Water quality impact of mining in the Wolmyoung area of Korea, and its short-term changes

The water quality of a stream affected by mining activities was investigate d on the basis of a mineralogical study for the related solids, and their s ubsequent changes were monitored for a year, so as to clarify the impact of the acid mine drainage (AMD) to the stream. The mine-affected stream was c lassified into Ca-Mg and sulfate type, and the concentrations of its major constituents ranged from tens to hundreds times higher than those of the ba ckground stream. This was most likely due to acid-generating reactions invo lving the oxidation of sulfides in the mineralized zone, and subsequent neu tralizations involving calcite and chlorite as possible sources of Ca and M g, respectively. This interpretation is consistent with the thermodynamic a nd mass-balance calculations. The concentrations of the dissolved constitue nts changed seasonally, depending largely on rainfall in the mine-affected stream. However, the dramatic decrease in the ratio of Mg/Ca, independent o f rainfall, indicates that some changes did occur in sources, including the heterogeneous distribution of main source materials, the change in chemica l conditions, especially in pH, pe(Eh), and P-CO2, in the reacting fluid, a nd the consequential solubility changes in sources. In spite of the limitat ions of short-term monitoring, it does provide some meaningful information in order to construct a long-term monitoring program.