Spatial and seasonal variability of water-soluble ions in PM _2.5 aerosols in 14 major cities in China

We analyzed PM _2.5 aerosols from 14 major cities in China for concentrations of water-soluble (WS) major and trace elements (Na, Mg, Ca, K, Fe, Mn, Zn, Rb, Sr, Ba, Pb, S and Cl). The main focus was to examine patterns in spatial distribution and seasonal variability. Using principal component analysis, we identified three general sources for WS-elements in aerosols as anthropogenic, seasalts and fine dust particles originating from soils. The spatial patterns identified show that anthropogenic activity is the most important factor influencing the concentration of heavy metals in aerosols. Concentrations of WS-S, Zn and Pb were correlated with the locations of major industrial zones, and regulated by topography and seasonal weather patterns. We found higher WS-metals concentrations during the winter season, probably related to coal combustion in northern China. Moderate correlations of WS-S, Zn, Pb and Cl suggest that coal combustion releases. The seasonal pattern in WS-Fe concentrations shows the importance of acid precipitation events where coal combustion contributes to additional Fe (II) deposition. The findings of this study support the argument that WS-S in fine particles enhanced the production of hydrogen ions act to reduce the pH values of precipitation. Our interpretation of these spatial and seasonal patterns in WS-major and trace elements in aerosols highlights the need for continued research on trends in acidic deposition in major industrial cities in China.