientific direction, such as selectionof locations and schedules for TAP FieldCampaigns. It is anticipated that each of the

different teams will bring a different balance ofexpertise to the Science Team; for examplesome teams may bring greater expertise inparticle instrumentation, others in gas-phaseinstrumentation, others in meteorologicalmeasurements and their interpretation. Eachteam will be expected to make a contributionto the science of TAP, including majorpublications in key scientific journals. Theteam approach will benefit greatly from thecritical mass of effort that can be gained onlyfrom a major commitment of several seniorinvestigators, professionals, post-docs and

graduate students in a given institution orconsortium.

In addition to the Field Study Teams TAP willinclude several smaller science team projectsfocusing on a more narrowly defined effort,typically comprising the efforts of a singlesenior investigator and a post-doc and/orgraduate student(s). For modeling activitiesthis effort would be complemented by a



Deployment and Resources

61

programmer, for which additional fundingwould be required. Theoretical studies requiresomewhat lower funding, reflecting a lowerfractional effort by the senior investigator as istypical for such studies.

All science team projects will be awarded on

the basis of peer-reviewed proposals inresponse to DOE and/or joint agencyannouncements.

Estimated funding requirements for the firstthree years of the Program are given in Table7.1. During the start-up period of TAP thebudget will be ramped up over a three yearperiod. For the Field Study Teams this will beachieved by ramp up of the budgets of theseveral teams. Other projects will be initiatedby program announcements in each of the firstthree years of the Program. The latterapproach wil l al low target ing ofannouncements of opportunity to meet specificprogrammatic requirements as they becomeidentified.

7.2. TAP Science

Support TeamThe success of a program of the complexity ofTAP requires, in addition to the scientific

teams and single-investigator projects, asubstantial support endeavor. There arenumerous activities of science support that areidentified in Sections 5 and 6 as necessary forthis project. These activities are summarizedin Table 7.2 and given in detail in Tables 7.3and 7.4, along with anticipated budgetrequirements over the first three years of theproject. As discussed in Section 6, theScience Support Team will be populated fromgroups within the DOE National Labs andelsewhere having the necessary expertise tomeet the programmatic requirements.

7.3. TAP Project

SupportThe TAP Project Support activity (Table 7.5)will be responsible for management of TAPScience Support activities and for all fiscal andcontracting aspects of the Program, except for

The success

of a program

of the

complexity of

TAP requires,in addition to

the scientific

teams and

single-

investigator

projects, a

substantial

support endeavor.

science team funding which will beadministered directly by the DOE ProgramDirector.

7.4. Capital ItemsFor the Science Team components of TAP acapital allocation of 12.5% of operatingexpenses is indicated in Tables 7.1 and 7.2.

Capital requirements for Science Supportinstrumentation are given in Tables 7.6 - 7.8and summarized in Table 7.9. Theserequirements were evaluated based onexpected instrumentation requirements for thesupersite, the satellite sites, and the in-situmeasurement aircraft.

Capital funding in year will be 1 directed toacquisition of instrumentation for the supersiteand the in-situ measurement aircraft. Two keyinstruments will be acquired for each platform,a mobility aerosol analyzer for determiningparticle size spectrum over the two importantdecades, 0.01 to 1 µm, and a massspectrometric instrument that is capable ofmeasuring a broad spectrum of importantaerosol precursor gases. The full complementof TAP Science Support instrumentation forthe supersite will be acquired in year 1.Acquisition of certain aircraft instrumentation

will be deferred to years 2 and 3; this ispredicated on the availability of existinginstrumentation associated with the DOEResearch Aircraft Facility. Instrumentationwill be acquired for a single satellite site. Thiswill allow deployment of a satellite site in initialField Campaigns to evaluate the concept andallow for mid-course corrections.

In Year 2 two more satellite sites will bebrought on line. The important addition to theaircraft instrument suite will be threeintegrating nephelometers, which will allow the

relative humidity dependence of the lightscattering coefficient to be determined. Newparticle spectrometers will be acquired to takeadvantage of recent developments in the stateof such instruments.

In Year 3 the final three satellite sites will bebrought on line. Upgraded instruments forgas-phase measurements on the researchaircraft will also be acquired.



TAP Program Plan

62

Table 7.1 Overall Summary Budget

Program Element Year 1Budget

$K

Year 2Budget

$K

Year 3Budget

$K

TAP SCIENCE TEAM

National Laboratories 3930 7970 12000

Universities and Other Agencies 2840 5475 7850

TAP Science Team Subtotal 6780 13445 19850

TAP SCIENCE SUPPORT 3100 6475 9125

TAP PROJECT SUPPORT 900 900 900

TOTAL OPERATING 10780 20820 29875

Science Team Capital 850 1680 2480

Science Support Capital 1582 642 658

CAPITAL SUBTOTAL 2432 2322 3138

TOTAL OPERATING PLUS CAPITAL 13212 23142 33013



Schedule and Deployment

63

Table 7.2 TAP Science Team (TST) Budget

Year 1 Year 2 Steady State

Program Element

NumberofProjects

Budget$K NumberofProjects

Budget$K NumberofProjects

Budget$K

National Laboratories

Lead Scientist. 1 300 1 450 1 600

Field Study Teams 3 2000 3 4000 3 6000

Instrumentation Development andDeployment

2 500 3 750 4 1000

Modeling and Interpretation 1 500 2 1000

Laboratory Studies 2 800 4 1600 6 2400

Theory 1 330 2 670 3 1000

National Laboratories subtotal 3930 7970 12000

Universities, Other Agencies,

Private Sector

Major Field Teams 3 1000 3 2000 3 3000

Instrumentation Development andDeployment

2 500 3 750 4 1000

Modeling and Interpretation 2 450 3 925 4 1400

Laboratory Studies 3 750 6 1500 8 2000

Theory 1 150 2 300 3 450

Universities, Other Agencies,

Private Sector subtotal

2840 5475 7850

TAP SCIENCE TEAM TOTAL 6780 13445 19850

Capital for Science Team Projects 850 1680 2480

TAP SCIENCE TEAM TOTAL WITH CAPITAL 7630 0 15125 0 22330



TAP Program Plan

64

Table 7.3 TAP Science Support (TSS) Budget

Budget$K

Activity per Field Campaign Year 1 Year 2 SteadyState

Planning, Development, Implementation and Interpretation of Major FieldOperations

