ENVIRONMENTAL IMPACTS OF THE ERDENET COPPER MOLYBDENUM MINE IN NORTH CENTRAL MONGOLIA

Surface and ground water and alluvial deposits were sampled in 2008 at six locations in north central Mongolia along the Khangal River, and three locations within the tailings storage complex. Metals concentrations were determined using atomic absorption (AA) flame and graphite furnace and x-ray florescence. Chromium (Cr) from 0.1 to 7.1 mg/kg, arsenic (As) from 1.8 to 5.1 mg/kg, lead (Pb) from 0.1 to 0.9 mg/kg, and copper (Cu) from 2.7 to 58.7 mg/kg were detected in stream and terrace deposit sediment samples. Chromium (Cr) from 6.9 to 13.1 mg/kg, arsenic (As) from 9.3 to 10.7 mg/kg, lead (Pb) from 0.2 to 2.3 mg/kg, and copper (Cu) from 61.4 to 96.1 mg/kg were detected in tailings storage facility samples. Arsenic was identified as a parameter of concern in water samples with values ranging from 6.0 to 13.8 ug/L in ground water and 3.7 to 24.6 ug/L in surface water. Based on measured stream flow rates, arsenic loading rates ranged from 40 to 470 g/day. Naturally high levels of arsenic occur in the study area ground water, however, arsenic levels in the stream are elevated by mining activities. Wind direction and distance from the mine tailings on copper concentration in sediments were analyzed by linear, exponential, and curvilinear model fitting. The linear distance model best fit the data with a Pearson’s correlation coefficient (R²) of 0.77. The linear distance model predicted metal concentrations return to baseline levels at a distance of 6.4 km from the mine tailings dam. Our future work is to independently test our linear distance model using street dust and tree bark samples taken at the time of the stream sediment sampling.