noaa collaborative mercury sites · keystone pa brandon shores md homer city pa conemaugh pa...

Canaan Valley Institute-NOAA

BeltsvilleEPA-NOAA

Three sites committed to speciated mercury

ambient concentration measurement network

Grand BayNOAA

NOAA Collaborative Mercury SitesNOAA Collaborative Mercury Sites

coal

incinerator

metals

manuf/other

Symbol colorindicates typeof mercury source

1 - 5050 - 100

100 - 200

200 – 400

400 - 700

700 – 1000

> 1000

Symbol size andshape indicates 1999 mercuryemissions, kg/yr

rural AQS

NADP/MDN

CASTNet

IMPROVE

Monitoring sites

other AQS

Hg site

Beltsville, MDBeltsville, MDCASTNet SiteCASTNet Site

100 miles from DC

Bremo

Beltsville monitoring site

Morgantown

Chalk Point

Dickerson

Possum Point

Eddystone

Arlington - Pentagon MSW Incin

Brandon Shores and H.A. Wagner

Montgomery CountyMSW Incin

Harford County MSW Incin

KEYSTONE PA

Brandon Shores MD

HOMER CITY PA

CONEMAUGH PA

MONTOUR PA

Morgantown MD

BRUNNER ISLAND PA

HATFIELDS FERRY PA

BRUCE MANSFIELD PA

CHALK POINT MD

SHAWVILLE PA

PORTLAND PA

DICKERSON MD

EDDYSTONE PA

MARTINS CREEK PA

COLVER PA

TITUS PA

NORTHAMPTON PA

Wagner Station MD

SUNBURY PA

NESQUEHONING PA

KENNERDELL PA

JOHN B RICH PA

CROMBY PA

COGENTRIX RICHMOND VA

AES WARRIOR RUN MD

CHESTERFIELD VA

ARMSTRONG PA

CHESWICK PA

R. PAUL SMITH MD

READING ANTHRACITE PA

MITCHELL PA

FOSTER WHEELER MT CA PA

POTTER PA

POTOMAC RIVER VA

ELRAMA PA

HUNLOCK CREEK PA

CAMBRIA COGEN PA

EBENSBURG COGEN PA

MCADOO CO GEN PA

0

100

200

300

400

500

600

2010

: BA

SE

- C

AIR

(kg/

year

)

Hg(0)Hg(2)Hg(p)

CoalCoal--fired power plants in MD, fired power plants in MD, VA, PA, and DE with the largest VA, PA, and DE with the largest projected differences between projected differences between 2010 base and 2010 Clean Air 2010 base and 2010 Clean Air Interstate Rule (CAIR) emissionsInterstate Rule (CAIR) emissions

Morgantown

Brandon Shores

Chalk Point

Dickerson H.A. Wagner

Beltsville monitoring

site

Brandon Shores

Chalk Point

Morgantown

Dickerson H. A. Wagner

SOSO4422--, NO, NO33

--, NH, NH44++, HNO, HNO33, SO, SO22 (Weekly) (Weekly)

Relative HumidityRelative HumidityWind DirectionWind DirectionWind speedWind speedNitrogen Oxides (NO, Nitrogen Oxides (NO, NOyNOy))Carbon MonoxideCarbon MonoxideOzoneOzoneSulfur dioxideSulfur dioxideReactive gaseous mercuryReactive gaseous mercury

Elemental mercuryElemental mercury

Major ions in precipitation (weekly)Major ions in precipitation (weekly)Total mercury in precipitation (weekly)Total mercury in precipitation (weekly)

PrecipitationPrecipitationTemperatureTemperature

Fine particulate mercuryFine particulate mercury

MeasurementMeasurement

Status of Atmospheric MeasurementsStatus of Atmospheric Measurementsat Beltsville, MD CASTNet Siteat Beltsville, MD CASTNet Site

TekranTekran Speciation SystemSpeciation System

•• Installed System 1 (NOAA) Nov. 7, 2006Installed System 1 (NOAA) Nov. 7, 2006Height of Inlet: 3.75 m above groundHeight of Inlet: 3.75 m above ground

0.5 m above trailer0.5 m above trailer

•• Installed second systemInstalled second system(System 2(System 2--NOAA) Jan 26, 2007NOAA) Jan 26, 2007

•• System 1 removed April 27, 2007System 1 removed April 27, 2007

•• Install System 3 (EPA) June 1, 2007Install System 3 (EPA) June 1, 2007

•• Remove System 2 August 17, 2007Remove System 2 August 17, 2007

TekranTekran Deployment Timeline Deployment Timeline --BeltsvilleBeltsvilleNOV2006

DEC JAN2007

FEB MAR APR MAY JUN JUL AUG SEP OCT

System 1

System 2

System 3

NO Diurnal Profile -Beltsville

0

2

4

6

8

10

12

14

16

18

20

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24EST Hour

[NO

] (pp

b)

FallWinterSpringSummer

Site is influenced by vehicular Site is influenced by vehicular traffic in Washington traffic in Washington Metropolitan area, particularly Metropolitan area, particularly pronounced during the morning pronounced during the morning rush hour. Higher boundary rush hour. Higher boundary layer in the afternoon/evening layer in the afternoon/evening dilutes vehicular emissions. dilutes vehicular emissions.

-100

100

100 100

80 ppb60

40

NOY

CO Diurnal Profile -Beltsville

0

50

100

150

200

250

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24EST Hour

[CO

] (pp

b)

SpringSummer

Concentrations of CO at the Concentrations of CO at the site also reflect the impact of site also reflect the impact of vehicular emissions, but the vehicular emissions, but the efficacy of emission controls in efficacy of emission controls in the past decade have reduced the past decade have reduced the strength of this signal.the strength of this signal.

