AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Formation and Gas-Particle Partitioning of Organic Nitrates: Influence on Ozone Production
LEA HILDEBRANDT RUIZ, Jeffrey Bean, Greg Yarwood, Bonyoung Koo, Uarporn Nopmongcol, University of Texas at Austin
Abstract Number: 297 Working Group: Aerosol Chemistry
Abstract In rural areas where emission rates of NOx (NO + NO2) are relatively low, ozone formation can be sensitive to secondary NOx sources such as decomposition of organic nitrates (R-ONO2). We present experimental evidence for NOx production when organic nitrates degrade by OH reaction and photolysis. Implementing NOx production from OH reaction with gas-phase organic nitrates in regional models causes ozone increases that are large enough to degrade model agreement with ozone observations. One potential explanation is that organic nitrates are less available to NOx recycling than gas-phase experiments suggest. We are investigating the hypothesis that uptake of organic nitrates into secondary organic aerosol (SOA) reduces the amount of NOx recycled by organic nitrate photolysis and OH reaction.
We added uptake of organic nitrates by SOA to the Comprehensive Air quality Model with extensions (CAMx). The conceptual model of Perraud et al. (PNAS 2012) was followed in which organic nitrate molecules stick to aerosol surfaces and become irreversibly buried by accretion of SOA. Initial modeling results were used to design laboratory chamber experiments in which organic nitrates were formed from the oxidation of VOCs in the presence of NOx and the distribution of organic nitrates between the gas and particle phases was measured. New chemical/physical mechanisms inferred from the experimental data were then tested by modeling the chamber experiments, and tested mechanisms were implemented in CAMx.