200 500 800

Supersite . Set up, calibrate TSS instruments prior to campaign. Identify site,negotiate occupancy, deploy trailers for TSS and TST instruments, establishpower and communications. Site set-up. Installation of PI instruments. OperateTSS instruments during campaigns, deliver preliminary data during campaign,Site break-down, conduct post-operation calibrations as necessary, deliver finaldata sets, work with TST as required on data interpretation.

500 1400 1800

Satellite sites (4-6). Set up, calibrate TSS instruments prior to campaign.Identify site, negotiate occupancy, deploy instruments, establish power andcommunications. Site set-up. Operate TSS instruments during campaigns, deliverpreliminary data during campaign, Site break-down, conduct post-operationcalibrations as necessary, deliver final data sets, work with TST as required ondata interpretation.

250 400 600

Meteorological Measurements. Deployment of surface, tower, tether balloonand remote sensing instruments including a network of three Radio AcousticSounding System (RASS) wind profilers. Operate instruments during campaigns,deliver data, work with TST in interpretation.

200 450 575

Aircraft operations: Fixed Wing Aircraft for in-situ measurements. Support

instrument installations, inlets, Ferry flights, flight hours during 6-week project,delivery of data to Data Assimilation Team. 6 weeks, average of one flight pertwo days, 5 hours per flight = 105 hours; @$5000 per hour

400 525 525

Aircraft operations: Helicopter for in-situ measurements. As above. 100 300 450

Aircraft operations: Fixed Wing Aircraft for remote sensing and cloudphysics measurements.

150 400 525

Instrumentation for airborne measurements: Acquisition, modification for TAPrequirements, modifications for flightworthiness, calibration, Operation duringcampaigns, delivery of preliminary data, De-install from aircraft, post operationcalibrations, deliver of final data sets, work with scientists on interpretation ofdata.

250 300 350

Lidar deployment (e.g., Micropulse Lidar), for continuous characterization ofvertical distribution of aerosol at supersite and three satellite sites: Operation,interpretation, providing data to science teams and working with them on use ofLidar data.

50 150 200

Meteorological support: Forecasting, nowcasting, hindcasting. Capturing, andanalyzing numerical analysis fields from weather forecast agencies, Execution ofmesoscale model such as MM5. Work with science teams in interpretation.

50 100 150

cont'd . . .




65

Table 7.3 TAP Science Support (TSS) Budget (cont'd)

Tracer deployment and analysis 150 250 500

QC and audits of instruments of TAP investigators. Liaison with QC officers ofcooperating entities to establish compatibility of data.

50 100 150

Chemical analysis of major ionic species, elemental and total organic carbon. 150 350 500

Molecular speciation of organics; Analytical costs for supersite only: 50samples @$5000

200 250 250

TAP Data Management (TDM) See Table 7.4 400 1000 1750

TOTAL 3100 6475 9125

Table 7.4 TAP Data Management (TDM) Budget

Budget$K

Activity Year 1 Year 2 SteadyState

Ingest Development @$25K 100 350 600

Level 1,2 product development @50K 100 100 100

Archive 100 300

External Data 50 100 100

Regional Meteorological Model Operations 50 100

Data distribution 100 200

Field Campaign support 125 100 100

Command Center setup 25 25

Field Q/A 25 25

Web server maintenance 25 25 100

Reports 25 100

TOTAL 400 1000 1750



TAP Program Plan

66

Table 7.5 TAP Project Support Budget

Budget$K

Activity Year 1 Year 2 SteadyState

Project Support Director 300 300 300

Fiscal Officer 200 200 200

Contracting 200 200 200

Public Relations and Outreach 100 100 100

Secretarial 100 100 100

TOTAL 900 900 900

Table 7.6 TSS Capital Requirements Super Site

Budget$K

Capital Item Year 1 Year 2 Year 3

SIMS (Secondary Ionization MassSpectrometer) for selected organics,HNO3, PAN

450

Mobility aerosol analyzer for aerosol sizedistribution 0.01 to 1 µm. 50

H2O2 50

NOx 50

SO2 6

O3 15

CO 15

TEOM (Tapered Element OscillatingMicrobalance)

10

Nephelometer 30

Aerosol absorption monitor 10

Data system 30

Pump and Manifold, includes filter housings 10

Shelter $5K each; four required 20

TOTAL 746 0 0




67

Table 7.7 TSS Capital Requirements Satellite Sites

Budget$K


Mobility aerosol analyzer for aerosol sizedistribution 0.01 to 1 µm.

50 100 150

NOx 10 20 30

SO2 6 12 18

O3 15 30 45

CO 15 30 45

TEOM 10 20 30

Nephelometer 30 60 90

Data system 10 20 30

Pump and Manifold, includes filter housings 10 20 30

Shelter 5 10 15

TOTAL 161 322 483



TAP Program Plan

68

Table 7.8 TSS Capital Requirements Aircraft Instruments

Budget$K


SIMS (Secondary Ionization MassSpectrometer) for selected organics,HNO3, PAN

450

Mobility aerosol analyzer for aerosol sizedistribution 0.01 to 1 µm

160

NOx 70

SO2 20

O3 25

CO 50

TEOM 10

H2O2 50

Nephelometers (3) w RH control 180

Particle Spectrometer 0.1-1 µm 70

Particle Spectrometer 0.3 - 30 µm 70

Filter sampling system 5

Miscellaneous, e.g., microscope slideexposure system.

