Assessment of SAPRC07 with updated isoprene chemistry against outdoor chamber experiments

Abstract

a b s t r a c tIsoprene, the most emitted non-methane hydrocarbon, is known to influence ozone (O 3 ) 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 O 3 . 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 O 3 than SAPRC07 for all experiments. In lower-NO x experiments, the new mechanism worsens O 3 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.

AtChem (version 1), an open-source box model for the Master Chemical Mechanism

“…Zero-dimensional box models have long been used to analyse ambient measurements and environmental chamber experiments. There is a natural mapping between a zero-170 R. Sommariva et al: The AtChem box model for the MCM dimensional box model and the static nature of a measurement site (Eisele et al, 1994;Carslaw et al, 1999;Emmerson et al, 2007;Elshorbany et al, 2009;Lu et al, 2012;Edwards et al, 2014;Brune et al, 2016;Whalley et al, 2016) and of an environmental chamber (Carter, 1995;Bloss et al, 2005a;Metzger et al, 2008;Chen et al, 2015;Novelli et al, 2018). With some modifications, the same modelling approach can also be used to analyse ship-based (Brauers et al, 2001;Sommariva et al, 2009Sommariva et al, , 2011a and aircraft-based (Chen et al, 2005;Ren et al, 2008;Sommariva et al, 2008Sommariva et al, , 2011b observations and to simulate the chemical evolution and photochemical processing of air masses (Derwent et al, 2003;Madronich, 2006;Roberts et al, 2007).…”

AtChem, an open source box-model for the Master Chemical Mechanism

“…Zero dimensional box-models have long been used to analyze ambient measurements and environmental chamber experiments. There is a natural mapping between a zero dimensional box-model and the static nature of a measurement site (Eisele et al, 1994;Carslaw et al, 1999;Emmerson et al, 2007;Elshorbany et al, 2009;Lu et al, 2012;Edwards et al, 2014;Brune et al, 2016;Whalley et al, 2016) and of an environmental chamber (Carter, 1995;Bloss et al, 2005a;Metzger et al, 2008;Chen et al, 2015;Novelli et al, 2018). With some modifications, the same modelling approach can also be used to analyze ship-based (Brauers et al, 2001;Sommariva et al, 2009Sommariva et al, , 2011a and aircraft-based (Chen et al, 2005;Ren et al, 2008;Sommariva et al, 2008Sommariva et al, , 2011b observations, and to simulate the chemical evolution and photochemical processing of air masses (Derwent et al, 2003;Madronich, 2006;Roberts et al, 2007)).…”