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Historical gold mine tailings
Invasive & vulnerable species
Chinese mystery snails
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Approaching a century-old legacy of arsenic and mercury contamination.
Note: We are continuing this research in 2019-2020. If you are interested in potential applications of our research, joining our research group or would like to contribute to our data analyses, please email Dr. Linda Campbell.
Waste materials ("tailings") from mining activities which took place in the 1800's can remain contaminated and toxic even over 100 years later. This is a national and international issue. The DEEHR group is developing biomonitoring and remediation approaches for impacts of those tailings on freshwater ecosystems and organisms which rely on those freshwater resources. Our focus is on Nova Scotia legacy gold mine tailings, and our goals are to develop methodology which can be used to remediate not only those sites but can also be applied to similar impacted sites around the world.
Nova Scotia has a long history of gold mining going back to the mid-1800’s. There are over 360 gold mines in 64 historic gold mining districts in the Cambro-Ordovician Meguma Supergroup, stretching over a 300-km length of NS. Between 1862 and the mid-1940’s, 1.2 million troy ounces of gold were extracted, typically using mercury amalgamation techniques. Due to a lack of environmental regulations in the 1800’s, there is a modern legacy of three million tonnes of finely-ground contaminated waste tailings.
Mercury and arsenic remain elevated and of concern even 100 years later. Mercury-recovery techniques were practiced, but frequently 10 – 25% of mercury was lost to the environment through various means at each ore processing site. It has been conservatively estimated that a total of 3.7 to 9.1 tonnes of mercury may have been released to the NS environment from the 1850’s to the 1940’s. Since the original ore also included arsenopyrite and other arsenic-bearing pyrites, the gold-mine tailings also contain elevated arsenic. After processing, untreated tailings were frequently slurried into nearby freshwater systems without regard for the consequences. The legacy of localized tailing wastes near freshwater sites in 64 gold-mine regions has resulted in multi-generational chronic exposure to mercury, arsenic and other toxic elements for wildlife and humans. Many sites across Nova Scotia still bear the visible scars of this extensive mining and processing a century later.
We are doing something about this major environmental issue. There has been many excellent studies of arsenic and mercury exposure and impact in terrestrial ecosystems and geology. However, there is a significant knowledge gap for aquatic ecosystems of Nova Scotia, with only a few publications and reports on this topic.
The DEEHR team is carrying out several investigations looking at this significant environmental and industrial issue for Nova Scotia, including:
- Legacy of gold mining impacts in Nova Scotia.
- Mercury and arsenic issues.
- NS Gold Mine Contaminants
- Useful resources.
All images and content copyright (c) Linda Campbell and other members of Dynamic Environment & Ecosystem Health Research Group. Map of gold-bearing deposits is from the Canadian Geographic Magazine (Sept/Oct 1994).