10

TOTAL 675 320 175

Table 7.9 Total TSS Capital Requirements

Budget$K

Platform Year 1 Year 2 Year 3

Supersite 746

Satellite sites 161 322 483

Aircraft instrumentation 675 320 175

TOTAL 1582 642 658



69

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VTMX (Vertical Transport and Mixing Program,1998) Preliminary Science Plan for theEnvironmental Meteorology Program's VerticalTransport and Mixing Program. http://www.pnl.gov/ VTMX/sciplan.html.

Weber R. J., McMurry P. H., Mauldin L., Tanner D.J., Eisele F. L., Brechtel F. J., Kreidenweis S. M.,Kok G. L., Schillawski R. D., and Baumgardner D.(1998). A study of new particle formation andgrowth involving biogenic and trace gas speciesmeasured during ACE-1. J. Geophys. Res . 103,16385-16396.



73

Appendix A

Workshop ParticipantsAfter a draft version of this document had been circulated, a workshop was held at Brookhaven NationalLaboratory June 2-4,1999, to gain input from a broad community representing scientists from DOENational Laboratories, other federal laboratories, universities, and the private sector, and officials in thevarious federal agencies responsible for air quality and aerosol research. The following individualsparticipated in this workshop. * Denotes unable to attend in person but provided feedback on the draftreport.

Dr. Daniel Albritton*Director, NOAA Aeronomy LaboratoryMail Stop R/E/AL6

325 BroadwayBoulder, CO 80303-3328TEL: (303) 497-5785FAX: (303) 497-5340E-mail: [email protected]

W. Richard BarchetPacific Northwest National LaboratoryMSIN K9-30P.O. Box 999Richland, WA 99352TEL: (509) 372-6158FAX: (509) 372-6168E-mail: [email protected]

Robert A. BariBrookhaven National LaboratoryDepartment of Advanced TechnologyBuilding 197CP.O. Box 5000Upton, NY 11973-5000TEL: (516) 344-2629FAX: (516) 344-5266E-mail: [email protected]

Stephan E. BarlowPacific Northwest National Laboratory3335 Q Avenue, K8-88Richland, WA 99352TEL: (509) 376-9051FAX: (509) 376-0846E-mail: [email protected]

Tim BatesNOAA/PMEL7600 Sand Point Way NESeattle, WA 98115TEL: (206) 526-6248FAX: (206) 526-6744E-mail: [email protected]

Carmen M. BenkovitzBrookhaven National LaboratoryDAS/Environmental Chemistry Division

Building 815EP.O. Box 5000Upton, NY 11973-5000TEL: (516) 344-4135FAX: (516) 344-2887E-mail: [email protected]

Francis S. BinkowskiAtmospheric Sciences Division (NOAA)Mail Drop 80Research Triangle Park, NC 27711TEL: (919) 541-2460FAX: (919) 541-1379E-mail: [email protected]

Fredrick J. BrechtelBrookhaven National Laboratory

DAS/Environmental Chemistry DivisionBuilding 815EP.O. Box 5000Upton, NY 11973-5000TEL: (516) 344-6198FAX: (516) 344-2887E-mail: [email protected]

Peter R. BuseckDepartment of GeologyArizona State UniversityBox 871404Tempe, AZ 85287-1404TEL: (480) 965-3945FAX: (480) 965-8102E-mail: [email protected]

Gregory R. Carmichael204 IATLUniversity of IowaIowa City, Iowa 52240TEL: (319) 335-3333FAX: (319) 335-3337E-mail: [email protected]

Steven D. ColsonPacific Northwest National Laboratory3335 Q Avenue, K8-88

Richland, WA 99352TEL: (509) 376-4598FAX: (509) 376-0846E-mail: [email protected]

James CowinPacific Northwest National LaboratoryMailstop K8-88Box 999Richland, WA 99352TEL: (509) 376-6330FAX: (509) 376-6066E-mail: [email protected]

Robert J. CurranRadiation Science ProgramEarth Science Enterprise, Research

DivisionNASA Headquarters, Code YS300 E Street, SWWashington, DC 20546TEL: (202) 358-1432FAX: (202) 358-2770E-mail: [email protected]

Donald DabdubDepartment of Mechanical EngineeringUniversity of California, IrvineIrvine, CA 92697TEL: (949) 824-6126FAX: (929) 824-8585E-mail: [email protected]

Peter H. Daum

Brookhaven National LaboratoryDAS/Environmental Chemistry DivisionBuilding 815EP.O. Box 5000Upton, NY 11973-5000TEL: (516) 344-7283FAX: (516) 344-2887E-mail: [email protected]



TAP Program Plan

74

James W. DavenportBrookhaven National LaboratoryDepartment of Applied ScienceBuilding 179AP.O. Box 5000Upton, NY 11973-5000TEL: (516) 344-3789FAX: (516) 344-4334E-mail: [email protected]

J. Christopher DoranPacific Northwest National LaboratoryP.O. Box 999MSIN K9-30Richland, WA 99352TEL: (509) 372-6149FAX: (509) 372-6168E-mail: [email protected]

Sylvia A. EdgertonPacific Northwest National LaboratoryBattelle Washington Operations901 D St. SW, Suite 900Washington, DC 20024-2115TEL: (202) 646-5236

FAX: (202) 646-7845E-mail: [email protected]

