Chemical characteristics of spring rainwater of Xi'an city, NW China

A comprehensive study on the chemical composition of spring rainwater was carried out in Xi'an, northwestern China. All samples were analyzed for pH, electrical conductivity and main ions (SO(4)(2-), NO(3)(-),Cl(-), F(-) Ca(2+), Mg(2+), K(+) Na(+) and NH(4)(+)). The pH varied from 5.14 to 7.45, with a volume-weighted mean pH of 6.64. The volume-weighted mean equivalent concentration of rainwater components followed the order SO(4)(2-) > Ca(2+) > NH(4)(+) > NO(3)(-) > Cl(-) > Mg(2+) Na(+) > F(-) > K(+) The dominant ions, SO(4)(2-), Ca(2+), NH(4)+ and NO(3)(-), accounted for 88% of the total ions. Significant positive correlation of SO(4)(2-), NO(3)(-) with Ca(2+) and NH(4)(+) and the calculated neutralization factors show that Ca(2+) and NH(4)(+) are the main neutralizing constituents. Sources of major ions were assessed based on the enrichment factor. Ca(2+), K(+) and Mg(2+) mainly originated from crust, whereas SO(4)(2-) and NO(3)(-) are mostly attributable to anthropogenic sources. The major likely source of NH(4)(+) was agricultural activities. (C) 2011 Elsevier Ltd. All rights reserved.