-600

600

600 600

400200

600 ppb

CO

SO2 Diurnal Profile -Beltsville

0

1

2

3

4

5

6

7

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24EST Hour

[SO

2] (p

pb)

WinterSpringSummerFall

Site is also influenced by Site is also influenced by pointpoint--source emitters in source emitters in the region. Higher the region. Higher concentrations in Fall and concentrations in Fall and Winter reflect lower Winter reflect lower boundary layer heights, boundary layer heights, slower conversion of SOslower conversion of SO22to SOto SO44

22--

-50

-40

-30

-20

-10

0

10

20

30

40

50

50 -40 -30 -20 -10 0 10 20 30 40 5

102030

40 ppbSO2

O3 Diurnal Profile -Beltsville

0

10

20

30

40

50

60

70

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24EST Hour

[O3]

(ppb

)WinterSpringSummerFall

Photochemical ozone generation in the Spring and Summer Photochemical ozone generation in the Spring and Summer leads to elevated concentrations in midleads to elevated concentrations in mid--day. Note the later day. Note the later time of boundary layer breakup in Fall and Winter, as time of boundary layer breakup in Fall and Winter, as evidenced by later onset of daytime increase. evidenced by later onset of daytime increase.

Beltsville Time Series

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

2006.83 2006.92 2007.00 2007.08 2007.17 2007.25 2007.33 2007.42 2007.50 2007.58 2007.67Decimal Year

Hg0

(ng

m-3

)

Sytem 1System 2System 3

Nov Dec Jan Feb Mar Apr May Jun Jul Aug

Elemental Hg0

Hg0 Diurnal Profile -Beltsville

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24EST Hour

Hg0

(ng

m-3

)

WinterSpringSummer

Hg0 Rose, All Data -Beltsville

-4

4

-4 4

Hg0 (ng m-3)

Hg0

(ng

m-3

)

12

34 ng m-3

Elemental Mercury (HgElemental Mercury (Hg00) at Beltsville) at Beltsville

As expected, Hg0 at Beltsville shows no diurnal As expected, Hg0 at Beltsville shows no diurnal pattern, little dependence on WD, consistent with a pattern, little dependence on WD, consistent with a longlong--lived, ubiquitous, and well mixed trace lived, ubiquitous, and well mixed trace species. Note that emission source regions match species. Note that emission source regions match those for SOthose for SO22, NO, NOYY, CO, CO


-20

0

20

40

60

80

100

120

140

160

180

200

220

240

2006.83 2006.92 2007 2007.08 2007.17 2007.25 2007.33 2007.42 2007.5 2007.58 2007.67Decimal Year

Hg-

P (p

g m

-3)



Hg-P(a few peaks > 500 pg m-3 not shown)

Hg-P Diurnal Profile -Beltsville

0

5

10

15

20

25

30

35

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24EST Hour

Hg-

P (p

g m

-3)

WinterSpringSummer

Little diurnal variation in HgLittle diurnal variation in Hg--P concentrations, with some P concentrations, with some evidence of entrainment of higher concentrations aloft evidence of entrainment of higher concentrations aloft beginning in the morning, after the breakup of the nocturnal beginning in the morning, after the breakup of the nocturnal inversion. Spikes due to influence of a few highinversion. Spikes due to influence of a few high--concentration events. concentration events.

Particulate Mercury (HgParticulate Mercury (Hg--P)P)

Hg-P Rose, All Data

-200

-200

Hg-P (pg m-3)

Hg-

P (p

g m

-3)

50100

150200

Hg-P vs SO2 Beltsville

0

20

40

60

80

100

120

140

160

180

200

0 5 10 15 20 25 30 35SO2 (ppb)

[FPM

] (pg

m-3

)

All DataAll Data

Hg-P vs SO2 Beltsville

0

20

40

60

80

100

120

140

160

180

200

0 5 10 15 20 25 30 35SO2 (ppb)

[FPM

] (pg

m-3

)

WinterWinter

HgHg--P concentrations are P concentrations are highest during NE flow, highest during NE flow, consistent with the consistent with the distribution of local/regional distribution of local/regional sources. Concentrations show sources. Concentrations show some association with SOsome association with SO22, , especially in Winter. Power especially in Winter. Power plants emit little Hgplants emit little Hg--P.P.



-200

20406080

100120140160180200220240260

2006.86 2006.95 2007.03 2007.11 2007.20 2007.28 2007.36 2007.45 2007.53 2007.61Decimal Year

RG

M (p

g m

-3)



RGM

RGM concentrations generally < 20 pg mRGM concentrations generally < 20 pg m--33, with more , with more frequent peaks in concentration than was seen for Hgfrequent peaks in concentration than was seen for Hg--PP

RGM Diurnal Profile -Beltsville

0

5

10

15

20

25

30

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24EST Hour

RG

M (p

g m

-3)

WinterSpringSummer

More pronounced diurnal variation in RGM concentrations, More pronounced diurnal variation in RGM concentrations, again showing evidence of entrainment of higher concentrations again showing evidence of entrainment of higher concentrations aloft with the breakup of the nocturnal inversion. Large seasonaaloft with the breakup of the nocturnal inversion. Large seasonal l differences may point to secondary (photochemical) source of differences may point to secondary (photochemical) source of RGM as well.RGM as well.

Reactive Gaseous Mercury (RGM)Reactive Gaseous Mercury (RGM)

RGM vs NO/NOy Beltsville

0

50

100

150

200

250

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1NO/NOY

[RG

M] (

pg m

-3)

All Data Spring

0

50

100

150

200

250

0 10 20 30 40 50 60 70 80 90 100 110 120[O3] (ppb)

[RG

M] (

pg m

-3)

SpringBeltsville SpringAll Data

Association of high RGM with high OAssociation of high RGM with high O33 and aged air masses and aged air masses (low NO/NO(low NO/NOYY ratios) suggests that secondary production of ratios) suggests that secondary production of RGM may be occurring. RGM may be occurring.

However, high concentrations of RGM may arise from However, high concentrations of RGM may arise from primary emissions from sources a few hours away primary emissions from sources a few hours away –– and the and the air masses are somewhat aged on arrival at the site.air masses are somewhat aged on arrival at the site.

increasing air mass age

RGM Rose, All Data

-250

250

-250 250

RGM (pg m-3)

RG

M (p

g m

-3)

50100

150200 pg m-3

Directionality of Directionality of [RGM] shows lobes to [RGM] shows lobes to the SW and NE, the SW and NE, coincident with known coincident with known local sources of local sources of mercury and other mercury and other primary trace species.primary trace species.

