Hydrochemical Monitoring and Heavy Metal Contaminations at the Narim Mine Creek in the Sulcheon District, Republic of Korea

Abstract

The Narim gold mine is located approximately 200 km southeast of Seoul within the Sulcheon mineralised district in the Yeongnam massif, Korea. In this study, environmental geochemical analyses were undertaken for soil, sediment and water samples collected in April, September and November in 1998 from the Narim mine creek. The mine area consists mainly of granitic gneiss; however, mineral constituents of soil and sediment near the mine were mainly composed of quartz, feldspar, mica, amphibole, some pyrite and clay minerals. Also were found some pyrite, arsenopyrite, chalcopyrite, sphalerite, galena, malachite, goethite, various hydroxide and unidentified secondary minerals. Generally, high concentrations of heavy metals in the soil and sediment are correlated with a high proportion of secondary minerals. Hydrochemical compositions of water samples are characterised by relative significant enrichment of Na+ + K+ and alkali metals in the ground water, whereas the surface and mine waters are relatively enriched in Ca2+ + Mg2+ and heavy metals. Anion contents of the ground waters are typically enriched in HCO3−, NO3− and Cl−, whereas the surface and mine waters are highly enriched in HCO3− and SO42−. The pH and EC values of the surface water from the non-mine creek are relatively lower compared with those of the surface water around the mine and waste dump. The range of δD and δ18O values (d parameters) of the water samples are shown in distinct two groups for the April waters of 10.1–13.1, and for the November waters of 5.8–7.9, respectively. This range variation indicates that two group water were composed of distinct waters because of seasonal difference. Geochemical modelling showed that mostly heavy toxic metals may exist largely in the form of free metal (M2+) and metal-sulphate (MSO42−), and SO42− concentration influenced the speciation of heavy metals in the mine water. These metals in the ground water could be formed of CO3− and OH− complex ions. Using a computer program, saturation indices of albite, calcite, dolomite in mostly surface water show undersaturated and progressively evolved toward the saturation state, however, ground and mine waters are nearly saturated. The gibbsite, kaolinite and smectite are supersaturated in the surface and ground water, respectively. Calculated water-mineral reaction and stabilities suggest that the weathering of silicate minerals may be stable kaolinite. The clay minerals of K-illite and Na-smectite will be transformed to more stable kaolinite owing to the continuous reaction.