SOMBA K'E/YELLOWKNIFE
Nearly half the lakes within a 30-kilometre radius of Giant Mine have drinking water levels that exceed Canadian drinking water standards, according to a recent study which was presented at the Yellowknife Geoscience Forum late last month.

Forty-four per cent of lakes within a 30-kilometre radius of Giant Mine have arsenic levels above the recommended drinking guideline of 10 parts per billion. - NNSL file photo Arsenic is being 'recycled' by plants In some instances, plant life may be "recycling the arsenic," around Giant Mine from the more dangerous arsenic trioxide into arsenic sulphide, which is more naturally occurring and doesn't dissolve as easily in water, a study found. "It would be a lot more stable that way," said Martin Van den Berghe, a summer master's student from Queen's University, who conducted a study of the sediments in three lakes downwind from Giant Mine to better understand the chemical makeup of the arsenic contained within them. Although arsenic is more stable in the sulphide state, Van den Berghe found the chemical process can go back and forth so that arsenic becomes transformed back into arsenic trioxide after the initial transformation. Alternatives North's Kevin O'Reilly said Van den Berghe's findings are encouraging but more studies will be required to gauge their implications. "It does start to raise more questions about the need to do more monitoring and research around this and better understand if there is indeed any way to remediate this material," he said. Professor Heather Jamieson, an arsenic expert at Queen's University's Department of Geological Sciences and Geological Engineering, has been studying arsenic levels in Yellowknife for more than 15 years and is supervising Van den Berghe's thesis. She said the fact that the arsenic trioxide is not dissipating is at odds with its chemical characteristics. "If you look in a chemistry textbook and look up the pure solubility of pure arsenic trioxide, it's highly soluble," she told Yellowknifer at the Yellowknife Geoscience Forum, Nov. 27. "I was a little bit surprised ... that we found it still persisting." Jamieson suggested one of the reasons the arsenic may not be dissolving at its expected rate is because of the extremely cold temperatures and long winters. She added, however, other factors could contribute to the phenomenon and said more research on the topic is required.

The study, conducted by the Department of Environment and Natural Resources in conjunction with Carleton University and the Geological Survey of Canada, tested arsenic levels in 100 lakes within a 30-kilometre radius of the mine between 2012 and 2014.

The research found that 44 per cent of the lakes tested had arsenic levels that were higher than the recommended drinking guideline of 10 parts per billion. According to Mike Palmer, an environmental monitoring specialist with the territorial government, recorded levels of dissolved arsenic ranging from as low as 0.5 parts per billion up to 1,050 parts per billion, the latter being a small lake one kilometre from the roaster at Giant Mine.

One of the factors mapped out in the research was the location of lakes in relation to the roaster's smokestack based on the prevailing wind direction, which historically comes from the southeast.

Palmer said lakes that were downwind (to the northwest) of the mine had the highest concentrations of arsenic, with the implication being that the arsenic came from emissions carried from Giant Mine's roaster. In order to release gold from ore, the latter has to be roasted at high temperatures – a process that released arsenic-rich gas.

"As you move away from the roaster complex arsenic levels get lower," Palmer said during a presentation at the geoscience forum Nov. 27.

Other factors that affected arsenic concentrations were the lakes' geology, whether they were closed or connected to other water sources and their size, with smaller lakes often registering higher levels than larger ones because they provide less room for the arsenic to dissipate.

"The ones that were really high, especially the ones that were between 500 and 1,000 parts per billion are these small organic-rich lakes that people don't tend to use. The lakes that people tend to use – the larger recreational lakes – tend to have lower arsenic because ... they're bigger so there's more dilution and there's a greater movement of water through them," Palmer told Yellowknifer after the presentation.

Risk level unknown

Although the higher concentration of arsenic downwind from the mine suggests the arsenic came from there and is therefore arsenic trioxide, differentiating between the various "species" of arsenic is outside the scope of Palmer's research.

Naturally occurring arsenic can be found readily in soil and rock samples around Yellowknife and is not nearly as harmful to humans as arsenic trioxide because it as not as soluble in water. It is therefore not as easily absorbed by the digestive system.

While baseline numbers are not available for water samples around Yellowknife, a 2001 study by the Environmental Sciences Group found the typical concentration range of arsenic in soil in the Yellowknife area away from the mine is between three and 150 parts per million – up to 12.5 times higher than the Canadian Soil Quality Guidelines of 12 parts per million. Another study, conducted in 2012, found that between 30 to 40 per cent of the arsenic gathered from a series of three soil samples on the Giant Mine property were soluble in human gastric fluid.

Risks are 'negligible'

Dr. Kami Kandola, deputy chief public health officer for the GNWT, said the federal government's arsenic thresholds for drinking water are based on the potential harm that would be incurred by consuming one litre of contaminated water per day over a 20 to 25 year period.

As a result Kandola said the risks associated with drinking water from lakes that had up to five times the drinking water guidelines would be "negligible."

Kandola added that as a carcinogen, the major concern with chronic exposure to high levels of arsenic is cancer.

"If someone was drinking (water with arsenic contamination of) 1,000 parts per billion they might start incurring some negative effects over a shorter term," she said.

Giant Mine was in full operation for about 50 years, with ore no longer being processed after 1999.

We welcome your opinions. Click here to e-mail a letter to the editor.