RGM is most closely RGM is most closely associated with SOassociated with SO22 at at Beltsville (Summer) Beltsville (Summer) suggesting that pointsuggesting that point--source emissions also source emissions also play an important role play an important role in influencing RGM in influencing RGM concentrations at the concentrations at the sitesite

RGM vs SO2 Beltsville

0

50

100

150

200

250

0 5 10 15 20 25 30 35[SO2] (ppb)

[RG

M] (

pg m

-3)

SummerSummer

Reactive Gaseous Mercury Reactive Gaseous Mercury (RGM)(RGM)

Barry

Holcim Cement

NOAA Grand BayNERR Hg site

WeeksBay

OLF

Molino

Pace

Ellyson

Jack Watson

AL24

AL02

Crist

Pascagoula MSW incin

haz waste incin

paper manufpaper manuf

Victor J. Daniel

MobileBay

Mobile

Pascagoula

Mississippi Alabama

NOAA

SEARCH

USGS

UWF/FSU

MDN

Monitoring Site

coal-fired power plant

waste incinerator

manufacturing

metallurgical

other fuel combustion

type of mercuryemissions source

total atmosphericmercury emissions (kg/yr, 1999 EPA NEI)

50 - 100

100 - 200

200 - 400

1 – 50

MS 22

Grand Bay Grand Bay NERR SiteNERR Site

BB

BB

CC

CC

CC

CC

CC

AA

AA

AA

AA

AA

AA

AA

TypeType

Feb 2007Feb 2007Relative HumidityRelative Humidity

Feb 2007Feb 2007Wind DirectionWind Direction

Feb 2007Feb 2007Wind speedWind speed

**Nitrogen Oxides (NO, Nitrogen Oxides (NO, NOyNOy))

Oct 2006Oct 2006Carbon MonoxideCarbon Monoxide

Oct 2006Oct 2006OzoneOzone

Oct 2006Oct 2006Sulfur dioxideSulfur dioxide

Sept 2006Sept 2006Reactive gaseous mercuryReactive gaseous mercury

Sept 2006Sept 2006Elemental mercuryElemental mercury

**Major ions in precipitationMajor ions in precipitation

**Total mercury in precipitationTotal mercury in precipitation

Feb 2007Feb 2007PrecipitationPrecipitation

Feb 2007Feb 2007TemperatureTemperature

Sept 2006Sept 2006Fine particulate mercuryFine particulate mercury

Start DateStart DateMeasurementMeasurement

Type of Measurement:A = concentration in ambient airB = concentration in precipitationC = meteorological parameter

Status of Atmospheric MeasurementsStatus of Atmospheric Measurementsat Grand Bay NERR, Mississippiat Grand Bay NERR, Mississippi

* to be established

4 m sampling height

Pollution Rose Hg0-All Data

-5

-4

-3

-2

-1

0

1

2

3

4

5

-5 -4 -3 -2 -1 0 1 2 3 4 5

As expected, with a few exceptions HgAs expected, with a few exceptions Hg00 concentrations show concentrations show little or no diurnal variation or dependence on wind directionlittle or no diurnal variation or dependence on wind direction

Elemental Mercury (HgElemental Mercury (Hg00) at Grand Bay) at Grand Bay

Diurnal Average Values, Hg0

0

0.5

1

1.5

2

2.5

3

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24CST Hour

[Hg0

] (ng

m-3

)


0

1

2

3

4

5

6

7

8

9

10

0 100 200 300 400 500 600[CO] (ppb)

[Hg0

] (ng

m-3

)

0

1

2

3

4

5

6

7

8

9

10

0 10 20 30 40 50 60 70 80 90 100[O3] (ppb)

[Hg0

] (ng

m-3

)

Overnight EventOvernight EventFeb. 28Feb. 28--March 1March 1

Strong correlation Strong correlation between Hgbetween Hg00 and CO, and CO, OO33..

Suggests combustion Suggests combustion (natural sources?) and (natural sources?) and transport from source transport from source regions to regions to West. RGM, HgWest. RGM, Hg--P P ca 20 pg mca 20 pg m--33

during episodeduring episode

Hg-P Correlation with O3 -Grand Bay

0102030405060708090

100110120130140150

0 10 20 30 40 50 60 70 80 90 100[O3] (ppb)

[Hg-

P] (p

g m

-3)

Hg-P Correlation with SO2 -Grand Bay

0102030405060708090

100110120130140150

0 2 4 6 8 10 12 14 16 18 20[SO2] (ppb)

[Hg-

P] (p

g m

-3)

All DataAll Data

With the exception of a few With the exception of a few wellwell--defined transport defined transport events, Hgevents, Hg--P displays no P displays no consistent relationship consistent relationship with wind direction, and with wind direction, and exhibits little or no exhibits little or no correlation with other correlation with other trace speciestrace species


Pollution Rose Hg-P-All Data

-100

-80

-60

-40

-20

0

20

40

60

80

100

100 -75 -50 -25 0 25 50 75 100

RGM Correlation with O3 -Grand Bay

0102030405060708090

100110120130140150

0 10 20 30 40 50 60 70 80 90 100

[O3] (ppb)

[RG

M] (

pg m

-3)

RGM, All Data

Strongest correlations seen Strongest correlations seen between RGM and Obetween RGM and O33, most of , most of which is driven by seasonal which is driven by seasonal dependence dependence ––RGM RGM concentrations are highest, concentrations are highest, relationship with Orelationship with O33 is is strongest in Spring.strongest in Spring.

RGM Correlation with O3 -Spring

0102030405060708090

100110120130140150

0 10 20 30 40 50 60 70 80 90 100

[O3] (ppb)

[RG

M] (

pg m

-3)

Spring

All Data

0102030405060708090

100110120130140150

0 50 100 150 200 250 300 350 400 450 500

[CO] (ppb)

[RG

M] (

pg m

-3)

Spring 2007

0102030405060708090

100110120130140150

0 10 20 30 40 50 60 70 80 90 100

RH (%)

[RG

M] (

pg m

-3)

Spring 2007 Association of peak Association of peak RGM with low RH and RGM with low RH and CO concentrations CO concentrations typical of continental typical of continental influence suggests influence suggests highest Spring peaks of highest Spring peaks of RGM are seen in postRGM are seen in post--frontal activity, with frontal activity, with transport from upwind transport from upwind continental sources to continental sources to the North. the North.

