Chemical composition, diurnal variation and sources of PM2.5 at two industrial sites of South China

Abstract

Diurnal PM2.5 samples were collected during summer and winter at an industrial complex site (site A) and an electronic waste (e–waste) recycling site (site B) in Qingyuan, South China. The concentration of organic carbon (OC), elemental carbon (EC), water soluble ions (WSI) and elements were investigated for their seasonal and diurnal variations. Organic matter (OM) was the most abundant specie in winter, accounting for 40.2% and 48.8% of PM2.5 in sites A and B, respectively; while in summer, excluding the elemental portion, WSI was the biggest part, which accounted for 37% and 49.4% of PM2.5 mass in sites A and B, respectively. Significantly higher concentrations were observed for most of the analyzed chemical species in winter. Average acidity of PM2.5 at both sites was significantly higher in summer. Diurnal variation with elevated concentrations of PM2.5 in nighttime samples was found at site B. Secondary inorganic aerosols (NH4+, NO3− and SO42−) exhibited clear day–to–night variation. Concentration of SO42− was about 15% higher in daytime samples. NH4+ and NO3− co–varied in winter, but were weakly associated with each other in summer. Sites A and B samples were almost all ammonium–rich in winter, whereas the summer samples were ammonium–poor during the daytime but ammonium–rich in the night. Positive matrix factorization (PMF) model analysis showed that secondary formation, biomass burning, regional industries, coal combustion and dust had significant contribution to PM2.5. Among them, secondary formation and biomass burning together contributed approximately 50% of PM2.5 mass at both sites. Additionally e–waste recycling activities resulted in high pollution of Cu at Site B.