Fred EiseleNational Center for Atmospheric

ResearchP.O. Box 3000Boulder, CO 80307TEL: (303) 497-1483FAX: (303) 497-1492E-mail: [email protected]

Thomas J. Feeley III*U.S. Department of EnergyFederal Energy Technology Center

(FETC-PGH)626 Cochrans Mill Road

Pittsburgh, PA 15236-0940TEL: (412) 892-6134E-Mail: [email protected]

Dr. Fred Fehsenfeld*NOAA Aeronomy LaboratoryMail Stop R/E/AL7325 BroadwayBoulder, CO 80303-3328TEL: (303) 497-5819FAX: (303) 497-5126E-mail: [email protected]

Jeffrey S. GaffneyBldg. 203/ER9700 South Cass Ave.Argonne National LaboratoryArgonne, IL 60439TEL: (630) 252-5178FAX: (630) 252-7415E-mail: [email protected]

Michael GurevichU.S. Department of EnergyForrestal BuildingMail Stop 6A-116Room 5G-086Washington, DC 20585TEL: (202) 586-6104FAX:E-mail: [email protected]

Jake HalesEnvair60 Eagle ReachPasco, WA 99301TEL: (509) 546-9542FAX: (509) 546-9522E-mail: [email protected]

D. Alan HansenEPRI3412 Hillview AvenueP.O. Box 10412Palo Alto, CA 94303TEL: (650) 855-2738FAX: (650) 855-2950

E-mail: [email protected]

Arthur M. Hartstein*U.S. Department of Energy19901 Germantown RoadGermantown, MD 20874-1290TEL: (301) 903-2760FAX: (301) 903-9482E-mail: [email protected]

George HidyUniversity of Alabama at BirminghamDept. of Civil and Environmental

Engineering1150 10th Ave. S. - BEC257Birmingham, AL 35294TEL: (205) 934-8499


Rudolf B. Husar*Center of Air Pollution Impact and Trend

AnalysisWashington UniversitySt. Louis, MO, 63130TEL: (314) 935-6099FAX: (314) 935-6145E-mail: [email protected]

Dan G. ImreBrookhaven National LaboratoryDAS/Environmental Chemistry DivisionBuilding 815E

P.O. Box 5000Upton, NY 11973-5000TEL: (516) 344-4493FAX: (516) 344-2887E-mail: [email protected]

Jack Kaye*Office of Mission to Planet EarthMail Code YSNASA Headquarters, Room 5R31300 E. St., S.W.Washington, DC 20546TEL: (202) 358-0757FAX: (202) 358-2770E-mail: [email protected]

Lawrence I. KleinmanBrookhaven National LaboratoryDAS/Environmental Chemistry DivisionBuilding 815EP.O. Box 5000Upton, NY 11973-5000TEL: (516) 344-3796FAX: (516) 344-2887E-mail: [email protected]

Douglas R. LawsonNational Renewable Energy Laboratory1617 Cole BoulevardGoldon, CO 80401TEL: (303) 275-4429


Richard LeaitchARMPAtmospheric Environment Service4905 Dufferin StreetDownsview, Ontario M3H 5T4CANADATEL: (416) 739-4616FAX: (416) 739-4211E-mail: [email protected]

Yin-Nan LeeBrookhaven National LaboratoryDAS/Environmental Chemistry DivisionBuilding 815E

P.O. Box 5000Upton, NY 11973-5000TEL: (516) 344-3294FAX: (516) 344-2887E-mail: [email protected]

Joel Levy*Office of Global ProgramsNational Oceanic and Atmospheric

Admin.1100 Wayne Ave., Suite 1210Silver Spring, MD 20910-5603TEL: (301) 427-2089 x 21FAX: (301) 427-2073E-mail: [email protected]

Melissa M. LundenLawrence Berkeley National LaboratoryEnvironmental Energy Technology1 Cyclotron RoadMail Stop 29C-102Berkeley, CA 94720TEL: (510) 486-4891FAX: (510) 486-7303E-mail: [email protected]



Workshop Participants

75

Peter W. LunnEnvironmental Sciences Division, SC-74Office of Biological and Environmental

ResearchOffice of ScienceU. S. Department of EnergyGermantown, MD 20874TEL: (301) 903-4819FAX: (301) 903-8519

E-mail: [email protected]

Sasha MadronichNational Center for Atmospheric

ResearchP.O. Box 3000Boulder, CO 80307TEL: (303) 497-1430FAX: (303) 497-1400E-mail: [email protected]

Karen L. MaglianoCalifornia Air Resources BoardP.O. Box 28152020 L StreetSacramento, CA 95812

TEL: (916) 322-7137FAX: (916) 327-8524E-mail: [email protected]

Scot T. MartinDept. of Environmental Sciences and

EngineeringCB #7400, 112 Rosenau HallUniversity of North CarolinaChapel Hill, NC 27599-7400TEL: (919) 966-9698FAX: (919) 966-7911E-mail: [email protected]

Robert L. McGrawBrookhaven National LaboratoryDAS/Environmental Chemistry Division

Building 815EP.O. Box 5000Upton, NY 11973-5000TEL: (516) 344-3086FAX: (516) 344-2887E-mail: [email protected]

Peter H. McMurryUniversity of Minnesota125 Mechanical Engineering111 Church St., SEMinneapolis, MN 55455TEL: (612) 624-2817FAX: (612) 626-1854E-mail: [email protected]

Dr. James F. Meagher*Director, NOAA Aeronomy LaboratoryMail Stop R/E/AL6325 BroadwayBoulder, CO 80303-3328TEL: (303) 497-3605FAX: (303) 497-5126E-mail: [email protected]

Edwin L. MeyerU.S. Environmental Protection AgencyOffice of Air Quality Planning &

