Abstract

The objectives of this study are (1) to determine the extent and degree of As contamination of the water and sediments influenced by mining activity of the abandoned Au-Ag mines, (2) to examine As speciation in contaminated water, (3) to monitor variation of As contamination in water system throughout the dry and wet seasons, and (4) to investigate the As chemical form in the sediments through the sequential extraction analyses. Natural water(mine water, surface water and groundwater) and sediments were collected in six abandoned Au-Ag mine(Au-bearing quartz veins) areas. The contamination level of As in mine water of the Dongil(524 μg/L) is more higher than the tolerance level(500 μg/L) for waste water of mine area in Korea. Elevated levels of As in stream water were also found in the Dongil(range of 63.7~117.6 μg/L) and Gubong(range of 56.1~62.9 μg/L) mine areas. Arsenic contamination levels in
groundwater used by drinking water were more significant in the Dongil(11.3~63.5 μg/L), Okdong(0.2~68.9 μg/L) and Gubong(2.0~101.0 μg/L) mine areas. Arsenate[As(V), H2AsO₄^?] is more dominant than arsenite[As(III), H₃AsO₃] in water system of the most mine areas. The concentration ratios of As(III) to As(total), however, extend to the 95% in stream water of the Okdong mine area and 70~82% in groundwater of the Okdong and Dongjung mine areas. As a study of seasonal variation in the water system, relatively high levels of As from the dongil mine area were found in April rather than in September. Sequential extraction analysis showed that As was predominantly present as coprecipitated with Fe hydroxides from sediment samples of the Dongjung and Gubong mine(35.9~40.5%), which indicates its possibility of re-extraction and inducing elevated contamination of As in the reductive condition. In sediments from the
Dongil, Okdong and Hwachon mine area, high percentage(55.2~83.4%) of As sulfide form was found.

Keywords abandoned A u-Ag m ine arsenic, arsenic speciation, sequential extraction