Vertical variations of heavy metals in tailings site of the Sangdong W mine, Korea

The objective of this study is to investigate the vertical variation of heavy metals in tailings from the Sangdong W mine. Tailings samples were taken at 6 drilling sites with 50cm intervals up to 21 meters in depth and dried at room temperature. The pH value, loss-on-ignition and water contents were measured. In addition, chemical compositions of the samples were determined by AAS after 0.1 N HCl leaching and ICP-AES after aqua regia leaching. The pH values were in the range of 7.4 to 9.5 due to chemical reactions of carbonate minerals. The ranges of heavy metals (mg/kg) extracted by 0.1N HCl were from 0.17 to 0.93 for Cd, 0.04 to 4.39 for Cu, 0.03 to 10.9 for Pb and 0.06 to 14.1 for Zn and those extracted by aqua regia were $3.10\~10.5,\;23.61\~251,\;63.7\~337\;and\;42.6\~134$ for Cd, Cu, Pb and Zn, respectively. Generally, the metal concentrations in tailings extracted by 0.1N HCl decreased with depth, whilst those extracted by aqua regia have a tendency to increase with depth in some case. Those trends might be due to the change of oxidation-reduction condition of the tailings.