Stanley, Nicolette2013-11-072013-11-0720052005Source: Masters Abstracts International, Volume: 44-04, page: 1779.http://hdl.handle.net/10393/27043http://dx.doi.org/10.20381/ruor-18509Mercury is a well known environmental pollutant. Anthropogenic sources include coal combustion, waste incineration and metal processing. In base metal mines, Hg is often left in the mining wastes (i.e., mine tailings). Once disposed of in open-air impoundments, these Hg-containing tailings can undergo various biogeochemical transformations, including Hg methylation. It is the methylated form of mercury (MeHg) that poses a threat to the environment, because it bio-accumulates at each level of the food chain. The present study was undertaken to assess the biogeochemical factors affecting Hg methylation in Cu-Zn and Au mine tailings. The study focused on the role of sulfate-reducing bacteria (SRB) because they are suspected to be associated with Hg methylation. Temperature, sulfate and organic carbon availability, along with SRB activity were tested as potential factors affecting Hg methylation in column experiments containing old Au tailings and fresh Cu-Zn tailings. The results first showed that SRB activity did not enhance Hg methylation in Cu-Zn tailings and Au tailings, indicating that iron reducing bacteria, and not SRB, along with abiotic methylation reactions played an important role. Cold temperatures did not slow down SRB activity and MeHg production, but the accidental freezing and thawing of the Cu-Zn tailings promoted the production of soluble MeHg. The mechanism responsible for this unexpected Hg methylation is however unknown. Elevated organic carbon and sulfate concentrations did enhance SRB activity, but not MeHg formation in the tailings, because increased sulfide production hindered Hg methylation. Tailings mineralogy played a significant role in the production of methyl mercury, Au tailings contained more soluble and solid-bound MeHg than Cu-Zn tailings. These results add to the increasing amount of information on Hg cycling in the environment, and indicate that SRB might not be the dominant Hg methylators in mining environments.157 p.enBiogeochemistry.Thesis