Isoprene chemistry in an urban area at the edge of the Ozarks: Observations from the SLAQRS campaign

Abstract:

We present field measurements of isoprene, its oxidation products, and an ensemble of other gas- and particle-phase measurements from the SLAQRS campaign during summer 2013 in Greater St. Louis. St. Louis lies near the ‘isoprene volcano’ in the Ozark Plateau, and oscillates between extremely high levels of isoprene and its oxidation products when winds are southerly, and low isoprene levels under northerly winds. During summer 2013 isoprene concentrations peaked at nearly 8 ppb, with the highest amounts occurring at night due to the associated transport time. In this presentation we interpret these measurements in terms of present understanding of isoprene chemistry, and examine their implications for daytime and nighttime chemistry in St. Louis. We pay particular attention to the measured abundance and variability of formic and acetic acids, and the relative importance of biogenic and anthropogenic precursors leading to their production.