Geochemistry of Submerged Tailings in Anderson Lake, Manitoba: Recent Results

Abstract

Sulfide-rich zinc-, copper-, and lead-bearing tailings have been deposited via floating pipeline into shallow(< 8 m) Anderson Lake in north-central Manitoba since 1979. The lake water contains elevated levels of dissolved metals which are derived mainly from an acid-generating roadway along the north shore. Water-column sampling and sediment coring were carried out through the ice on Anderson Lake in April 1993. Two sites were occupied, one proximal to the tailings discharge (Station B, the "pure tailings" site) and the other about 2 km away (Station A, the "natural sediments" site). Interstitial waters were extracted from duplicate cores collected at each location. The water column was strongly stratified at both locations, exhibiting four layers at the natural sediments site (two of which were dysaerobic or anoxic), and two layers near the tailings outfall, the lower being dysaerobic. The unusual multiple layering probably reflects the influence of laterally variable advective processes. High concentrations of dissolved iron in shallow pore waters indicate that the sediments at both locations were anoxic at shallow subsurface depths. Concentrations of Zn, Cu, Pb and Cd were very low or undetectable in the pore waters. There was no evidence of release of Cu, Cd or Pb from the deposited tailings, although there was evidence of possible minor release of Zn from surface sediments in one of the tailings cores. Metals were removed from pore waters below the upper 10 cm at both sites, which is attributed to precipitation of authigenic sulfide phases.

The Laboratory Quality Assurance Component of Environmental Monitoring: A Case Study Involving Subaqueous Tailings Research

“…Both receive tailings from copper-lead-zinc mines. Details covering these studies are presented by Fraser and Robertson (1994) and by Pedersen et al (1994).…”

“…The primary objective of the subaqueous tailings disposal monitoring program is to provide an estimation of the metal fluxes between the sediment and the water. The comprehensive sample coll~ction process is described by Pedersen et al (1994) and was carried out by designated field personnel. The samples collected include sediment cores, lake waters from various depths, and interstitial waters.…”