Chemical characteristics of spring rainwater of Xi’an city, NW China: Fid-Bau Portal

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

Lu, Xinwei / Li, Loretta Y. / Li, Nan / Yang, Guang / Luo, Dacheng / Chen, Jinghui

Abstract 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 (SO4 ²⁻, NO3 ⁻, Cl⁻, F⁻, Ca²⁺, Mg²⁺, K⁺, Na⁺ and NH4 ⁺). 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 SO4 ²⁻ >Ca²⁺ >NH4 ⁺ >NO3 ⁻ >Cl⁻ >Mg²⁺ >Na⁺ >F⁻ >K⁺. The dominant ions, SO4 ²⁻, Ca²⁺, NH4 ⁺ and NO3 ⁻, accounted for 88% of the total ions. Significant positive correlation of SO4 ²⁻, NO3 ⁻ with Ca²⁺ and NH4 ⁺ and the calculated neutralization factors show that Ca²⁺ and NH4 ⁺ are the main neutralizing constituents. Sources of major ions were assessed based on the enrichment factor. Ca²⁺, K⁺ and Mg²⁺ mainly originated from crust, whereas SO4 ²⁻ and NO3 ⁻ are mostly attributable to anthropogenic sources. The major likely source of NH4 ⁺ was agricultural activities.

Highlights ► SO4 ²⁻, Ca²⁺, NH4 ⁺ and NO3 ⁻ are the predominant ions in the rainwater of Xi’an. ► The pH value of rainwater in Xi’an is 6.64 which neutralized by Ca²⁺ and NH4 ⁺. ► About 21% of acidy of Xi’an rainwater was due to NO3 ⁻ and 79% due to SO4 ²⁻. ► Total ions concentration shows atmospheric environment of Xi’an is severe polluted. ► The major ions of Xi’an rainwater originated from anthropogenic and soil sources.