Simulations of organic aerosol concentrations during springtime in the Guanzhong Basin, China

Tian Feng,Yichen Wang,Suixin Liu,Weijian Zhou,Zhenxing Shen,Guohui Li,Luisa T Molina,Naifang Bei,Xuexi Tie,Ting Zhang,Ru-Jin Huang,Junji Cao

doi:10.5194/acp-16-10045-2016

Abstract

Abstract. The organic aerosol (OA) concentration is simulated in the Guanzhong Basin, China from 23 to 25 April 2013 utilizing the WRF-CHEM model. Two approaches are used to predict OA concentrations: (1) a traditional secondary organic aerosol (SOA) module; (2) a non-traditional SOA module including the volatility basis-set modeling method in which primary organic aerosol (POA) is assumed to be semivolatile and photochemically reactive. Generally, the spatial patterns and temporal variations of the calculated hourly near-surface ozone and fine particle matters agree well with the observations in Xi'an and surrounding areas. The model also yields reasonable distributions of daily PM2.5 and elemental carbon (EC) compared to the filter measurements at 29 sites in the basin. Filter-measured organic carbon (OC) and EC are used to evaluate OA, POA, and SOA using the OC ∕ EC ratio approach. Compared with the traditional SOA module, the non-traditional module significantly improves SOA simulations and explains about 88 % of the observed SOA concentration. Oxidation and partitioning of POA treated as semivolatile constitute the most important pathway for the SOA formation, contributing more than 75 % of the SOA concentrations in the basin. Residential emissions are the dominant anthropogenic OA source, constituting about 50 % of OA concentrations in urban and rural areas and 30 % in the background area. The OA contribution from transportation emissions decreases from 25 % in urban areas to 20 % in the background area, and the industry emission OA contribution is less than 6 %.

Highlights

Atmospheric aerosol or fine particulate matter (PM2.5) influences regional and global climate directly by absorbing and scattering the solar radiation and indirectly by serving as cloud condensation nuclei (CCN) and ice nuclei (IN) to modify cloud properties (Seinfeld and Pandis, 2006)
primary organic aerosol (POA) is emitted into the atmosphere directly, while secondary organic aerosol (SOA) forms through chemical reactions of precursors in the atmosphere
The objective of the present study is to examine the formation and source apportionments of Organic aerosol (OA) and SOA in Guanzhong Basin (GZB) during 3 days in the spring of 2013 using the WRF-CHEM model

Summary

Introduction

Atmospheric aerosol or fine particulate matter (PM2.5) influences regional and global climate directly by absorbing and scattering the solar radiation and indirectly by serving as cloud condensation nuclei (CCN) and ice nuclei (IN) to modify cloud properties (Seinfeld and Pandis, 2006). Elevated aerosol concentrations exert adverse impacts on ecosystems and human health, and reduce the visibility of the atmosphere to cause the haze formation, impairing air quality (Cao et al, 2012a, b; Greenwald et al, 2006; Seinfeld and Pandis, 2006). OA is categorized into primary and secondary OAs on the basis of its source and/or formation, referred to as POA and SOA, respectively. POA is emitted into the atmosphere directly, while SOA forms through chemical reactions of precursors in the atmosphere. Volatile organic compounds (VOCs) emitted from anthropogenic or biogenic sources undergo a series of oxidation and gas–particle partitioning to yield SOA, Published by Copernicus Publications on behalf of the European Geosciences Union

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