Seasonal characteristics of PM2.5 and its chemical species in the northern rural China

Abstract Daily PM2.5 samples were collected at a rural site in North China for four consecutive seasons from summer of 2015 to spring of 2016. Results revealed that the studied rural area suffered from severe PM2.5 pollution with its annual average concentration of 109.6 ± 45.0 μg m−3, which was about 3.1 times higher than the national air quality standard of China. Among all identified species, water soluble inorganic ions (WSIIs) were the major component, accounting for 46.0 ± 11.1% of PM2.5 mass. The sum of element carbon (EC) and organic carbon (OC) accounting for 24.1 ± 11.5%. The trace elements accounted for about only 2% of PM2.5 mass. The results of the chemical mass balance of PM2.5 showed that 74–99% of the PM2.5 mass can be reconstructed by the identified species. SNA (the sum of SO42−, NO3− and NH4+) and particulate organic matter (POM) were evident two kinds of predominant components of the PM2.5, which together accounted for ~60%, with seasonal variations. Mineral dust and EC accounted for ~8% and ~7%, respectively. The trace element oxide (TEO), biomass burning-derived K+ and coal combustion-derived Cl− together represented about 10%. Strong variations of PM2.5 and its species above on a timescale of seasons indicated that the local sources, such as coal combustion and biomass burning, dominated the local atmospheric pollutants.