Articles | Volume 16, issue 15
Research article
09 Aug 2016
Research article |  | 09 Aug 2016

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

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

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 %.

Short summary
The springtime organic aerosol (OA) concentrations in the Guanzhong Basin, China are simulated using the WRF-Chem model with two secondary OA (SOA) modules. Model results are verified with near-surface observations. The non-traditional SOA module significantly improves SOA simulation. Oxidation and partitioning of primary OAs is the most important pathway in SOA formation. Residential emissions are the dominant anthropogenic OA source.
Final-revised paper