Geochemical characteristics of the acid mine drainage in the water system in the vicinity of the Dogye coal mine in Korea

This study investigated geochemical characteristics of the acid mine drainage (AMD) discharged from the abandoned mine adits in the vicinity of the Dogye coal mine in Korea. Acid mine drainage discharged from Jeoncha pit adit of the Dogye coal mine, which is the main source of the AMD in the study area, had a pH value of 3.0 and concentrations of 2148 mg SO42- L-1, 229 mg Fe L-1, 71 mg Al L-1 and 11 mg Mn L-1. The reduction of some metal concentrations downstream from the discharge point could be explained on the basis of dilution and precipitation. The order of removal of metal ions downstream from the discharge point was Fe > Al, Cu > Zn, Mn. Acidity could be used as a good determining factor offering comprehensive and quantitative values for the polluting extent of acid mine drainage. The acidities existing in all acidic water samples in the Gunahan district originated primarily from mineral acidity, especially in the upper Nahan Creek from dissolved Fe and Al and in the middle and down Nahan Creek from dissolved Al. From the application of the WATEQ4F program, it was determined that predominant species of dissolved Fe in all water samples was Fe2+, and those of dissolved Al were AlSO4+ and Al3+ except for IW2 sample which was associated with white precipitates. The species of dissolved Al in IW2 sample include also AlOH2+ and Al(OH)(2)(+). The saturation indices of goethite and haematite were positive in the water samples associated with ochrous precipitates (usually called 'Yellow Boy'), therefore these solids might be precipitated. For the IW2 sample, the saturation indices of amorphous Al(OH)(3) and gibbsite were positive, so theoretically these solids might also be precipitated. By XRD analysis, it was found that goethite occurs in ochrous precipitates, and gibbsite in white precipitates.