StandardsMail Drop 14Research Triangle Park, NC 27711TEL: (919) 541-5594FAX: (919) 541-0044E-mail: [email protected]

Leonard NewmanBrookhaven National LaboratoryDAS/Environmental Chemistry DivisionBuilding 815EP.O. Box 5000Upton, NY 11973-5000TEL: (516) 344-4467FAX: (516) 344-2887E-mail: [email protected]

Linda J. NunnermackerBrookhaven National LaboratoryDAS/Environmental Chemistry DivisionBuilding 815EP.O. Box 5000

Upton, NY 11973-5000TEL: (516) 344-5567FAX: (516) 344-2887E-mail: [email protected]

Peter PaulBrookhaven National LaboratoryDirector's OfficeBuilding 460P.O. Box 5000Upton, NY 11973-5000TEL: (516) 344-8623FAX: (516) 344-5803E-mail: [email protected]

William T. PennellPacific Northwest National Laboratory

P.O. Box 999MSIN: K9-34Richland, WA 99352TEL: (509) 372-6256FAX: (509) 372-6153E-mail: [email protected]

Joseph M. Prospero*RSMAS/MACUniversity of Miami4600 Rickenbacker CausewayMiami, FL 33149TEL: (305) 361-4789FAX: (305) 361-4891E-mail: [email protected]

Lawrence F. Radke

National Center for AtmosphericResearchP.O. Box 3000Boulder, CO 80307TEL: (303) 497-8778FAX: (303) 497-8770E-mail: [email protected]

Catherine H. ReheisWestern States Petroleum Association1115 11th StreetSuite 150Sacramento, CA 95814TEL: (916) 498-7752FAX: (916) 444-8997E-mail: [email protected]

Philip B. RussellMS 245-5NASA Ames Research CenterMoffett Field, CA 94035-1000TEL: (650) 604-5404FAX: (650) 604-6779E-mail: [email protected]

Eric S. SaltzmanAtmospheric Chemistry ProgramNational Science Foundation4201 Wilson Blvd./Room 775Arlington, VA 22230TEL: (703) 306-1522FAX: (703) 306-0377E-mail: [email protected]

Stephen E. SchwartzBrookhaven National LaboratoryDAS/Environmental Chemistry DivisionBuilding 815EP.O. Box 5000Upton, NY 11973-5000TEL: (516) 344-3100FAX: (516) 344-2887E-mail: [email protected]

Arthur J. SedlacekBrookhaven National LaboratoryDepartment of Advanced TechnologyBuilding 703P.O. Box 5000Upton, NY 11973-5000


John H. SeinfeldDivision of Engineering & Applied

ScienceMail Code 104-44California Institute of TechnologyPasadena, CA 91125TEL: (626) 395-4100FAX: (626) 585-1729E-mail: [email protected]

David StampfBrookhaven National LaboratoryInformation Technology Division

Building 515P.O. Box 5000Upton, NY 11973-5000TEL: (516) 344-4148FAX: (516) 344-3211E-mail: [email protected]



TAP Program Plan

76

Roger Tanner*Tennessee Valley Authority201 CEBMuscle Shoals, AL 35660TEL: (256) 386-2958FAX: (256) 386-2499E-mail: [email protected]

Joyce L. TichlerBrookhaven National LaboratoryDAS/Scientific Information Systems

GroupBuilding 490DP.O. Box 5000Upton, NY 11973-5000TEL: (516) 344-3801FAX: (516) 344-3911E-mail: [email protected]

Margaret A. TolbertCIRESCampus Box 216University of ColoradoBoulder, CO 80309-0216TEL: (303) 492-3179FAX: (303) 492-1149E-mail: [email protected]

Owen B. ToonCampus Box 392LASPUniversity of ColoradoBoulder, CO 80309-0392TEL: (303) 492-1534FAX: (303) 492-6946E-mail: [email protected]

Barbara TurpinDept. of Environmental SciencesRutgers University14 College Farm RoadNew Brunswick, NJ 08901


James S. VickeryU.S. Environmental Protection AgencyMD-75Research Triangle Park, NC 27711TEL: (919) 541-2184FAX:E-mail: [email protected]

Richard WagenerBrookhaven National LaboratoryDAS/Scientific Information Systems

GroupBuilding 490DP.O. Box 5000Upton, NY 11973-5000TEL: (516) 344-5886FAX: (516) 344-3911E-mail: [email protected]

John G. WatsonDesert Research Institute2215 Raggio ParkwayReno, NV 89512TEL: (775) 677-3166FAX: (775) 677-3157E-mail: [email protected]

Marvin L. WeselyBuilding 203, ERArgonne National LaboratoryArgonne, IL 60439TEL: (630) 252-5827FAX: (630) 252-5498E-mail: [email protected]

Anthony S. WexlerMechanical EngineeringUniversity of DelawareNewark, DE 19716-3140TEL: (302) 831-8743FAX: (302) 831-3619E-mail: [email protected]

Creighton D. WirickBrookhaven National LaboratoryDepartment of Applied ScienceBuilding 179AP.O. Box 5000Upton, NY 11973-5000TEL: (516) 344-3063FAX: (516) 344-4130E-mail: [email protected]

Douglas R. WorsnopCenter for Aerosol and Cloud ChemistryAerodyne Research, Inc.45 Manning RoadBillerica, MA 01821TEL: (978) 663-9500, x225FAX: (978) 663-4918E-mail: [email protected]

Douglas WrightBrookhaven National LaboratoryDAS/Environmental Chemistry DivisionBuilding 815EP.O. Box 5000Upton, NY 11973-5000TEL: (516) 344-2687FAX: (516) 344-2887E-mail: [email protected]



77

Appendix B

Instrumentation and CharacterizationTechniques Available for Use in TAPInstrumentation and measurement techniques that are examples of the state of the art that may beapplied in TAP field programs are presented here. Table B1 presents techniques for measurement andcharacterization of aerosol and single particle size distributions, composition, and other properties.Instrumentation and techniques suitable for characterizing gas-phase species are listed in Table B2.Table B3 lists instrumentation and techniques for characterizing pertinent meteorological variables. TheTables also indicate the suitability of the techniques for use on airborne platforms, the temporal resolutionand, for aircraft deployment, the approximate corresponding spatial resolution.

