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A Tale of Two Extremes: Contrasting NH 3 at the Bakersfield and Pasadena Supersites Jennifer Murphy Milos Markovic Trevor VandenBoer Raluca Ellis Department.

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Presentation on theme: "A Tale of Two Extremes: Contrasting NH 3 at the Bakersfield and Pasadena Supersites Jennifer Murphy Milos Markovic Trevor VandenBoer Raluca Ellis Department."— Presentation transcript:

1 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

2 Ammonia and Particle Formation NO x SO 2 NH 3 HNO 3 H 2 SO 4 (NH 4 ) 2 SO 4 NH 4 NO 3 Highly coupled and non-linear

3 Historical CARB data seasonality in NH 4 NO 3 seasonality in (NH 4 ) 2 SO 4

4 Clarisse et al., JGR, 2010 IASI retrieval of atmospheric ammonia Mar – Oct average at 700 m during morning orbit (09:30 local) NH 3 in the San Joaquin Valley Fresno Bakersfield Visalia NH 3 (ppb) TM5 model prediction

5 Mobile Emissions of NH 3 Bishop et al., ES&T, 2010 Mobile emissions of NH 3 comparable to NO x in new, aggressively driven, vehicles

6 AIM-IC in Bakersfield A – PM 2.5 impactor B – membrane denuder C – particle collection chamber D – ion chromatographs Hourly gas and PM 2.5 measurements of SO 4 2-, NO 3 -, Cl -, Br -, NO 2 -, organic acids NH 4 +, K +, Na +, Mg 2+, Ca 2+, amines

7 QC-TILDAS in Pasadena Ellis et al., Atmos Meas Tech, 2010 Fast (1Hz) measurements of gas phase NH 3 with minimal sampling artefacts

8 Ammonia Time Series Bakersfield Pasadena hourly averages

9 Diurnal Profiles of NH x Partitioning Ammonia is controlled by emissions and dilution Ammonia is controlled by partitioning and transport AMS data from Jimenez group, CU

10 Temperature and NH 3 at Bakersfield Overnight Temperature (K) Daily Maximum Ammonia (ppb)

11 Comparison with Model CMAQ data courtesy of Kirk Baker, US EPA

12 Model usually has a low bias for NH 3 Model usually has a high bias for HNO 3 Model overestimates NH 4 NO 3

13 Historical Record at Bakersfield Partitioning can account for winter NH 4 +, but not NO 3 -

14 Summary NH x is ~4 times larger at Bakersfield than at Pasadena different processes control NH 3 at the two ground sites CMAQ does not represent Bakersfield NH 3 well (emissions or partitioning) Additional Questions aerosol pH influence of/on organic acids relative contributions of NH 3 emissions sources

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17 FREE AMMONIA, FA = TA – 2 * TS = [NH 4 + ] + [NH 3(g) ] – 2 * [SO 4 2- ] Particle Fraction Markovic et al., Atmos. Chem. Phys., 2011 Ohio Valley predict partitioning using ISORROPIA

18 Conditions: RH = 40 %, T = 275 – 315 K, TN = 20 nmol m -3, TS = 21 nmol m -3, TA = nmol m -3 FA values during the campaign = ( -42 nmol m -3 to 2750 nmol m -3 ) Nitrate partitioning driven mainly by meteorology High NH 3, low TS and TN Particle Fraction

19 Pasadena data on chemical map generated assuming TN = 100 nmol m -3 TN actually ranges from 10 – 700 and correlates with FA


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