Wednesday, 6 April 2016

Lakes near Yellowknife contaminated with arsenic, mercury years after mine closing

Lakes near Yellowknife contaminated with arsenic, mercury years after mine closing  by IVAN SEMENIUK - SCIENCE REPORTER - The Globe and Mail - Published Wednesday, Apr. 06, 2016 "… The Ottawa study includes data from 25 lakes within a 25-kilometre radius of Yellowknife. In some cases, it found arsenic concentrations in the water as high as 136 micrograms per litre – more than 13 times the recommended limit for drinking water and 27 times the level deemed adequate for the protection of aquatic life. The highest concentrations were found in lakes within four kilometres of the Giant Mine site. […]
André Corriveau, the territory's chief public health officer, said he first learned of the findings last fall and has been gathering information for a public-health advisory, which he hopes to issue before the lakes thaw.
Dr. Corriveau added that his concern about the potential health risk is "low but not zero," since it is unlikely that anyone would be drinking from the lakes on a regular basis. The lakes are not widely used for recreation, he said, and have only recently become more accessible because of a new road. But he said anyone who may be camping or fishing should be made aware of the contamination. […]
Another surprising find relates to the elevated mercury levels in the lakes. The chief concern is not the total amount of mercury found, but the unusually high proportion that occurs as methyl mercury, a compound that is more deadly to humans than mercury alone. In lakes nearest the mines roaster, up to 44 per cent of the total mercury is in this form. The Ottawa researchers posit that bacteria living off sulphur emissions from the mine are responsible for converting mercury into methyl mercury.
While environmental contamination from the Giant Mine, along with a smaller mine that closed in 1971, is not a new theme, most of the attention until now has been directed toward the mine sites rather than the surrounding region. […]
Data from ongoing monitoring of 98 lakes by the territory has now been posted as an open file by the Northwest Territories Geological Survey.
"There's really been a ramping-up of research efforts," Dr. Palmer said, adding that a clearer picture of the extent and activity of the contaminants would be essential for determining what kind of risk they may pose.
Adam Houben, a PhD student who is lead author on the study and who did much of the sampling and analysis of the lakes, said the findings offer an example of the unforeseen consequences that can arise from resource development, much of which takes place outside of the public's awareness.
"There are real impacts on communities and on the greater landscape as well," Mr. Houben said. …'
Factors Affecting Elevated Arsenic and Methyl Mercury Concentrations in Small Shield Lakes Surrounding Gold Mines near the Yellowknife, NT, (Canada) Region by Adam James Houben, Rebecca D'Onofrio, Steven V Kokelj, Jules M Blais Published: April 6, 2016
NWT Open File 2015-06 The concentration of arsenic in lake waters of the Yellowknife area

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