Ozone Production in the Southern San Joaquin Valley: A NOx Perspective

We present measurements of NO2, total alkyl nitrates (ΣANs), and HNO3 by thermal dissociation-laser induced fluorescence (TD-LIF) and NO by chemiluminescence made as part of CalNex-2010 at the San Joaquin Valley supersite in Bakersfield, California (May 15-June 28). We discuss these nitrogen oxide observations in the context of co-located OH, HO2, HONO, H2CO, H2O2, VOC, and O3 measurements, examining the instantaneous ozone production rate (PO3) as a function of NO concentration and HOx production rate. Furthermore, using the slope of the Ox/ΣANs correlation, we report the lowest ever observed urban ΣANs branching ratio (1.5-2%). We test our understanding of this chemistry with a photochemical model, evaluating the implications of suppressed alkyl nitrate formation on O3 production.