What is the role of What is the role of downward mixing of downward mixing of upperupper--tropospherictropospheric air, air, which contains elevated which contains elevated RGM, ORGM, O33, and lower CO , and lower CO and RH ? and RH ?

Spring

Spring

RGM Correlation with SO2 -Grand Bay

0102030405060708090

100110120130140150

0 1 2 3 4 5 6 7 8 9 10

[SO2] (ppb)

[RG

M] (

pg m

-3)

SprSpring

RGM Correlation with Hg-P -Grand Bay

0102030405060708090

100110120130140150

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150[Hg-P] (pg m-3)

[RG

M] (

pg m

-3)

All Data

Weaker RGM Weaker RGM –– SOSO22correlation at Grand Bay correlation at Grand Bay than at Beltsville suggests:than at Beltsville suggests:

A mix of primary sources with A mix of primary sources with varying emission characteristicsvarying emission characteristics

A mix of primary and A mix of primary and secondary sources of RGMsecondary sources of RGM

Different chemical processing Different chemical processing and removal rates of SOand removal rates of SO22 and and RGM during transportRGM during transport

Lack of correlation Lack of correlation ––RGM RGM and Hgand Hg--P suggests differentP suggests differentsources and/or removal ratessources and/or removal ratesof these speciesof these species

Diurnal Average Values, Hg-P

0

2

4

6

8

10

12

14

16

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24CST Hour

[Hg-

P] (p

g m

-3)


Diurnal Average Values, RGM

0

2

4

6

8

10

12

14

16

18

20

22

24

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24CST Hour

[RG

M] (

pg m

-3)


As at Beltsville, As at Beltsville, significant diurnal significant diurnal patterns seen in RGM, patterns seen in RGM, but amplitude of diurnal but amplitude of diurnal HgHg--P profile is much P profile is much smaller.smaller.

Highest RGM and HgHighest RGM and Hg--P P concentrations seen in concentrations seen in Spring. At Beltsville, Spring. At Beltsville, HgHg--P peaks in the P peaks in the winter, and Springwinter, and Spring--Summer differences Summer differences between RGM and Hgbetween RGM and Hg--P P are smallare small

Diurnal Average Values, SO2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24CST Hour

[SO

2] (p

pb)


Diurnal Average Values, O3

0

5

10

15

20

25

30

35

40

45

50

55

60

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24CST Hour

[O3]

(ppb

)


Similarity to OSimilarity to O33 and SOand SO22diurnal profiles diurnal profiles confirms the importance confirms the importance of downward mixing in of downward mixing in the development of the the development of the daytime boundary layer, daytime boundary layer, but photochemical but photochemical (secondary) production (secondary) production of RGM is also possibleof RGM is also possible

•• Beltsville site is semiBeltsville site is semi--urban and is ringed by emission sources of mercury urban and is ringed by emission sources of mercury and other primary trace species, with frequent peaks in RGM (lesand other primary trace species, with frequent peaks in RGM (less for Hgs for Hg--P) P) concentrations due to transport from nearby sources. Grand Bay Nconcentrations due to transport from nearby sources. Grand Bay NERR Site ERR Site exhibits characteristics of a rural/remote site with low concentexhibits characteristics of a rural/remote site with low concentrations of all rations of all species but occasional transport related episodes of higher concspecies but occasional transport related episodes of higher concentrations.entrations.

•• At both sites, RGM exhibits a more pronounced diurnal profile thAt both sites, RGM exhibits a more pronounced diurnal profile than Hgan Hg--P, P, but both profiles are coincident with Obut both profiles are coincident with O33 and SOand SO22 peaks, suggesting peaks, suggesting downward mixing of an aloft reservoir upon the breakup of the nodownward mixing of an aloft reservoir upon the breakup of the nocturnal cturnal boundary layer. In situ production of RGM may also be contributiboundary layer. In situ production of RGM may also be contributing. RGM ng. RGM peaks in the Spring at Grand Bay, in Spring and Summer at Beltsvpeaks in the Spring at Grand Bay, in Spring and Summer at Beltsville. Hgille. Hg--P P is higher in Winter at Beltsville.is higher in Winter at Beltsville.

•• At Beltsville, RGM correlates most closely with SOAt Beltsville, RGM correlates most closely with SO22 in Summer, suggesting in Summer, suggesting the dominance of nearby (primary) emissions. However, RGM is alsthe dominance of nearby (primary) emissions. However, RGM is also o associated with elevated Oassociated with elevated O3 3 and low NO/and low NO/NOyNOy ratios, suggesting that ratios, suggesting that secondary production may also be importantsecondary production may also be important

Summary and Conclusions Summary and Conclusions ––Interpretation of Ambient MeasurementsInterpretation of Ambient Measurements

•• At Grand Bay, RGM is associated with OAt Grand Bay, RGM is associated with O33 in Springtime, and is associated in Springtime, and is associated with dryer air characteristic of continental emissions (CO ca 20with dryer air characteristic of continental emissions (CO ca 200 ppb).0 ppb).

•• These results suggest RGM is transported from northerly continenThese results suggest RGM is transported from northerly continental tal sources following coldsources following cold--frontal penetration in Spring. Reduced frequency of frontal penetration in Spring. Reduced frequency of cold frontal passage at the site in Summer leads to lower RGM lecold frontal passage at the site in Summer leads to lower RGM levels, more vels, more sporadic transport to the site from upwind sources.sporadic transport to the site from upwind sources.

Summary and Conclusions Summary and Conclusions ––Interpretation of Ambient MeasurementsInterpretation of Ambient Measurements

(continued....)(continued....)

