a tale of two extremes: contrasting nh 3 at the bakersfield and pasadena supersites
DESCRIPTION
A Tale of Two Extremes: Contrasting NH 3 at the Bakersfield and Pasadena Supersites. Jennifer Murphy Milos Markovic Trevor VandenBoer Raluca Ellis Department of Chemistry University of Toronto. Ammonia and Particle Formation. Highly coupled and non-linear. H 2 SO 4. HNO 3. - PowerPoint PPT PresentationTRANSCRIPT
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A Tale of Two Extremes: Contrasting NH3 at the Bakersfield and Pasadena Supersites
Jennifer MurphyMilos Markovic
Trevor VandenBoerRaluca Ellis
Department of ChemistryUniversity of Toronto
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Ammonia and Particle Formation
NOxSO2NH3
HNO3H2SO4(NH4)2SO4NH4NO3
Highly coupled and non-linear
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Historical CARB data
seasonality in NH4NO3
seasonality in (NH4)2SO4
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Clarisse et al., JGR, 2010
IASI retrieval of atmospheric ammoniaMar – Oct average at 700 m during morning orbit (09:30 local)
NH3 in the San Joaquin Valley
Fresno
Bakersfield
Visalia
NH
3 (ppb)
TM5 model prediction
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Mobile Emissions of NH3
Bishop et al., ES&T, 2010Mobile emissions of NH3 comparable to NOx in new, aggressively driven, vehicles
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AIM-IC in Bakersfield
A – PM2.5 impactorB – membrane denuderC – particle collection chamberD – ion chromatographs
Hourly gas and PM2.5 measurements of SO4
2-, NO3-, Cl-, Br-, NO2
-, organic acids NH4
+, K+, Na+, Mg2+, Ca2+, amines
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QC-TILDAS in Pasadena
Ellis et al., Atmos Meas Tech, 2010
Fast (1Hz) measurements of gas phase NH3 with minimal sampling artefacts
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Ammonia Time SeriesBakersfield
Pasadenahourly averages
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Diurnal Profiles of NHx Partitioning
Ammonia is controlled by emissions and dilution
Ammonia is controlled by partitioning and transport
AMS data from Jimenez group, CU
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Temperature and NH3 at Bakersfield
Overnight Temperature (K)
Dai
ly M
axim
um A
mm
onia
(ppb
)
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Comparison with Model
CMAQ data courtesy of Kirk Baker, US EPA
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Model usually has a low bias for NH3
Model usually has a high bias for HNO3
Model overestimates NH4NO3
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Historical Record at Bakersfield
Partitioning can account for winter NH4
+, but not NO3-
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Summary
• NHx is ~4 times larger at Bakersfield than at Pasadena
• different processes control NH3 at the two ground sites
• CMAQ does not represent Bakersfield NH3 well(emissions or partitioning)
Additional Questions
• aerosol pH
• influence of/on organic acids
• relative contributions of NH3 emissions sources
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FREE AMMONIA, FA = TA – 2 * TS= [NH4
+] + [NH3(g)] – 2 * [SO42-]
Particle FractionMarkovic et al., Atmos. Chem. Phys., 2011
Ohio Valley
predict partitioning using ISORROPIA
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Conditions:RH = 40 %, T = 275 – 315 K, TN = 20 nmol m-3 , TS = 21 nmol m-3 , TA = 0 - 2750 nmol m-3
FA values during the campaign = ( -42 nmol m-3 to 2750 nmol m-3 )
Nitrate partitioning driven mainly by meteorologyHigh NH3, low TS and TN
100 80 60 40 20 0 Particle Fraction
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Particle Fraction
310
300
290
280
270
260
3002001000-100-200x10-9
Pasadena data on chemical map generated assuming TN = 100 nmol m-3
TN actually ranges from 10 – 700 and correlates with FA