A mass balance approach to estimate the dilution and removal of the pollutants in stream water polluted by acid mine drainage

A few simple mass balance equations were developed to simultaneously estima te how much the pollutants from acid mine drainage (AMD) in stream water ar e diluted and removed during their migration. The application of the equati ons requires knowledge of the variations in the concentrations of the disso lved pollutants and the stoichiometry of the precipitation reaction of the pollutants when none of the pollutant shows a conservative behavior along t he stream path. The calculation should be restricted to the pollutants show ing much higher concentrations in the polluted main stream water than in th e combining or diluting water of the same target area. The mass balance equ ations were applied to estimate the dilution factor and precipitation fract ions of pollutants in Imgok Creek such as Fe, SO4 and Al, from the AMD of Y eongdong mine. The results show that the estimation, especially for SO4 and Al, significantly depends on the kinds of the precipitate, the maximum rem oval fractions of SO4 and Al by precipitation are respectively 34% and 46% of the original input, which is much higher than the values estimated when SO4 is considered to be perfectly conservative. It indicates that the stoic hiometry of precipitation reaction is very important in the interpretation of the pollutant dilution and migration and assessment of environmental imp acts of AMD. The applicability of the mass balance equations may still need to be verified. However, examining the calculated dilution factor and prec ipitation fractions with the equations can provide invaluable information o n not only the behavior but also unexpected input of the pollutants in the stream water polluted by AMD and other point sources.