Deposition EstimatesDeposition Estimates

RGM + HgRGM + Hg--P Dry Deposition (P Dry Deposition (ngng mm--22 dayday--11););assumes assumes VVdd = 2.5 cm s= 2.5 cm s--11 and 0.3 cm sand 0.3 cm s--11 mid day averagemid day average

Fluxes (Fluxes (ngng mm--22 dayday--11))FallFall Winter Spring SummerWinter Spring Summer

Dry Dry DepDep, Beltsville (2006, Beltsville (2006--2007)2007) 7.87.8 22.322.3 18.218.2Wet Wet DepDep, Beltsville (2005, Beltsville (2005--2006)2006) 35.435.4 13.913.9 13.013.0 54.8 54.8

Preliminary Deposition Preliminary Deposition EstimatesEstimates --BeltsvilleBeltsvilleRGM Diurnal Profile -Beltsville

0

5

10

15

20

25

30

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24EST Hour

RG

M (p

g m

-3)

WinterSpringSummer

Diurnal Average Values, RGM

0

2

4

6

8

10

12

14

16

18

20

22

24

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24CST Hour

[RG

M] (

pg m

-3)


RGM + HgRGM + Hg--P Dry Deposition (P Dry Deposition (ngng mm--22 dayday--11););assumes assumes VVdd = 2.5 cm s= 2.5 cm s--11 and 0.3 cm sand 0.3 cm s--11 mid day averagemid day average

Fluxes (Fluxes (ngng mm--2 day2 day--1)1)FallFall Winter Spring SummerWinter Spring Summer

Dry Dry DepDep, Grand Bay (2006, Grand Bay (2006--2007)2007) 5.45.4 4.34.3 14.214.2 8.68.6Wet Wet DepDep, AL24 (2005, AL24 (2005--2006)2006) 13.513.5 24.824.8 31.631.6 34.634.6Wet Wet DepDep, MS22 (2005, MS22 (2005--2006) 2006) 11.911.9 28.228.2 28.528.5 65.365.3Wet Wet DepDep, AL02 (2005, AL02 (2005--2006)2006) 24.724.7 21.621.6 31.331.3 34.634.6

Preliminary Deposition Preliminary Deposition EstimatesEstimates --Grand BayGrand Bay

•• Preliminary estimates of dry deposition have been made based Preliminary estimates of dry deposition have been made based on measured RGM and Hgon measured RGM and Hg--P concentrations. More P concentrations. More sophisticated estimates will be made in the future.sophisticated estimates will be made in the future.

•• Dry deposition estimates, when compared with nearby MDN Dry deposition estimates, when compared with nearby MDN deposition records, suggest that dry deposition sometimes deposition records, suggest that dry deposition sometimes dominates at the Beltsville site, depending on season.dominates at the Beltsville site, depending on season.

•• At Grand Bay, wet deposition dominates the removal of At Grand Bay, wet deposition dominates the removal of reactive mercury species, especially in Winter. reactive mercury species, especially in Winter.

•• If substantial Hg exists in the coarse aerosol fraction, howeverIf substantial Hg exists in the coarse aerosol fraction, however, , the reported dry deposition fluxes are underthe reported dry deposition fluxes are under--estimated.estimated.

Summary and Conclusions Summary and Conclusions -- DepositionDeposition

Trajectory Analysis Trajectory Analysis Examples: BeltsvilleExamples: Beltsville

Beltsville Episode January 7, 2007

07:

30 0

8:30

09:

30 1

0:30

11:

30 1

2:30

13:

30 1

4:30

15:

30 1

6:30

(Eastern Standard Time)January 7, 2007

0

20

40

60

80

100

RG

M (p

g/m

3)

07:

30 0

8:30

09:

30 1

0:30

11:

30 1

2:30

13:

30 1

4:30

15:

30 1

6:30

(Eastern Standard Time)January 7, 2007

0

20

40

60

80

100

RG

M (p

g/m

3)

Beltsville Episode May 18, 2007

07:

30 0

8:30

09:

30 1

0:30

11:

30 1

2:30

13:

30 1

4:30

15:

30

(Eastern Standard Time)May 18, 2007

01020304050607080

RG

M a

nd F

PM

(pg/

m3)

FPMRGM

07:

30 0

8:30

09:

30 1

0:30

11:

30 1

2:30

13:

30 1

4:30

15:

30

(Eastern Standard Time)May 18, 2007

01020304050607080

RG

M a

nd F

PM

(pg/

m3)

FPMRGM

Trajectory Analysis Trajectory Analysis Examples: Grand BayExamples: Grand Bay

Higher RGM Associated with NHigher RGM Associated with N--E trajectoriesE trajectories

Peak ~ 50 pg mPeak ~ 50 pg m--33 Peak ~ 118 pg mPeak ~ 118 pg m--33 Peak ~ 55 pg mPeak ~ 55 pg m--33


Lower RGM in Maritime trajectoriesLower RGM in Maritime trajectories


Grand Bay Episode March 6,

2007

05:3

0 A

M

07:3

0 A

M

09:3

0 A

M

11:3

0 A

M

01:3

0 P

M

03:3

0 P

M

05:3

0 P

M

07:3

0 P

M

09:3

0 P

M

11:3

0 P

M

01:3

0 A

M

03:3

0 A

M

05:3

0 A

M

0

50

100

150

GE

M (

ng/m

3 - 1

.5) *

10

RG

M a

nd F

PM

(pg/

m3)

RGM

FPM

GEM

March 6 March 7

05:3

0 A

M

07:3

0 A

M

09:3

0 A

M

11:3

0 A

M

01:3

0 P

M

03:3

0 P

M

05:3

0 P

M

07:3

0 P

M

09:3

0 P

M

11:3

0 P

M

01:3

0 A

M

03:3

0 A

M

05:3

0 A

M

0

50

100

150

GE

M (

ng/m

3 - 1

.5) *

10

RG

M a

nd F

PM

(pg/

m3)

RGM

FPM

GEM

March 7March 6

05:3

0 A

M

07:3

0 A

M

09:3

0 A

M

11:3

0 A

M

01:3

0 P

M

03:3

0 P

M

05:3

0 P

M

07:3

0 P

M

09:3

0 P

M

11:3

0 P

M

01:3

0 A

M

03:3

0 A

M

05:3

0 A

M

0

50

100

150

GE

M (

ng/m

3 - 1

.5) *

10

RG

M a

nd F

PM

(pg/

m3)

RGM

FPM

GEM

March 6 March 7

05:3

0 A

M

07:3

0 A

M

09:3

0 A

M

11:3

0 A

M

01:3

0 P

M

03:3

0 P

M

05:3

0 P

M

07:3

0 P

M

09:3

0 P

M

11:3

0 P

M

01:3

0 A

M

03:3

0 A

M

05:3

0 A

M

0

50

100

150

GE

M (

ng/m

3 - 1

.5) *

10

RG

M a

nd F

PM

(pg/

m3)

