Chemical compositions of wet precipitation and anthropogenic influences at a developing urban site in southeastern China

Abstract

A comprehensive study on the chemical compositions of wet precipitation was carried out from January 2004 to December 2004 in Jinhua, southeastern China's Zhejiang Province. All samples were analyzed for pH, electrical conductivity and major ions (F −, Cl −, NO 3 −, SO 4 2−, K +, Na +, Ca 2+, Mg 2+ and NH 4 +). The rainwater was typically acidic with a volume-weighted mean pH of 4.54, which ranged from 3.64 to 6.76. SO 4 2− and NO 3 − were the main anions, while NH 4 + and Ca 2+ were the main cations. The concentrations of these major ions were generally higher compared to those reported in other parts of the world, but much lower than those in northern China. Wet deposition fluxes of major ions showed pronounced seasonal variations with maximum in spring and minimum in autumn. Significant correlations were found in soil-derived species among Ca 2+, Mg 2+ and K + and sea-salt species between Na + and Cl −. Other relatively good correlations were also observed between Ca 2+ and SO 4 2-, Mg 2+ and SO 4 2-, Mg 2+ and NO 3 −, Mg 2+ and Cl −. Principal component analysis was also performed on individual precipitation to find possible sources of the major ionic species. Varimax rotated four components accounting for 85.9% of the total variance, and were interpreted as acid and alkaline pollutants, sea spray and mixed source, soil and acid/neutralization. Calculation of enrichment factors for rainwater components relative to soil and seawater indicated that Ca 2+ and K + mainly originated from the terrestrial source, and SO 4 2- and NO 3 − were mostly attributed for the anthropogenic activities in the study area. In general, the results suggested that precipitation chemistry is strongly influenced by anthropogenic sources rather than natural and marine sources. The pollutants in rainwater were mainly derived from long distance transport, local industry and traffic sources.