Importance of biogenic volatile organic compounds to acyl peroxy nitrates (APN) production in the southeastern US during SOAS 2013

Gas-phase atmospheric concentrations of peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN), and peroxymethacryloyl nitrate (MPAN) were measured on the ground using a gas chromatograph electron capture detector (GC-ECD) during the Southern Oxidants and Aerosols Study (SOAS) 2013 campaign (1 June to 15 July 2013) in Centreville, Alabama, in order to study biosphere-Atmosphere interactions. Average levels of PAN, PPN, and MPAN were 169, 5, and 9&pptv, respectively, and the sum accounts for an average of 16&% of <span classCombining double low line"inline-formula">NOy</span> during the daytime (10:00 to 16:00 local time). Higher concentrations were seen on average in air that came to the site from the urban <span classCombining double low line"inline-formula">NOx</span> sources to the north. PAN levels were the lowest observed in ground measurements over the past two decades in the southeastern US. A multiple regression analysis indicates that biogenic volatile organic compounds (VOCs) account for 66&% of PAN formation during this study. Comparison of this value with a 0-D model simulation of peroxyacetyl radical production indicates that at least 50&% of PAN formation is due to isoprene oxidation. MPAN has a statistical correlation with isoprene hydroxynitrates (IN). Organic aerosol mass increases with gas-phase MPAN and IN concentrations, but the mass of organic nitrates in particles is largely unrelated to MPAN.