RGM

FPM

GEM

March 7March 6

18-Nov-06

12:3

0 A

M

02:3

0 A

M

04:3

0 A

M

06:3

0 A

M

08:3

0 A

M

10:3

0 A

M

12:3

0 P

M

02:3

0 P

M

04:3

0 P

M

06:3

0 P

M

08:3

0 P

M

10:3

0 P

M

010203040506070

GE

M (

ng/m

3 - 1

.5) *

10

RG

M a

nd F

PM

(pg/

m3)

RGM

FPM

GEM

Grand Bay Episode

Nov 18, 2006

18-Nov-06

12:3

0 A

M

02:3

0 A

M

04:3

0 A

M

06:3

0 A

M

08:3

0 A

M

10:3

0 A

M

12:3

0 P

M

02:3

0 P

M

04:3

0 P

M

06:3

0 P

M

08:3

0 P

M

10:3

0 P

M

010203040506070

GE

M (

ng/m

3 - 1

.5) *

10

RG

M a

nd F

PM

(pg/

m3)

RGM

FPM

GEM

Precision, QA/QC StudiesPrecision, QA/QC Studies

TekranTekran Speciation SystemSpeciation System

•• Installed System 1 (NOAA) Nov. 7, 2006Installed System 1 (NOAA) Nov. 7, 2006Height of Inlet: 3.75 m above groundHeight of Inlet: 3.75 m above ground

0.5 m above trailer0.5 m above trailer

•• Installed second system Installed second system (System 2(System 2--NOAA) Jan 26, 2007NOAA) Jan 26, 2007

•• System 1 removed April 27, 2007System 1 removed April 27, 2007

•• Install System 3 (EPA) June 1, 2007Install System 3 (EPA) June 1, 2007

•• Remove System 2 August 17, 2007Remove System 2 August 17, 2007

TekranTekran Speciation SystemsSpeciation SystemsQA/QC StudiesQA/QC Studies

•• Periodic deployment of duplicate systemsPeriodic deployment of duplicate systemsJan. 26Jan. 26--Apr. 27, 2007Apr. 27, 2007June 1June 1--Aug. 17, 2007Aug. 17, 2007

•• Precision and accuracy of independentPrecision and accuracy of independentsystemssystems

•• Investigation of aerosol size segregation ofInvestigation of aerosol size segregation ofHgHg--PP

TekranTekran Deployment Timeline Deployment Timeline --BeltsvilleBeltsvilleNOV2006

DEC JAN2007

FEB MAR APR MAY JUN JUL AUG SEP OCT

System 1

System 2

System 3

System 1, 2 Regression -Beltsville, 2007

y = 0.4514x + 0.223R2 = 0.4751

y = 0.8316x + 2.0094R2 = 0.8705

y = 0.5825x - 0.1316R2 = 0.9188

0

20

40

60

80

100

120

140

160

180

200

0 20 40 60 80 100 120 140 160 180 200[RGM] (pg m-3), System 2 (new)

[RG

M] (

pg m

-3),

Syst

em 1

(old

det

ecto

r) Original Configuration

New Denuder System 1

2 New Denuders, No Impactor System1


y = 0.9819x - 2.519R2 = 0.8851

y = 1.1917x - 0.2962R2 = 0.9295

y = 0.6662x + 1.463R2 = 0.7611

0102030405060708090

100110120130140

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140[Hg-P] (pg m-3), System 2 (new)

[Hg-

P] (p

g m

-3),

Syst

em 1

(old

det

ecto

r)

Original ConfigurationNew Denuder, Sys. 12 New Denuders, no impactor Sys 1


y = 0.8648x + 1.1992R2 = 0.9153

0

30

60

90

120

150

180

210

240

270

0 30 60 90 120 150 180 210 240 270[RGM] (pg m-3), System 2

[RG

M] (

pg m

-3),

Syst

em 3

Original ConfigurationHotter inlet, System 3Linear (Original Configuration)


y = 1.0577x + 0.6646R2 = 0.9032

0

5

10

15

20

25

30

35

40

45

50

0 5 10 15 20 25 30 35 40 45 50[Hg-P] (pg m-3), System 2

[Hg-

P] (p

g m

-3),

Syst

em 3

Original ConfigurationHotter inlet System 3Linear (Original Configuration)

Monitoring Sites:Monitoring Sites:Next StepsNext Steps

BeltsvilleBeltsville

•• Addition of 10 m walk up scaffoldAddition of 10 m walk up scaffold

•• Migration to new shelter?Migration to new shelter?

•• Acquisition of second Acquisition of second TekranTekran systemsystem

Synchronous sampling Synchronous sampling ––precision, precision, QA/QC studies, etc.QA/QC studies, etc.

Asynchronous sampling for true Asynchronous sampling for true continuous measurementscontinuous measurements

Grand BayGrand Bay

•• Migration from old trailer and site to new Migration from old trailer and site to new trailer at permanent site (watertrailer at permanent site (water’’s edge, 2 s edge, 2 miles distant)miles distant)

•• Addition of 10m walkAddition of 10m walk--up scaffoldup scaffold

•• Addition of second Addition of second TekranTekran SystemSystem

Synchronous sampling Synchronous sampling ––precision, precision, QA/QC studies, investigation of QA/QC studies, investigation of Hg/aerosol size, etc.Hg/aerosol size, etc.

Asynchronous sampling for true Asynchronous sampling for true continuous measurementscontinuous measurements

•• Addition of NO/NOAddition of NO/NOYY monitormonitor

View from top of 10 m tower looking at the southerly (prevailingView from top of 10 m tower looking at the southerly (prevailing wind) sampling wind) sampling sector over the U.S. Fish and Wildlife Service Pavilion at Grandsector over the U.S. Fish and Wildlife Service Pavilion at Grand Bay NERRBay NERR

Pictures of Permanent Monitoring Site Pictures of Permanent Monitoring Site ––Grand BayGrand Bay

Model Evaluation Model Evaluation and Improvementand Improvement

CLOUD DROPLET

cloud

PrimaryAnthropogenic

Emissions

Hg(II), ionic mercury, RGMElemental Mercury [Hg(0)]

Particulate Mercury [Hg(p)]

Re-emission of previously deposited anthropogenic

and natural mercury

Hg(II) reduced to Hg(0) by SO2 and sunlight

Hg(0) oxidized to dissolved Hg(II) species by O3, OH,

HOCl, OCl-

Adsorption/desorptionof Hg(II) to/from soot

Naturalemissions

Upper atmospherichalogen-mediatedheterogeneous oxidation?

