Abstract
Abstract. A new method is proposed to simplify complex atmospheric chemistry reaction schemes, while preserving SOA formation properties, using genetic algorithms. The method is first applied in this study to the gas-phase α-pinene oxidation scheme. The simple unified volatility-based scheme (SUVS) reflects the multi-generation evolution of chemical species from a near-explicit master chemical mechanism (MCM) and, at the same time, uses the volatility-basis set speciation for condensable products. The SUVS also unifies reactions between SOA precursors with different oxidants under different atmospheric conditions. A total of 412 unknown parameters (product yields of parameterized products, reaction rates, etc.) from the SUVS are estimated by using genetic algorithms operating on the detailed mechanism. The number of organic species was reduced from 310 in the detailed mechanism to 31 in the SUVS. Output species profiles, obtained from the original subset of the MCM reaction scheme for α-pinene oxidation, are reproduced with maximum fractional error at 0.10 for scenarios under a wide range of ambient HC/NOx conditions. Ultimately, the same SUVS with updated parameters could be used to describe the SOA formation from different precursors.
Highlights
Aerosols play an important role in atmospheric chemistry, with impacts on local, regional and global air quality and human health exposure
Organic aerosols are classified as primary organic aerosols (POA) and secondary organic aerosols (SOA)
The SOA is formed via gas/particle transfer (Pankow, 1994) or heterogeneous reactions (Jang et al, 2002; Tolocka et al, 2004; Kalberer et al, 2004; Liggio et al, 2005) of the organic products from the atmospheric oxidation of biogenic and/or anthropogenic volatile organic compounds (VOCs)
Summary
Aerosols play an important role in atmospheric chemistry, with impacts on local, regional and global air quality and human health exposure. The first approach is a two-product gas/particle partitioning model (Odum et al, 1996), in which two surrogate species are used to describe hundreds of oxidation products from each VOC precursor In this model, two parameters for mass-based stoichiometric yields (α1 and α2) and two for partitioning coefficients (Kp, and Kp,2) are obtained by least square fitting of smog chamber measurements. Two parameters for mass-based stoichiometric yields (α1 and α2) and two for partitioning coefficients (Kp, and Kp,2) are obtained by least square fitting of smog chamber measurements In this empirical model, the two surrogate products in the gas phase are described by a one-step chemical reaction. As a first step to explore the new chemical reaction scheme and fitting method, we focus our study on atmospheric gas phase reactions only
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