measuring total reactive n and its...
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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