Polar sunrise“mercury depletion events”

Br

Dry deposition

Wet deposition

Hg(p)

Vapor phase:

Hg(0) oxidized to RGM and Hg(p) by O3, H202, Cl2, OH, HCl

Atmospheric Mercury Fate Processes

1

CLOUD DROPLETCLOUD DROPLETCLOUD DROPLETCLOUD DROPLET

cloudcloudcloudcloud


Emissions


Emissions

Hg(II), ionic mercury, RGMElemental Mercury [Hg(0)]

Particulate Mercury [Hg(p)]Hg(II), ionic mercury, RGMElemental Mercury [Hg(0)]

Particulate Mercury [Hg(p)]


and natural mercury


and natural mercury




HOCl, OCl-


HOCl, OCl-



Naturalemissions

Naturalemissions

Naturalemissions




Br


Br

Dry deposition

Wet deposition

Dry deposition

Wet deposition

Hg(p)

Vapor phase:


Hg(p)

Vapor phase:


Vapor phase:


Atmospheric Mercury Fate Processes

1

AtmosphericModels

Emissions InventoriesTo evaluate and improve atmospheric models, emissions inventories must be:

• Accurate for each individual source (especially for large sources), including variations

• For the same time periods as measurements used for evaluation

• For all forms of mercury

Mercury Deposition Network (MDN)(wet deposition only)

Largest sources of total mercury emissions to the air in the U.S. and Canada, based on the U.S. EPA 1999 National Emissions Inventory

and 1995-2000 data from Environment Canada

Canaan Valley Institute-NOAA

BeltsvilleEPA-NOAA

Three NOAA sites committed to emerging inter-agency speciated mercury ambient concentration measurement network

(comparable to Mercury Deposition Network (MDN) for wet deposition, but for air concentrations)

Grand BayNOAA

1

Largest sources of total mercury emissions to the air in the U.S. and Canada, based on the U.S. EPA 1999 National Emissions Inventory

and 1995-2000 data from Environment Canada

Canaan Valley Institute-NOAACanaan Valley Institute-NOAA

BeltsvilleEPA-NOAABeltsville

EPA-NOAA

Three NOAA sites committed to emerging inter-agency speciated mercury ambient concentration measurement network

(comparable to Mercury Deposition Network (MDN) for wet deposition, but for air concentrations)

Grand BayNOAA

Grand BayNOAA

1

Air Concentration Network

Atmospheric MonitoringTo evaluate and improve atmospheric models, atmospheric monitoring must be:

• For air concentrations (not just wet deposition)

• For all forms of mercury

• For sites impacted by sources (not just background sites)

• At elevations in the atmosphere (not just at ground level)

?

Understanding and Decisions

?

?

Inflow/RunoffOutflow

Settling/Resusp Diffusion

Wet and dry Deposition

MeHg

Hg(0)

Hg(II)

Volatilization

Hg(II) MeHgBioaccumulation

BurialBurial


Source: R. Harris, Tetra-Tech, Inc.

Inflow/RunoffOutflow


Wet and dry Deposition

MeHg

Hg(0)

Hg(II)

Volatilization

Hg(II) MeHgBioaccumulation

BurialBurial


Source: R. Harris, Tetra-Tech, Inc.

Mercury in Lake Erie 45-cm Walleye (ug Hg / g)

0.0

0.2

0.4

0.6

0.8

1.0

1965

1970

1975

1980

1985

1990

1995

2000

2005

?

Source-attribution; Scenarios

Understanding Trends

Inputs for Ecosystem Models

Deposition For Entire Region

Incin

Manuf

Fuel (not coal electric)

Hg Dep to Lake Michigan (g/km2-yr)

Coal-electricCoal Scenarios

Why do we need atmospheric mercury models?

to get comprehensive source attribution information ...we don’t just want to know how much is depositing at any given location, we also want to know where it came from:

different source regions (local, regional, national, continental, global)different jurisdictions (different states and provinces) anthropogenic vs. natural emissionsdifferent anthropogenic source types (power plants, waste incin., etc)

to estimate deposition over large regions…because deposition fields are highly spatially variable, and one can’t measure everywhere all the time…

to estimate dry deposition... presently, dry deposition can only be estimated via models

to evaluate potential consequences of alternative future emissions scenarios

Atmospheric models can potentially provide valuable deposition and source-attribution information.

But… models have not been adequately evaluated, so we don’t really know very well how good or bad they are…

Challenges / critical data needs for model evaluation:

Ambient Monitoring Dataspeciated ambient concentrations at a number of different locations, both source-impacted and remote (need RGM and Hg(p), not just total gaseous mercury)

wet deposition

Emissions inventoriescomplete, accurate, speciatedup-to-date (or at least for the same period as measurements)temporal resolution better than annual (e.g., shut-downs, etc)

Atmospheric models can potentially provide valuable deposition and source-attribution information.

But… models have not been adequately evaluated, so we don’t really know very well how good or bad they are…

110

Hg from other sources: local, regional & more distant

emissions of Hg(0), Hg(II), Hg(p)

atmospheric depositionto the water

surface

Hg(0)

Hg(II) Hg(p)

atmosphericchemistry

inter-converts mercury forms

atmospheric deposition

to the watershed

Measurement of ambient air

concentrations

Measurement of wet

depositionWET DEPOSITION complex – hard to diagnoseweekly – many eventsbackground – also need near-field

AMBIENT AIR CONCENTRATIONS more fundamental – easier to diagnoseneed continuous – episodic source impactsneed speciation – at least RGM, Hg(p), Hg(0)need data at surface and above

many ways to get the “wrong” answer –incorrect emissions, incorrect transport, incorrect chemistry, incorrect 3-D precipitation, incorrect wet-deposition algorithms, etc..

models need ambient air concentrations first, and then if they can get those right, they can try to do wet deposition...

wet depmonitor

ambient air monitor

Wet deposition is a very complicated multi-stage phenomena...not ideal for atmospheric mercury model evaluation purposes

??

