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Technical Work on Arsenic in Mining

Jamie Kneen Communications and Outreach Coordinator responsible for: strategic research, social media, and public engagement; our Africa program, environmental assessment, and uranium mining.

A technical workshop on arsenic was organized by the Mining Association of Canada and CANMET, in association with the Arsenic Workshop Organization Committee. It was held in Winnipeg on November 7 & 8, 2002. There were about 74 participants from federal and provincial Government, industry, academia, consulting firms, aboriginal societies. Catherine Coumans was one of two CEN representatives. Minutes from the meeting are still forthcoming from CANMET.

Arsenic is a common component in tailings impoundments. The presentations made it clear that there is still a lot that is not yet well understood about arsenic in mining, for example:

  • how arsenic is retained and released, i.e. binding processes, and how this affects long term stability.
  • microbial transformation of arsenic, chemical mobility and chemical speciation.
  • need to develop data on bioavailable forms of arsenic and environmental health and risk factors associated with arsenic, specifically; stability, speciation and bioavailability.
  • the long term stability of arsenic in submerged tailings and other reducing conditions
  • treatment methods for arsenic trioxide
  • need to study aerobic and anaerobic conditions for long term arsenic generation
  • more research is needed in ecological and human risk assessment of arsenic
  • need to know more about the fate and behaviour of arsenic during mill processing and waste treatment

An important finding of recent research is that arsenic in reducing environments (underwater in natural or artificial impoundments, such as lakes or tailings ponds) will be more readily mobilized to the water column through the activity of arsenic scavenging mechanisms. Reducing conditions are created where there is a food source for micro-organisms. In mining areas, high concentrations of nutrients such as natrium and potassium resulting from the mining process encourage biological production, creating reducing conditions and increasing the likelihood of arsenic mobilization to the water column. In the case of Balmer Lake, a naturally oligotrophic lake became eutrophic through nutrient loadings as a result of mining, and the lake become more susceptible to arsenic mobilization.

The workshop concluded with agreement that some form of arsenic working group should be established.