Potential groundwater contamination with toxic metals in and around an abandoned Zn mine, Korea

This study evaluated potential groundwater contamination with toxic metals in and around an abandoned zinc mine in Korea. Water levels in the mine waste dump indicated occurrence of a losing stream during the period of peak stream flow as a result of snowmelt runoff, which posed the threat of groundwater pollution. The pH values for the groundwaters were near neutral to slightly basic, with a slight increase of the values along the stream flow direction. Higher values of electrical conductivity were observed in the mine area. High dissolved oxygen concentrations clearly indicated an oxygenated groundwater environment. High concentration of sulfate and most dominant Ca-SO4 type groundwaters represent effects of mine drainage and sulfide minerals. In the mine area, groundwater contamination by Zn, Al, Fe, and Mn was observed. Most of the toxic metals decreased with distance from the mine, some have decreased gradually or others more suddenly although some metals were also found in high concentrations- in downgradient area. Levels of toxic metals were relatively low in groundwaters downgradient of the mine, which may be due to the high pH and highly oxygenated conditions, and mixing with metal-free waters.