Biomass burning and aqueous reactions drive the elevation of wintertime PM2.5 in the rural area of the Sichuan basin, China

Abstract

This study conducted a field campaign using a time-of-flight aerosol chemical speciation monitor (ToF-ACSM) for PM2.5 measurement at a rural site in Sichuan Basin (SCB) during winter. The composition, diurnal variation, and source apportionment of non-refractory PM2.5 were analyzed. During the whole sampling process, the average concentration of PM2.5 was 52.9 μg m−3, in which the organic aerosol (OA) concentration was the highest (25.5 μg m−3), followed by nitrate (11.1 μg m−3), sulfate (8.2 μg m−3), ammonium (6.9 μg m−3) and chloride (1.3 μg m−3). The positive matrix factorization (PMF) model was used to analyze the sources of OA. Five factors, including a hydrocarbon-like organic aerosol (HOA), a coal combustion organic aerosol (CCOA), a biomass burning organic aerosol (BBOA), a less oxidized oxygenated organic aerosol (LO-OOA), and a more oxidized oxygenated organic aerosols (MO-OOA), were resolved. A haze episode was identified whose evolution was found to be mainly driven by BBOA. The backward trajectory and potential source contribution function (PSCF) analysis showed that the regions over northern Chongqing and eastern Sichuan province were potential source regions of BBOA and CCOA. This study can increase our knowledge of PM2.5 characteristics and sources, providing an understanding of the interaction between anthropogenic and natural emissions and atmospheric aging during transport in SCB.