Assessment of SAPRC07 with updated isoprene chemistry against outdoor chamber experiments. (March 2015)

• Record Type: Journal Article
• Authors: Chen, Yuzhi; Sexton, Kenneth G.; Jerry, Roger E.; Surratt, Jason D.; Vizuete, William
• Is Part Of: Atmospheric environment. Volume 105(2015)
• Page Start: 109
• Page End: 120
• Publication Date: 2015-03
• Subjects: Atmospheric chemical mechanism -- Isoprene -- Smog chamber -- SAPRC07; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2015.01.042
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: Isoprene, the most emitted non-methane hydrocarbon, is known to influence ozone (O3 ) formation in urban areas rich with biogenic emissions. To keep up with the recent advance on isoprene oxidation chemistry including the identification of isoprene epoxydiols (IEPOX) as a precursor to secondary organic aerosol (SOA), Xie et al. (2013) updated the SAPRC (Statewide Air Pollution Research Center)-07 chemical mechanism. It is currently unknown how the Xie modification of SAPRC07 impacts the ability of the model to predict O3 . In this study we will evaluate the Xie mechanism with simulations of 24 isoprene experiments from the UNC Dual Gas-phase Chamber. Our results suggest that the new mechanism increases NO x (nitrogen oxides) inter-conversion and produces more O3 than SAPRC07 for all experiments. In lower-NO x experiments, the new mechanism worsens O3 performance in the wrong direction, increasing bias from 4.92% to 9.44%. We found increased NO x recycling from PANs accounts for that. This could be explained by more PANs made due to increased first generation volatile organic compound (VOC) products and hydroxyl radical (OH) production. Highlights: We evaluated the updated CMAQ version of SAPRC07 against chamber experiments. The mechanism shortens NO to NO2 conversion time and increases O3 production. In lower-NOX conditions the mechanism increases the bias of O3 from 4.9% to 9.4%. New Chemistry increases the reaction rate of VOCs and enhances radical production.