Natural wetlands treating mine drainage

Birchtree Mine, Thompson, Manitoba, Canada

Water from the Birchtree nickel mine has been discharged for the past 30 years into an extensive 95 ha sedge-dominated fen (Photo 1). Its flow averages 320 L/min. during the ice-free season. The water is net alkaline (pH 8.4) and contains an average of 5.1 mg/L Ni. In addition, nickel is deposited as dust from a nearby smelter at an average rate of 0.17 kg/ha/m, from dust created by haulage trucks on the adjacent road (by an undetermined amount), and from rainfall.

Natural wetland at the Birchtree Mine, Thompson, Manitoba, Canada
Photo 1. Natural wetland at the Birchtree Mine, Thompson, Manitoba, Canada. This is a fen typical of the northern boreal forest. Photo by A. Hambley, INCO Ltd, Manitoba Division.

Accounting for all sources, the wetland retained a minimum of 96% of input nickel in 1994/95, mostly within an area measuring 1.8 ha. Nickel concentrations at its outlet averaged 0.08 mg/L. Concentrations in the discharge as low as 0.01 mg/L have been recorded. Nickel is entirely retained in sediments, in the forms indicated below.

ChartObject Speciation of Nickel in wetland sediments

I'd like to thank Al Hambley, Environmental Coordinator, Manitoba Division, INCO Ltd, for providing me with the above information

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