?

Ryaboshapko, A., et al.(2007). Intercomparison study of atmospheric mercury models: 1. Comparison of models with short-term measurements. Science of the Total Environment376: 228–240.

http://www.arl.noaa.gov/data/web/reports/cohen/49_EMEP_paper_2.pdf 112

EMEP Intercomparison Study of Numerical Models for Long-Range Atmospheric Transport of Mercury

BudgetsDry DepWet DepRGMHg(p)Hg0Chemistry

Conclu-sions

Stage IIIStage IIStage IIntro-duction

11

Total Gaseous Mercury (ng/m3) at Neuglobsow: June 26 – July 6, 1995

26-Jun 28-Jun 30-Jun 02-Jul 04-Jul 06-Jul01234 MEASURED

26-Jun 28-Jun 30-Jun 02-Jul 04-Jul 06-Jul01234 MSCE

26-Jun 28-Jun 30-Jun 02-Jul 04-Jul 06-Jul01234 CMAQ

26-Jun 28-Jun 30-Jun 02-Jul 04-Jul 06-Jul01234 GRAHM

26-Jun 28-Jun 30-Jun 02-Jul 04-Jul 06-Jul01234 EMAP

26-Jun 28-Jun 30-Jun 02-Jul 04-Jul 06-Jul01234 DEHM

26-Jun 28-Jun 30-Jun 02-Jul 04-Jul 06-Jul01234 ADOM

26-Jun 28-Jun 30-Jun 02-Jul 04-Jul 06-Jul01234 HYSPLIT



Conclu-sions


11

Total Particulate Mercury (pg/m3) at Neuglobsow, Nov 1-14, 1999

02-Nov 04-Nov 06-Nov 08-Nov 10-Nov 12-Nov 14-Nov0

50

100

150MEASURED


50

100

150CMAQ


50

100

150GRAHM


50

100

150EMAP


50

100

150DEHM


50

100

150ADOM


50

100

150HYSPLIT


50

100

150MSCE

11

MSCE Neuglobsow RGM

0

10

20

30

40

50

60

9 9 9 9 9 9 9 9 9 9 9 9 9 9

pg/m

3

ObsCalc

CMAQ Neuglobsow RGM

010203040506070

pg/m

3

ObsCalc

ADOM Neuglobsow RGM

010203040506070

pg/m

3

ObsCalc

EMAP Neuglobsow RGM

0

5

10

15

20

25

pg/m

3

ObsCalc

GRAHM Neuglobsow RGM

0

35

70

105

140

pg/m

3

ObsCalc

HYSPLIT Neuglobsow RGM

0

10

20

30

40

50

60

pg/m

3

ObsCalc



Conclu-sions


DEHM Neuglobsow RGM

0

6

12

18

24

30

pg/m

3

ObsCalc

Reactive Gaseous Mercury at Neuglobsow, Nov 1-14, 1999

Ryaboshapko, A., et al.(2007). Intercomparison study of atmospheric mercury models: 2. Modelling results vs. long-term observations and comparison of country deposition budgets. Science of the Total Environment 377: 319-333.

http://www.arl.noaa.gov/data/web/reports/cohen/49_EMEP_paper_2.pdf116

•• Three longThree long--term monitoring sites term monitoring sites –– Beltsville, Grand Bay, and CVI Beltsville, Grand Bay, and CVI ----measuring speciated ambient concentrations of mercury, related tmeasuring speciated ambient concentrations of mercury, related trace race species, and meteorological parameters form the core of an emergspecies, and meteorological parameters form the core of an emerging ing national ambient mercury measurement network.national ambient mercury measurement network.

•• The different sites provide the opportunity to investigate the eThe different sites provide the opportunity to investigate the effects of ffects of differences in regional source distribution, atmospheric processdifferences in regional source distribution, atmospheric processes, es, geographic characteristics, etc. on the fate and transport of atgeographic characteristics, etc. on the fate and transport of atmospheric mospheric mercury. However, additional sites are needed to provide a widermercury. However, additional sites are needed to provide a wider range of range of conditions.conditions.

•• Ancillary trace gas, aerosol, and meteorological measurements arAncillary trace gas, aerosol, and meteorological measurements are e critically needed to interpret mercury measurements.critically needed to interpret mercury measurements.

•• Substantial progress is being made on the development of StandaSubstantial progress is being made on the development of Standard rd Operating Procedures (SOP) and Best Measurement Practices (BMP) Operating Procedures (SOP) and Best Measurement Practices (BMP) , as , as well as QA/QC protocols.well as QA/QC protocols.

•• A draft SOP / BMP document will be discussed and ratified later A draft SOP / BMP document will be discussed and ratified later this this week at a meeting in Chicago week at a meeting in Chicago

Overall Summary

•• Initial backInitial back--trajectory analysis of peaktrajectory analysis of peak--measurement events suggest that measurement events suggest that concentrations at the sites are influenced episodically by localconcentrations at the sites are influenced episodically by local/regional /regional sources. sources.

•• Atmospheric mercury models are needed to provide sourceAtmospheric mercury models are needed to provide source--attribution attribution information and estimated impacts of alternative future scenarioinformation and estimated impacts of alternative future scenarios, but s, but models have not been adequately evaluated due to a lack of specimodels have not been adequately evaluated due to a lack of speciated ated ambient concentration data.ambient concentration data.

•• The emerging ambient monitoring network discussed today will proThe emerging ambient monitoring network discussed today will provide vide this critically needed measurement data. this critically needed measurement data.

•• With these data, models will be able to systematically evaluatedWith these data, models will be able to systematically evaluated ---- and and improved if necessary improved if necessary ---- allowing their results to be used with more allowing their results to be used with more confidence.confidence.

•• Moreover, the datasets will be available on an ongoing basis forMoreover, the datasets will be available on an ongoing basis for groundground--truthing model results generated for policy analysis purposes. truthing model results generated for policy analysis purposes.

Overall Summary... continued

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