measuring total reactive n and its...

Measuring Total Reactive N and its Composition

• Bret A. Schichtel1, Katie Benedict2, Christian M. Carrico2 , Anthony Prenni2, Jr.2, Ezra Levin2, Derek Day3, Doris Chen2, John Ray1, William C. Malm3, Jeffrey L. Collett2,

Sonia M. Kreidenweis2

1National Park Service, CSU/CIRA, Fort Collins, Colorado 805232Department of Atmospheric Science, Colorado State University

3Cooperative Institute for Research in the Atmosphere (CIRA), CSU

Measuring Total Chemically Reactive N• TCRN = NOy + NHx

(Oxidized) (Reduced)• NOy ≡ NO + NO2 + NO3 + 2xN2O5 + HNO3 + HONO + HO2NO2 +

R-ONO2 (organic nitrates such as PAN and alkyl nitrates) +R-ONO (organic nitrites) +NO3- (particulate nitrate).

• NHx = NH3 + NH4 + amines (R-NHx)other reduced organic molecules

• Everything but N2O and N2

Reactive N Measurement Needs• Ecosystem health

• Total reactive N deposition at weekly-monthly scales• Assess critical loads (target loads?)• Track status and trends of Nr inputs to ecosystems

• Reactive N Management• Speciated organic and inorganic Nr deposition with 24-h

or less duration• Attribution of each species to its emission source (control

measures)• Assessment of other effects: SOx/NOx NAAQS, ozone, visibility,

human health, …

Current Monitoring Networks Issues• Important species are not measured• Accuracy with which some species are measured• Time scale of measurement (weekly is long for source attribution, models)

• Spatial representation of CASTNET is poor• network distribution is uneven• deposition data can’t be spatially interpolated

• Deposition is not measured but estimated and only at one location

Species of interest• Measured

• Dry: HNO3, particle NO3 and NH4• Wet: NO3

-, NH4+

• Missing• Dry Species

• NH3• NOx (NO and NO2) • Reduced organic gases (Aliphatic amines …..)• Oxidized organic gases (PAN - alkyl nitrates …)• Reduced and oxidized organic nitrogen containing particulates

• Wet Species• Oxidized and reduced organic compounds• All occult deposition

Why the Missing Components Matter Total Deposition Budget (Spring)

20%

20%

26%

7%

10%

4%

9% 1% 3%

Wet ON

Wet NH4

Wet NO3

NOx

NH3

HNO3

ON (estimated)

Dry Deposition (Spring)

NH337%

NOx13%

NO34%

NH412%

ON Gas/particles(estimated) 34%

NH3NOxON Gas/particlesNO3NH4

Missing

Measured

WetDry

ROMANS data

?

Total Water Soluble Particulate Organic nitrogen

• WSON = TN – (NO2‐ + NO3

‐ + NH4+)

• Total water soluble N• Shimadzu TOC VCSH total organic carbon analyzer with a total nitrogen module

• NO2‐, NO3

‐, NH4+

• ion chromatography • Individual organic nitrogen compounds• Liquid Chromatography with Time of Flight Mass Spectrometry using electrospray ionization

PM2.5 Hivol samplers

Benedict et al., 2011

Total Water Soluble Particulate Organic N and Biomass Burning Markers at ROMO

Benedict et al., 2011

NH3 = TNx – Nox: TNx contains reduced organic and other compounds

Teledyne NH3 Chemiluminescent Analyzer

Teledyne Instrument Sensitivity to Non-NH3 Gas Species (Permeation Tube Lab Tests)

Fractional Sensitivity of Instrument*Importance Chemiluminescence Ion Mobility Cavity Ring Down

Acetaldehyde Biogenic Chemiluminescent Compound [Marley and 0.4% 0.1% -0.1%

Acetonitrile 1 Biomass Burning Emissions 77.6% 0.2% 1.1%

Acetonitrile 2 [Yokelson et al., 2009] 63.1% 0.0% -0.2%

Alpha-Pinene Biogenic Emissions (Coniferous) 0.9% 0.0% -0.1%

Isoprene Biogenic Emissions (Deciduous) 3.5% 0.2% 0.9%

Methylamine 1 Primary Amine 69.2% 77.0% 5.5%

Methylamine 2 Ammonia-like, Particle and Gas phase 74.2% 84.8% 3.2%

Methylamine 3 [Ge et al., 2011] 86.8% 84.9% 5.6%

*using a 67 ppb input concentration generated with a permeation tubeSensitivity: Negligible Slight High

Ambient Urban Air with NH3Denuder In-line

-1

0

1

2

3

4

5

6

7

8

0:00 6:00 12:00 18:00 0:00

NH

3C

once

ntra

tion (

ppb)

ChemiluminescenceCavity Ring DownIon Mobility

Zero Air

Chemiluminescence clearly has some non-NH3 interferences

TNx – NOy – NH3

Boulder, CO Smoke Impacts

Estimate of Reduced Organic N Gas

Total gaseous reduced N + Artifacts

Smoke Impact

Reduced N at Targhee, WY (Grand Teton) - 1 hr avg

Smoke event

“Reduced” organic N

NH3

Ammonia + CO (1 hr avg)

Modified IMPROVE Samplers to Collect Reduced Nitrogen

Phosphoric acid impregnated cellulose backup filter to collect NH3 and volatilized NH3 from nylasorb filters

Acid impregnated cellulose front filter to collect NH3 + NH4+ and other

gases e.g. methylamine

IMPROVE samplers collects 24-h samples

Filters analyzed for NH4

+ and methylamine by ion chromatography

Measurement Quality

Good agreement vs. URG denuder + filter-pack

Good precision

IMPROVE NHx and Methylamine Monitoring Sites June 2011-June 2012

Using IMPROVE infrastructure: Site operators, RTI performing IC analysisCSU (Collett et al.,) is coordinating monitoring, QA/QC, data reduction, filter prep

Pilot IMPROVE NHx network – 2011 Obs

• Seasonal cycle apparent at all sites

• Highest concentrations at eastern and southern sites

• NH4+ from

IMPROVE Module B filter will help constrain gas/particle split

A first look: monthly average NHx (1-in-3 day sampling)

Missing Nr Components Measurements• Routine or semi-routine methods to measure

• Total wet organic N • Dry NH3

• Soluble particulate organic N• NO / NO2 / gaseous oxidized organic N

• Research• Oxidized and reduced wet organic N• Reduced gas and particle organic N • ON marker species useable in receptor models

Some Possible Next Steps

• Determine which of the non-measured N species contribute significantly to Nr deposition

• Develop the tools to measure these compounds suitable for routine monitoring in remote locations

• Assess where these N species come from and if appropriate develop emission control strategies