Table B1. Techniques for Characterization of Aerosol Composition and Properties

Measurement Measurand Technique TimeResolution

AirbornePlatform

SpatialResolution

SIZE DISTRIBUTION

SizeDistribution/ParticleFormation &Growth

Size and Conc3-10 nm

Pulse Height Analysis 1-60 sec + 100 m –

6 km

Size and Conc

3-150 nm

Mobility Analysis -

Nano DifferentialMobility Analyzer (DMA)

60 s -

15 min

+ 6 km +

9 km

Size and Conc

3-150 nm

Multiple CondensationParticle Counters atDifferentSupersaturations

1-60 sec + 100 m -6 km

Size Distribution Size and Conc10-1000 nm

Mobility Analysis -Long DMA

30 s -15 min

+ 6 km +9 km

Size and Conc1000-2500 nm

Aerodynamic ParticleSizer

5 - 15 min 9 km

Haze and Aerosol

Size Distribution

Size and Conc

100-3000 nm

Passive Cavity Aerosol

Spectrometer Probe(PCASP)

1-60 sec + 100 m –

6 km

Cloud and AerosolSize Distribution

Size and Conc1-50 µm

Forward ScatteringSpectrometer Probe(FSSP)

1-60 sec + 100 m –6 km

Cont'd...



TAP Program Plan

78

Table B1. Techniques for Characterization of Aerosol Composition and Properties, Cont'd.


AirbornePlatform

SpatialResolution

NUMBER, MASS CONCENTRATION

Total NumberConcentration Conc >3, >10 nm Ultrafine CondensationParticle Counter(UCPC), CondensationParticle Counter (CPC)

1 - 60 s + 100 m6 km

Total Particle Mass Mass< 1 µm,< 2.5 µm,< 10 µm

Tapered ElementOscillating Microbalance(TEOM)

Mass< 1 µm,< 2.5 µm,< 10 µm

Filter collection; humiditycontrolled weighing

8 h

CHEMICAL SPECIATION

Size DistributedChemicalComposition

Anions & Cations50-10000 nm

Micro-Orifice-Multi-Stage Impactor(MOUDI)

3 hrpolluted; 8-24 hr clean

100-1000 km

Organiccompounds50-10000 nm

Micro-Orifice-Multi-Stage Impactor(MOUDI)

3-24 hr 100-1000 km

Bulk OrganicAerosolComposition

Polar, Non-polarorganics,carboxylic acids,'major' species

Gas ChromatographyMass Spectrometry(GC/MS)

3 hr

Single ParticleMolecular

Composition

ElementalComposition

10 nm -1000 nm;possibly size

Time of flight SingleParticle Mass

Spectrometry (TOF/MS)

> 5 min +

Single ParticleElectronMicroscopy

Size dependentelementalcomposition downto Carbon -possibly carbon

Transmission electronmicroscopy

1-10 min + 6-60 km

Semi-ContinuousBulk ChemicalComposition

Particle sulfate andnitrate

Flash vaporization 5-10 min

Semi-ContinuousWater Soluble

ChemicalComposition

Total mass ofmajor anions and

cations for particles

Condensation followedby impaction and

collection for IonChromatography

5-10 min

OPTICAL PROPERTIES

Particle LightScattering,

Light scatteringcoefficient for dryparticles, one ormore wavelengths

Integratingnephelometer

1 s + 100 m

Cont'd...



Instrumentation and Characterization Techniques

79



AirbornePlatform

SpatialResolution

OPTICAL PROPERTIES (cont'd)

Particle LightScattering atElevated RelativeHumidity

Light scatteringcoefficient forparticles as f(RH)

RH controlled integratingnephelometer

+

Particle Sphericity/ Index of Refraction

Light scattering asa function ofangular positionabout levitatedparticle

Integrating SphericalScattering Device

?

Particle LightAbsorption

absorptioncoefficient~550 nm

Aetholometer 1 min +

Particle Soot AbsorptionPhotometer (PSAP)

1 min +

Photo-acousticabsorption

+

HUMIDITY RESPONSE AND ACTIVATION

Particle WaterUptake - functionof RelativeHumidity

Droplet growth at20%, 40%, 60%,80%, 95% RH for 4Dp's over ambientsubmicrometer sizedistribution

Hygroscopic TandemDifferential MobilityAnalyzer (HTDMA)

SeveralHours

+ (?)

CloudCondensationNuclei (CCN)Spectrum

Concentration ofcloud droplets asfunction ofsupersaturation

Continuous flow CCNCounter

+

Concentration ofcloud droplets asfunction ofsupersaturation

Thermal GradientDiffusion Chamber

REMOTE SENSING

Aerosol ColumnBurden

Light extinction Sun Photometry

Vertical Profile ofParticle Loading

Relative orabsolute particleextinction vs.height

Lidar: Depolarization,Backscatter, Raman,and differentialabsorption (up/downlooking)

+

Relative orabsolute particleextinction vs.height

Satellite (PICASSO-CENA in 2000)

Cont'd...



