Arsenic found in Long Lake
Study finds mining byproduct in nearby recreational water bodies; researchers trying to determine pre-mining levels
Evan Kiyoshi French
Northern News Services
Thursday, December 3, 2015
SOMBA K'E/YELLOWKNIFE
A study looking at arsenic concentration in lake sediment in and outside of the Giant Mine and Con Mine lease areas, has found harmful arsenic trioxide in two popular recreational lakes.
Martin Van Den Berghe, a master's student in environmental geochemistry from the University of Queens, Heather Jamieson, professor for the university's department of geological sciences and engineering, Mike Palmer, environmental scientist for the GNWT and Jennifer Galloway, research scientist for the Geological Survey of Canada, have more than 20 years of experience between them researching the environmental impacts of Giant Mine. - Evan Kiyoshi French/NNSL photo
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Jennifer Galloway, a research scientist who worked to produce the Geological Survey of Canada's Open File Report - released late last month - said she began looking at arsenic levels around Yellowknife in 2009. She said the most alarming finding in the recently released report is that arsenic trioxide is being found as far from the mine sites as Long Lake and Martin Lake, plus a handful of other, smaller lakes. Galloway said her team surveyed lakes stretching all the way up the Tibbitt to Contwoyto Road and from Yellowknife down to Hay River but another team working on the same project - from Queen's University - who were looking directly at arsenic levels in lake sediment - found the harmful mineral in the nearby lakes.
Whereas arsenic sulphide can be naturally occurring, arsenic trioxide almost never is.
"It occurs from roasting of ore," she said.
In order to release gold from ore, the gold mines of the day had to roast it at high temperatures, which released arsenic-rich gas.
"And naturally occurring arsenic has a different mineral form. Very rarely will it be arsenic trioxide."
The latter's high toxicity means it can cause serious harm, she said.
Heather Jamieson, a Queen's University professor overseeing a team of student researchers looking specifically at lake sediment arsenic levels said her team looked at five lakes at the edge of the mines areas and a bit further away. They found arsenic trioxide in Martin Lake, Long Lake, Lower Martin Lake, Handle Lake and BC 20. (A very small lake).
The arsenic trioxide in Martin and Long lakes, five kilometres from where ore roasting took place, was found in much lower quantities and mostly deep in the sediment at the west end of the lake.
"Sediments near the beach are very low in arsenic," said Jamieson, adding no arsenic trioxide was found at the beach. Only the more-stable and less dangerous arsenic sulfide was found in the popular swimming areas, she said.
Baseline studies sought
Galloway said researchers are trying to find out what the arsenic concentrations were in the lakes before mining began. In order to figure out what arsenic levels were prior to the advent of Northern mining - so targets can be set for remediation - Galloway said researchers will begin analyzing levels in isolated lakes around the North, financed by the Canadian High Arctic Research Station. Since there is no arsenic data stretching back to the 1930s, they'll look at Northern lakes isolated from mining to get an even better picture of what levels around Yellowknife might have once been. Their spatial survey and lake core samples have been used to establish a baseline for arsenic in lake sediment, she said, and what they're finding is remediation targets set so far are higher than that baseline.
"Throughout that Yellowknife area we determined pre-mining geochemical background is probably between 20 to 30 parts per million for arsenic," she said.
Natalie Plato, deputy director of the Giant Mine Remediation Project with Indigenous and Northern Affairs Canada, stated in an e-mail the remediation targets for sediments at Giant Mine haven't been set.
"While natural background or pre-mining conditions, if known, may be considered, reducing risk to the public and environment remains the top priority for the Giant Mine Remediation Project Team," she wrote.
Judy McLinton, spokesperson for the Department of Environment and Natural Resources - said arsenic concentration levels will be set by the Yellowknife Arsenic Soil Remediation Committee and they will be based on a human health risk assessment.
Jamieson said she's surprised arsenic trioxide is still present.
"I think one thing I was a little bit surprised about was to find arsenic trioxide persisting throughout the soils for decades. It's a very soluble compound. If you look it up in a chemistry book, you might think the rain and snow-melt should have washed it all away.
