Abstract. 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 NOy 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 NOx 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.
Degradation of volatile organic compounds in the gas phase by heterogeneous photocatalysis with titanium dioxide/ultraviolet light
