Seasonal variation of water-soluble inorganic ions and carbonaceous components of PM2.5 and PM1 in industrial and residential areas of Suizhou, China

Abstract

Seasonal variations of fine particulate matter (PM) and its chemical components in Suizhou are investigated by collecting PM_2.5 and PM₁ samples from industrial and residential areas between March 2017 and February 2018. The findings reveal more severe PM pollution in industrial areas compared to residential areas. Concentrations and percentages of water-soluble inorganic ions (WSII) in PM are higher in spring and winter. Notably, the high levels of SO₄²⁻ and NO₃⁻ in PM_1-2.5 indicate that secondary transformation of SO₂ and NO_x significantly contribute to the rapid increase in PM_1-2.5. The conversion of NO₂ to NO₃⁻ is a key factor in the winter increase of mass concentrations of PM_2.5 [ρ(PM_2.5)], while photochemical reactions involving NO₂ drive the summer increase of ρ(PM_2.5). Organic carbon (OC) and elemental carbon (EC) are mainly distributed in PM₁, with OC peaking in winter. Chemical fractionation of PM reveals that carbonaceous components have a greater impact on PM₁ concentration than WSII, whereas WSII more significantly affects ρ(PM_2.5) than carbonaceous components. The OC to EC ratio in industrial areas (2.5 ± 1.4) and residential areas (1.9 ± 0.8) suggests more prominent secondary aerosol pollution in industrial areas. Significant correlations between secondary organic carbon (SOC), SOC conversion rate (η_SOC), and concentrations of O₃-8h and NO₂ in Suizhou further indicate that O₃ and NO₂ levels in the atmosphere influence the generation of SOC and η_SOC.