Predicting SOA from organic nitrates in the southeastern United States

Monday, 14 December 2015
Poster Hall (Moscone South)
Havala Pye1, Deborah Luecken2, Lu Xu3, Christopher Boyd3, Nga Lee Ng3, Kirk R Baker4, Benjamin R Ayres5, Jesse O Bash6, Karsten Baumann7, William P. L. Carter8, Eric S Edgerton9, Juliane Fry10, William T Hutzell11, Donna B Schwede12 and Paul B Shepson13, (1)US EPA, Durham, United States, (2)U.S. EPA, RTP, NC, United States, (3)Georgia Institute of Technology Main Campus, Atlanta, GA, United States, (4)Environmental Protection Agency Research Triangle Park, Research Triangle Park, NC, United States, (5)Reed College, Portland, OR, United States, (6)U.S. EPA, NERL, RTP, NC, United States, (7)Atmospheric Research and Analysis, Morrisville, NC, United States, (8)University of California Riverside, Riverside, CA, United States, (9)Atmospheric Research & Analysis, Inc., Cary, NC, United States, (10)Reed College, Dept. of Chemistry, Portland, OR, United States, (11)US EPA, RTP, NC, United States, (12)Environmental Protection Agency Research Triangle Park, Durham, NC, United States, (13)Purdue University, West Lafayette, IN, United States
Organic nitrates have been identified as an important component of ambient aerosol in the Southeast United States. In this work, we use the Community Multiscale Air Quality (CMAQ) model to explore the relationship between gas-phase production of organic nitrates and their subsequent aerosol-phase partitioning for the Southern Oxidants and Aerosol Study (SOAS) 2013 time period.

Current chemical transport models may underestimate the role of particulate organic nitrates (pON), and aerosol parameterizations are generally not connected to later generation gas-phase species. Explicit predictions of pON from gas-phase intermediates is challenging as gas-phase mechanisms need verification. We highlight areas where further information is needed. During the morning and evening transition hours, reactions of monoterpenes with ozone, OH, and nitrate radicals are predicted to contribute to organic nitrate formation. During the night, organic nitrate formation is primarily due to nitrate radicals and RO2+HO2 reactions with high yields of organic nitrates, above what has been observed in many chamber experiments. We find that the CMAQ model overestimates total gas-phase alkyl nitrates, particularly at night, and that uptake to the particle followed by hydrolysis can improve model predictions of both the gas and aerosol phase components.