Characterization of the size-segregated inorganic compounds in Lin'an, a Regional Atmosphere Background Station in the Yangtze River Delta region

PM1.0 and PM2.5 samples are collected in Lin'an, a Regional Atmosphere Background Station in spring (1–30 April), summer (1–31 July), autumn (1–31 October) and winter (1–31 January) in 2011 to investigate the seasonal characteristics of aerosol pollution in the Yangtze River Delta region. The daily concentrations of water-soluble ions are 24.6 ± 12.0 μg m−3 and 36.6 ± 23.6 μg m−3 in PM1.0 and PM2.5, respectively. SO42−SO42−, NO3−NO3− and NH4+NH4+ are the dominant contributors of water-soluble ions, accounting for 78.6% (spring), 83.5% (summer), 80.6% (autumn) and 81.9% (winter) of the total ions measured in PM1.0 and 80.2% (spring), 85.4% (summer), 78.9% (autumn) and 78.9% (winter) in PM2.5. Seasonal variation is observed, with the lowest ions concentration in winter and the highest one in summer. Nevertheless, the crustal elements (e.g., Ca, Mg, Al, Fe, etc.) have the highest concentrations in spring. Most of the pollution species (Sb, Se, Cd, Pb, As and Zn) have enrichment factor values higher than 100, implying a strong possibility that the air pollution originates from anthropogenic sources and have no evident seasonal variation. The high concentration of K+ and biomass burning potassium (K+BB) in PM2.5 in autumn and winter and its good correlation with black carbon (r = 0.74) suggest that the most severe pollution derives from biomass burning. Factor analysis results indicate that road dust, combustion processes (biomass burning and fossil fuels combustion), sea salt from marine sources and industrial activities are main sources of aerosol pollution in Lin'an.