Smith LJ, Ptacek CJ, Blowes DW, Groza LG, Moncur MC. Perchlorate in lake water from an operating diamond mine. Environmental Science and Technology. 2015 Jun 3.
Mining-related perchlorate [ClO4-] in the receiving environment was investigated at the operating open pit and underground Diavik diamond mine, Northwest Territories, Canada. Samples were collected over four years and ClO4- was measured in various mine waters, the 560 km2 ultra-oligotrophic receiving lake, background lake water and snow distal from the mine. Groundwaters from the underground mine had variable ClO4- concentrations, up to 157 µg L-1, and were typically an order of magnitude higher than concentrations in combined mine waters prior to treatment and discharge to the lake. Snow core samples had a mean ClO4- concentration of 0.021 µg L-1 (n=16). Snow and lake water Cl-/ClO4- ratios suggest evapoconcentration was not an important process affecting lake ClO4- concentrations. The multi-year mean ClO4- concentrations in the lake were 0.30 µg L-1 (n=114) in open water and 0.24 µg L-1 (n=107) under ice, much below the Canadian drinking water guideline of 6 µg L-1. Receiving lake concentrations of ClO4- generally decreased year-over-year and ClO4- was not likely [biogeo]chemically attenuated within the receiving lake. The discharge of treated mine water was shown to contribute mining-related ClO4- to the lake and the low concentrations after 12 years of mining were attributed to the large volume of the receiving lake.