TAP Program Plan

80



AirbornePlatform

SpatialResolution

REMOTE SENSING (cont'd)

Cloudmicrophysicalproperties

Radar formicrophysicalproperties of clouds

Ground based; Satellite(NASA Cloudsat in2003)

+

Vertical Profile ofParticle SizeDistribution, Lightscatter coefficient

Variation of numberconcentration withparticle size withaltitude

Tethered/Free-floatingBalloons with aerosoloptical probes




81

Table B2. Techniques for Characterization of Gas-Phase Species

Measurand Technique TimeResolution

AirbornePlatform

SpatialResolution

Hydroxyl radical(OH)

Laser InducedFluorescence OR ionassisted chemistry/ mass spec OR long pathdifferential absorption

1-60 sec + 100 m –6 km

Hydroperoxylradical(HO2)

Conversion toOH;Selected IonChemical IonizationMass Spectrometry(SICIMS)

Ozone(O3)

Ultraviolet Photometry2 ppb Detection Limit

(DL)

1-60 sec + 100 m –6 km

Sulfuric acid(H2SO4)

SICIMS or TraceAtmospheric GasAnalyzer (TAGA)1.5 ppt DL

1-60 sec + 100 m -6 km

Ammonia(NH3)

TAGA/500 ppt DL orAtmospheric PressureChemical IonizationMass Spectrometer(API-MS)

1-60 sec + 100 m –

6 km

Nitric acid(HNO

3)

SICIMS 10 ppt; TAGA100 ppt DL

1-60 sec + 100 m –6 km

Nitric oxide(NO)

Chemiluminescence10 ppt DL

1-30 sec + 100 m –6 km

Nitrogen dioxide(NO2)

UV-Photolysis followedby chemiluminescence50 ppt DL

4-30 sec + 400 m6 km

Total NOy Molybdenum catalyst;chemiluminescence50 ppt DL

1-60 sec + 100 m –6 km

Sulfur dioxide(SO2)

Pulsed Fluorescence200 ppt DL also

TAGA/100 ppt DL

15-60 sec + 1.5 –6 km

Carbon monoxide(CO)

Gas-filter correlation15 ppb DL or long pathvacuum UV absorption(DACOM) or reducinggas detector

30-60 sec + 3-6 km

Cont'd...



TAP Program Plan

82

Table B2. Techniques for Characterization of Gas-Phase Species, Cont'd.

Measurand Technique TimeResolution

AirbornePlatform

SpatialResolution

Formaldehyde(HCHO

Derivatization; HighPressure LiquidChromatography(HPLC) or TunableDiode Laser

20-120 s

Hydrogen peroxide(H2O2)

Glass ScrubberSelective Derivatization Fluorimetry60 ppt DL

60 sec + 6 km

Hydrocarbons Canister/Capillary GasChromatograph10-100 ppt DL

30-90 s +

Carbonyls Glass ScrubberHigh Pressure LiquidChromatography10-20 ppt

180 sec + 18 km

Dimethylsulfide(DMS)

TAGA2 ppt DL

20-60 sec + 2-6 km

Nitrous acid(HNO2)

TAGA500 ppt DL

20-60 sec + 2-6 km

Formic acid;acetic acid(HCOOH,CH3COOH

TAGA25 to 30 ppt DL

20-60 sec + 2-6 km

Peroxyacetylnitrate

(PAN)

Need 0.05-70 ppb

Nitrate radical(NO3)

Need 5-430 ppt

Polycyclic AromaticHydrocarbons

Radon




83

Table B3. Techniques for Characterization of Meteorological Processes


AirbornePlatform

SpatialResolution

Real-Time AirParcel Trajectory

Air parcel x,y,zposition with time

Smart Balloon/ Perfluorocarbon orTracer Tagging

1-60 sec + 100 m –

6 km

Boundary LayerMixing Height

Boundary LayerHeight

Lidar 1-60 sec + 100 m –

6 km

Boundary LayerMixing andStratification

Vertical Profile ofTemperature, RH,wind speed, winddirection

Radio AcousticSounding System/ Rawinsonde/ TetheredBalloon

1-60 sec + 100 m -6 km

Entrainment at Topof Boundary Layer

Water Vapor orOzone

Fast water vapor orozone concentrations atBL top

100 m –

6 km

Vertical Profile ofWinds

Horizontal windspeed and directionwith altitude

Sodar

Local SourceRegion

Surface HorizontalWind Speed andDirection

Anemometer 1 sec + 100 m

Air MassThermodynamicState

Temperature, DewPoint Temperature,Pressure

Various 1 sec + 100 m

Boundary LayerHeight; VerticalProfile of BLThermodynamicState

Temperature, DewPoint Temperature,Wind Speed, WindDirection as afunction ofPressure

Rawinsonde

Tethered Balloon

Aircraft Vertical Profiles

4 hr

Continuous

15 min

+

Precipitation Volume ofprecipitation overknown time

Tipping Bucket 0.01” precip NO

Synoptic ScaleForcing

National WeatherService StandardSynoptic pressureanalyses –variation ofgeopotential height

along isobars

NWS analysis of surfaceand upper air pressurefields using rawinsondedata

6 hr NO

Cloud Processingand PrecipitationAlong BackTrajectory

Cloud arealcoverage, altitude,thickness andprecipitation fromradar reflectance

Regional NEXRADimages

~ minutes NO

Cont'd...



TAP Program Plan

84

Table B3. Techniques for Characterization of Meteorological Processes, Cont'd.


