Acid Generation and Metal Immobilization in the Vicinity of a Naturally Acidic Lake in Central Yukon Territory, Canada

Abstract

Sulphide oxidation in mine waste is one of the primary causes of anthropogenic production of acid lakes and drainage (Geller et al., this Vol.). In addition to the toxic effects of acid itself, the environmental hazards of acid drainage rest with the commonly elevated content of dissolved heavy metals (Allard et al. 1987; Blowes and Jambor 1990; Axtmann and Luoma 1991; Alpers et al. 1994; Deniseger and Kwong 1996). These metals may be released directly from the sulphides upon oxidation or derived indirectly by acid leaching of the associated geologic materials. Sulphide oxidation is, however, also a natural weathering process which can lead to the occurrence of natural acid drainage in the absence of mining activities (van Everdingen et al. 1985; Kwong and Whitley 1993). By studying a natural acid drainage system, one can better understand the various factors controlling acid generation in sulphide-rich material and the metal attenuation mechanisms occurring in nature. In turn, one can apply the relevant knowledge in devising appropriate strategies for the abatement of acidification and metal contamination in mining lakes. It is the purpose of this chapter to document the observations made in the vicinity of a naturally acidic lake in central Yukon Territory, Canada. Field observations coupled with analyses on water chemistry, sediment geochemistry and microbiology of a suite of water and sediment samples are used to explain the acid generation and metal immobilization processes occurring at the site. The implications of the findings for rehabilitating acidic mining lakes in general are briefly discussed.