Chemical characteristics of rainwater in northeast China, a case study of Dalian

The samples of rainwater were collected at two urban sites and one rural site in Dalian from January to December 2007, and precipitation pH, conductivity, and main chemical components were analyzed. The dominant ions in rainwater were SO42−, NO3−, NH4+, Cl−, Ca2+ and Na+, which accounted for 92.03% of the total ions. Winter and spring had high concentrations of chemical components, while autumn and summer had relative low values. The dominant neutralization substances were NH4+, Ca2+, and Mg2+, and presented relatively lower neutralization capability than the other major acid rain city in north China. This caused precipitation was typically acidic with pH 4.79. Downtown has obvious lower precipitation pH, higher electrical conductivity value, higher concentrations of chemical components, and higher neutralizing capability than rural area. Furthermore, the possible common sources of major ions were identified based on backward trajectory analysis, correlation analysis, and source contribution. It presented that the chemical ion concentrations were influenced not only by local emissions but also transferred materials by wind from remote areas. SO42−, NO3−, and NH4+ were mainly from human activities, Ca2+, Mg2+, and K+ were soil derived, Na+ and Cl− were marine source, and the contribution of anthropogenic activities was also considerable for Cl−.

► Wet chemical constitute is discussed in northeast China. ► Rainwater in Dalian is typically acidic due to poor neutralization. ► Winter and spring have higher ion concentration than autumn and summer. ► Urban has higher ion concentrations and lower neutral potential than rural sites. ► Possible source for ions is identified by correlation analysis, backward trajectory, and rich factors.