Atmos. Chem. Phys. Discuss., 12, 5189-5223, 2012
www.atmos-chem-phys-discuss.net/12/5189/2012/
doi:10.5194/acpd-12-5189-2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Model evaluation of NO3 secondary organic aerosol (SOA) source and heterogeneous organic aerosol (OA) sink in the Western United States
J. L. Fry and K. Sackinger
Department of Chemistry, Reed College, Portland, OR, USA

Abstract. The relative importance of NO3-initiated source and heterogeneous sink of organic aerosol in the Western United States is investigated using the WRF/Chem regional weather and chemistry model. The model is run for the four individual months, representing the four seasons, of January, May, August, and October, to produce hourly spatial maps of surface concentrations of NO3, organic aerosol (OA), and reactive organic gases (ROG, a sum of alkene species tracked in the lumped chemical mechanism employed). These "baseline" simulations are used in conjunction with literature data on secondary organic aerosol (SOA) mass yields, average organic aerosol composition, and reactive uptake coefficients for NO3 on organic surfaces to predict SOA source and OA heterogeneous loss rates due to reactions initiated by NO3. We find both source and sink rates maximized downwind of urban centers, therefore with a varying location that depends on wind direction. Both source and sink terms are maximum in summer, and SOA source dominates over OA loss by approximately three orders of magnitude, with large day-to-day variability. The NO3 source of SOA is found to be atmospherically significant (peak production rates of 0.4–3.0 μg kg−1 h−1), while the heterogeneous sink of OA via NO3 surface reactions (peak loss rates of 0.11–2.3 × 10−3 μg kg−1 h−1) is likely too small to significantly impact the atmospheric lifetime of either organic aerosol or oxidized nitrogen (NOy).

Citation: Fry, J. L. and Sackinger, K.: Model evaluation of NO3 secondary organic aerosol (SOA) source and heterogeneous organic aerosol (OA) sink in the Western United States, Atmos. Chem. Phys. Discuss., 12, 5189-5223, doi:10.5194/acpd-12-5189-2012, 2012.
 
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