Arsenic Legacy in Lake-Bottom Sediments from Historic Nova Scotia Mine Worries Researcher

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Findings from a research describing the arsenic legacy abandoned in lake-bottom sediments near a deserted Halifax gold mine are causing concern for a senior cancer researcher.

A paper published Monday in the journal Science of the Total Environment says a dated core sample taken from the bottom of Lake Charles discovered arsenic at 4,960 milligrams per kilogram, more than 280x higher than levels “where biological harm is expected.”

The location is downstream from the historic Montague mines, where successive gold rushes saw the creation of 121K tonnes of arsenic-rich tailings between the 1860s and 1940.

Notwithstanding the high carcinogen levels, the arsenic in sediments at the lake’s deepest point is rising closer to the water itself.

Joshua Kurek, an environmental scientist at Mount Allison University in Sackville, N.B., and one of the study’s co-authors, said in a recent interview the closeness of the arsenic to the lake water after a lot of time was not expected.

“We tend to think of sediments at the bottom of a lake as a sink for a lot of materials … but here’s a case where the pollutants from mining that ended 80 years ago are slowly moving up the core and are getting closer to the sediment-water boundary,” he said.

“If environmental conditions at the bottom of Lake Charles change, what can happen is some of those contaminants that were locked into the sediments can be released into the water column.”

The famous swimming and boating lake on the edges of Halifax already has high levels of arsenic at 11 micrograms per liter, twice the Canadian water quality guidelines for the protection of aquatic life and higher than 50 other lakes in the country, as per the federal Fisheries Department data.

In a province full of deserted mine sites, the journal article raised concerns for Dr. Graham Dellaire, the director of research in Dalhousie University medical school’s department of pathology.

The Halifax-based researcher is chairing a national team of experts looking at carcinogens that affect people’s risk of getting cancer.

Funding sought for an awareness campaign

He said in an interview this past week that whereas the public has often heard the message on the carcinogenic risk of being exposed to radon, many are still unaware of the risks of long-term exposure to arsenic and its links to various cancers.

Dellaire is trying to start awareness campaigns on arsenic, and he’s seeking funding to provide information to areas where there is great risk for contamination like areas downstream from abandoned gold locations.

He said the program would test well and invite persons to screen for personal arsenic exposure through sampling of their toenails.

“The ghost of our mining past is coming back,” he said.

Kurek said the upward migration of the arsenic in Lake Charles may be linked to urban influences on the lake.

The expert in freshwater ecosystems suggests with nutrients like fertilizer flowing in from surrounding properties, there are biological processes that can exhaust oxygen in the deeper reaches, and this chemical change in the water seems to be related to the increase of arsenic.

Funding previously announced for site cleanup

Warming water and other climate change effects could additionally be playing a role, possibly speeding the chemical processes that exhaust oxygen in the lake, he said.

The Lake Charles research comes around a year after another study suggesting more work is required to know the impact of arsenic and mercury on plants, mollusks, fungi, invertebrates, mammals and fish in Nova Scotia’s historic gold mining areas.

A 2020 paper published in the journal Environmental Reviews found just 18 of the 64 gold districts in N.S. have been analyzed for mercury and arsenic accumulation in different forms of life.

In July 2019, the provincial government said it was spending $48m to clean up the Montague location and the Goldenville site in Guysborough County. Overall, it said it was looking at a list of 69 deserted mining locations, including 24 gold mines, on Crown land so as to determine which ones needed containment or other work.

This arrived the same year the region’s auditor general issued a report concluding the territory has not sufficiently investigated potential contamination at many abandoned mine sites, meaning there could be untold future tolls on the government’s finances.

In a legislative committee hearing in April, Donnie Burke, executive director of N.S Lands, said remediation work at the Montague location is expected to begin by the next fiscal year.

‘A call to action’

Allison Clark, the lead author on the most recent paper, finished the work whilst completing her thesis at Mount Allison’s department of biology.

“I believe our study is a call to action to work on remediation efforts of the tailing sites,” she said.

Linda Campbell, a professor of environmental science at Saint Mary’s University and another co-author, stated in an interview that arsenic is an element that will stay in an ecosystem for a very long time.

She said the first move to remediation of the contaminated sites is to “stop the mobility of the [gold] tailing materials themselves,” at Montague and other locations.

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