• Journal of Soil and Groundwater Environment
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• v.10 no.5
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• pp.25-36
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• 2005

Several metalliferous and coal mines, including Myungjin, Seojin and Okdong located at the upper watershed of Okdong stream, were abandoned or closed since 1988 due to the mining industry promotion policy. Thus these disposed an enormous amount of mining wastes without a proper treatment facilities, resulting in water pollution in the downstream areas. Acid mine drainage (AMD) and waste water effluents from the closed coal mines were very strongly acidic showing pH ranges of 2.7 to 4.5 and had a high level of Total Dissolved Solids (TDS) showing the ranges of 1,030 to 1,947 mg/L. Also heavy metal concentrations in these samples such as Fe, Cu, Cd and anion such as sulfate were very high. Concentrations of water soluble heavy metals in the Okdong streams were in the orders of Fe>Al>Mn>Zn>Cu>Pb>Cd, indicating Fe from the AMD and waste water effluents contributed greatly to the quality of water and soil in the lower watershed of Okdong stream. Copper concentrations in the effluents from the tile drainage of mine tailings dams were highest during the raining season. Water Pollution Index (WPI) of the surface water at the upper stream of Okdong river where AMD of the abandoned coal mines was flowed into main stream were in the ranges of 16.3 to 47.1. On the other hand, those at the mid stream where effluents from tailings dams and coal mines flowed into main stream were in the WPI ranges of 10.6 to 19.5. However, those at the lower stream were ranged from 10.6 to 14.9. These results indicated that mining wastes such as AMD and effluents from the closed mines were the major source to water pollution at the Okdong stream areas.

• Korean Journal of Environmental Agriculture
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• v.20 no.1
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• pp.20-27
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• 2001

Stream water chemistry in the abandoned Boeun Jeil coal mine area was studied for a period of 3 months, including rainy and dry season. The stream waters were a nearly neutral and slightly alkali condition, and $Mg-SO_4$ type with Mg>Ca>Na>K and $SO_4>HCO_3>Cl>NO_3$. Chemical composition of the stream water was quite irregular during the experimental period. Concentrations of Na, K, $HCO_3$, U, Sr, and Cr decreased by $10{\sim}30%$ during rainy season, caused by dilution effects with rain. The concentration of Ca, Mg, $NO_3$, Cd, and Co increased during the rainy season, caused by more easily dissolved from bedrocks or mine drainage with slightly acidic condition than dry season. The stream water was enriched in Mg, Ca, $HCO_3$, $SO_4$, Al, Fe, Zn, Ni, Co, Cr, Cd, Sr and U. Concentrations of Na, Mg, Ca, $SO_4$, $HCO_3$, Fe, Zn, Ni, Sr, and U decreased linearly with distance from the mine adit. These elements were strongly controlled by dilution of unpolluted water influx and/or adsorption on the clay minerals and iron oxyhydroxide precipitates. This mine area exhibited two main weathering processes ; 1) oxidation with acidification derived from Fe sulphides, and 2) pH buffering due to Ca and Mg carbonate dissolution. This weathering processes were followed by adsorption of metals on iron oxyhydroxides and precipitation.