The seasonal characterization and source analysis of water-soluble inorganic ions in PM2.5 in Fuxin, northeast China

Abstract

In Fuxin, a few existing studies have illustrated the pollution characteristics of water-soluble ions (WSIIs) in PM2.5 in four seasons. To track the particulate pollution in Fuxin, sample filters of PM2.5 in the four seasons of spring, summer, autumn and winter in 2019 were collected. For the first time, the concentration and seasonal variation characteristics of PM2.5 and WSIIs were tested by gravimeter method and ion chromatography. Characteristics of WSIIs and their existence sources and forms were explored by ion balance calculation, correlation analysis and principal component analysis. The annual average concentrations of PM2.5 and WSIIs were (33.23 ± 13.03) μg·m−3 and (22.86 ± 9.62) μg·m−3, respectively. The seasonal WSIIs concentration followed the order: spring (29.98 μg·m−3) > autumn (28.85 μg·m−3) > winter (21.32 μg·m−3) > summer (11.28 μg·m−3). In WSIIs, 81.41% of them were secondary inorganic ions (SO4 2−, NO3 −, and NH4 +), contributed about 68.80% to PM2.5, and the chemical forms were mainly (NH4)2SO4 and NH4NO3. In this study, it has been revealed that PM2.5 samples exhibited acid properties in spring and autumn while, displayed alkalinity in summer and winter. The average value of NO3 −/SO4 2− was 0.67, so from these data it can be illustrated that fixed pollution sources were found to be dominant over mobile sources in Fuxin. The main identified sources of WSIIs in four seasons in Fuxin were sea salt particles and secondary particles, respectively. These results showed that the geographical factors of Bohai Bay and secondary transformation had a significant impact on the concentration of WSIIs of PM2.5 in Fuxin.