Geochemical Behaviour of Submerged Pyrite-Rich Tailings in Canadian Lakes

Abstract

Sulphide-rich mine tailings have been discharged to marine and lacustrine waters in many parts of the world for centuries, often with little regard for potential long-term chemical consequences. Somewhat fortuitously, this strategy may have limited overall environmental impact, because recent evidence suggests that chemical reactivity of tailings is in fact inhibited by storage underwater. Pedersen et al. (1993) showed, for example, that fresh pyrite-rich tailings discharged to Anderson Lake, Manitoba, did not release metals to the overlying water column, at least in the summer season. Similarly, pore water studies conducted more that a decade ago in pyrite and chalcopyrite-bearing tailings on the floor of a British Columbian fjord (Pedersen 1985) revealed that excess copper was not released from the submerged deposits, at least during the period shortly after deposition. Such studies imply that the permanent storage of sulphide-rich tailings underwater offers considerable promise as a technology to inhibit to a very large degree the release of acid and metals from such materials to the environment.