Comparative analysis of the chemical characteristics and sources of fine atmospheric particulate matter (PM2.5) at two sites in Changzhou, China

Abstract

In this study, PM2.5 and its chemical components were compared at an industrial site and a suburban site in Changzhou, China, during the winter of 2016. The average PM2.5 concentration was higher at the industrial site (113.06 ± 64.74 μg/m3) than that at the suburban site (84.75 ± 41.76 μg/m3), which suggests that severe pollution with higher emissions occurred in the industrial region. The ion balance indicated that PM2.5 was weakly acidic and neutral at the suburban and industrial sites, respectively. Water-soluble inorganic ions (WSIIs) were the largest contributor to PM2.5 (suburban 49.8% vs. industrial 36.0%), and carbonaceous components comprised a significant fraction (approximately 30%) of ambient PM2.5. Correlations between water-soluble organic carbon (WSOC) and eight carbon fractions showed secondary formation, and biomass burning had a significant impact on the carbonaceous species. The nitrogen and sulfur oxidation ratios exceeded 0.10, which further implied the likelihood of secondary transformation. Thirteen elements comprised ~3.0% of the PM2.5 mass at both sites.Soot-particle aerosol mass spectrometry (SP-AMS) coupling positive matrix factorization (PMF) was used to characterize the chemical composition and evaluate the sources of water-soluble organic aerosols (WSOA). The results showed that the WSOA originated from three sources. The PMF model identified six sources of PM2.5, including secondary aerosols, biomass burning, traffic, soil dust, coal combustion, and road dust (industrial emissions), with mass contributions of 45.1% (38.3%), 18.7% (14.0%), 6.4% (15.9%), 13.8% (8.7%), 7.3% (13.3%), and 8.7% (9.6%) at the suburban (industrial) site. To the best of our knowledge, this is the first study to comprehensively study the chemical characteristics and source apportionment of PM2.5 in suburban/industrial regions.