Sulphur isotopic and chemical compositions of the natural waters in the Chuncheon area, Korea

The contribution of Chinese sources to the acid deposition in neighbouring countries in Far East Asia has been disputed. This study is to examine the isotopic composition of the S in the natural waters in the Chuncheon area to see if the isotopic composition can be an indicator of the pollution sources in the area. Meteoric water sampled between September 2000 and July 2001 and surface water sampled in December 2000 and April 2001 in the area were collected to examine their chemical and isotopic compositions. The pH values of the meteoric water lie between 4.02 and 6.89, but mostly lower than 5.6, indicating considerable acid deposition. The pH of the surface water is generally higher than that of the atmospheric water. Factor analysis on the concentrations of the dissolved components suggests that the surface water chemistry depends principally on the chemistry of the atmospheric water. The dissolution of carbonate minerals and silicate-water interaction plays a rather minor role in affecting the water chemistry. δ18O and δD of all the natural water samples align fairly well along the global meteoric water line. The δ34S of the dissolved SO4 in the meteoric water has values ranging from 3.4 to 8.2‰, showing little seasonal difference. The contribution from sea-salt to the total atmospheric S is estimated to be less than 10%. The δ34S of the anthropogenic S in the Chuncheon atmosphere is calculated to be 2.5 to 7.2‰, which partly overlaps the reported values of S in Chinese coal, Chinese rainfall, and Japanese fallout. Appropriate tracking and quantitative estimation of the contribution from possible pollution sources to the local S concentrations requires more information on the isotopic compositions of the potential pollution sources. The δ34S of the dissolved SO4 in the surface water has values ranging from 3.2 to 6.2‰, which is a little narrower than that of the meteoric water. The δ34S and the concentration range of the dissolved SO4 in the stream water, the results from factor analysis on the compositional variables, and observations from geological field work suggest that most SO4 comes from the meteoric input, and that the δ34S of the surface water may be utilized for the investigation of tracing and identifying the sources of the atmospheric pollutant S in the study area.