Assessments of natural and anthropogenic controls on the spatial distribution of stream water quality in Southeastern Korea

Hydrogeochemical and geostatistical analyses were conducted to evaluate natural and anthropogenic effects using stream water data of Southeastern Korea acquired through the Hydrogeochemical Survey Program of the Korea Institute of Geoscience & Mineral Resources. The results of a variographic analysis of the spatial structure of stream water quality show that the semivarigrams of Ca, Mg, and HCO₃ have similar patterns and regional distributions, reflecting the same geogenic source of Paleozoic, Tertiary, and Cretaceous sedimentary rocks. Although Ca and Mg originated from Paleozoic sedimentary rocks, the distribution of Mg is significantly different from that of Ca due to the presence of dolomite in northeastern area of Korea, which enhances the Mg concentration in stream water. Studies of mineralization and acid mine drainage resulting from previous mining activities reveal a high Ba in sedimentary rock from of Kyongsang basin, as well as anomalous concentration of Al, Fe, and SO₄ in the Ogcheon and Tabaeksan mineralization areas. Saturation indices of barite determined using average Ba and SO₄ concentrations in stream water suggest the existence of barite mineralization deposits in sedimentary rock of Kyongsang Group. Na, Cl, K, NO₃, and Cl, exhibit effects of anthropogenic and marine sources in the stream water, with increasing values near residential, agricultural, and coastal areas. Cokriging analyses employing Ca-HCO₃, Ca-Sr, Ba-SO₄, and Na-Cl also revealed the nature of bedrock geology, mineralization, and anthropogenic and marine sources.