AirbornePlatform

SpatialResolution

Model PredictedAir Mass Back

Trajectory

Air mass x, y, and zposition with time

Model Onetrajectory/

hour

NO Each majorsampling site

Synoptic scaleForcing/FreeTroposphere –TroposphereExchange; CloudVenting

Visible and IRreflectance

Hemispheric andRegional NWS andother Satellites

~Hours ~50-100’s km

Cloud Venting andSubsidence; CloudTop Entrainment;Cloud Bottom In-Flow

Flux of water vaporout of top andpossibly sides ofcloud; downwardflux around cloud

Above cloud eddycorrelation using aircraftgust probe and fastresponse water vapor

5 ms ? 0.5 m

CloudMicrophysics;cloudsupersaturation

Cloud UpdraftVelocity

Gust Probe 5 ms + 0.5 m

PhotochemicalPotential

Downwelling SolarRadiance

+

VerticalTemperatureProfile; CirrusCloud Properties

Upwelling InfraredRadiance; Cirrusthickness,transmissivity andareal coverage

Satellite IR sensor




85

Appendix C

Relationship between TAP and other

Federally Funded PM Research ProgramsA number of related research programs directed to research on atmospheric particulate matter arecurrently conducted by various Federal agencies. According to the recently published Inventory ofFederal Research Programs prepared by the Air Quality Research Subcommittee (AQRS, 1998) of theCommittee on the Environment and Natural Resources, approximately $26M was devoted to processresearch pertinent to aerosol formation and $4M to exposure assessment and risk analysis. Thedistribution of resources among the PM process-related research is shown in Figure C1.

Emissions15%

SourceApportionment

16%

MethodDevelopment

13%

FieldStudies

27%

Chemistry andProcesses

19%

Modeling10%

Figure C1. Allocation of resources within atmospheric process research on particulate matter in

the Federal sector. Adapted from AQRS(1998).

Much complementary research is conducted under the aegis of global change research (SGCR, 2000).The various projects and respective funding agencies are presented in Table C1 categorized according tothe project research focus.



TAP Program Plan

86

Table C1. Compilation of Federal Agency Research Projects on atmospheric Particulate Matter, groupedaccording to research focus. Adapted from AQRS(1998).

Component Program/Effort Agency $, M1998

Geographicalscale

Methods andMonitoring

IMPROVE NPS/DOI 1.24 National

AIRMoN, chemicaldeposition by particles

NOAA 0.2 National

ARM/PM DOE/OBER 1.0 National

PM2.5 Sampling/Analysis DOE/NETL 1.5 Ohio RiverValley

Southern Oxidants StudyPM

EPA/ORD 0.4 Southeast

New PM Analytical

Methods

EPA/ORD 1.0

Exploratory Grants on PMEnvironmentalcharacterization andmeasurement Method

EPA/ORD 2.1

FRM and Equivalencyprogram for PM2.5

EPA/ORD 0.37

FRM MonitoringPartnerships andRegional Supersite

TVA 0.23 TennesseeValley region

PM Remote Sensing NASA Global

Chemistry,Meteorology, andModeling

Processes of fine PMformation and distribution

NOAA, AirQuality

0.45 National

Observations andModeling

NOAA,GlobalChange

0.95 National

Processes andDistribution

NASA /GACP

2.0 Global

ACP/Aerosol/Indirect DOE/OBER 2.0/4.0 National

Processes affecting pestcontrol application

USDA

Formation, Fate, andComposition ofTropospheric PM

NSF 1.5 Regional,Global

Organic AerosolsChemistry for Multi-ScaleModeling

EPA/ORD 0.5 National

Models-3/CMAQ for PM EPA/ORD 1.7 National

EMP-indirect DOE/OBER 2.0 National




87

Table C1, cont'd. Compilation of Federal Agency Research Projects on atmospheric Particulate Matter,grouped according to research focus. Adapted from AQRS(1998).

Component Program/Effort Agency $, M1998

Geographicalscale

Chemistry,Meteorology, andModeling (cont'd)

Exploratory grants on PMatmospheric chemistryand modeling

EPA/ORD 1.15

EmissionCharacterization &SourceApportionment

BRAVO NPS/DOI 0.9 Big BendNational Park

Origins and Dispersion ofPrimary PM

NOAA/DOC 0.2 National

Smoke Management and

Air Quality

USDA 1.9 National

Wind Erosion and AirQuality Prediction

USDA 0.8 WA

Emissions from CottonGinning

USDA 0.05 TX, OK, NM

Receptor Modeling andSource Chemical Profiles


Source Apportionmentand CMB Analysis ofUrban Sources


PM Emissions from

Indoor and OutdoorSources


Source, Formation, andTransport in theTennessee Valley

TVA 0.5 TennesseeValley region

A major portion of programs that are identified as field studies are carried out primarily for monitoringpurposes, e.g., the IMPROVE program, as distinguished from research directed to aerosol evolution in theatmosphere. Only limited research effort is directed to gaining a quantitative understanding of the lifecycle of aerosols in a geographical scale of ~200 km based on a detailed field measurements involving acomprehensive suite of chemical and meteorological measurement platforms. TAP is complementary tomany ongoing projects in a number of ways. For example, method and model development are anintegral part of the TAP effort, and emission characterization and source apportionment will in someinstances serve as model inputs and in others be tested by field observation data.

Reference

AQRS (1998). Air Quality Research Subcommittee, Committee on Environment and Natural Resources.Atmospheric Particular Matter Research: Inventory of Federal Research Programs. September, 1998.



TAP Program Plan

TAP Tropospheric Aerosol Program

TDM TAP Data Management

TEM Transmission Electron Microscopy

TEOM Tapered Element Oscillating Microbalance

TOF-MS Time-Of-Flight Mass Spectrometry

TSS TAP Science Support

TST TAP Science Team

TVA Tennessee Valley Authority

USDA United States Department of Agriculture

USGCRP U.S. Global Change Research Program

UTC Universal Time Coordinated

VOC volatile organic compound

VTMX Vertical Transport and Mixing Programwithin DOE/OBER/ESD

chemtrails - 05.06.04 - tap program plan (t

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