HR: 15:15h
AN: B23C-07 INVITED     [Abstracts]
TI: Seasonal and spatial variations of microbial sulfate and iron reduction in alkaline Pb-Zn mine tailings (Ontario, Canada)
AU: * Fortin, D
EM: dfortin@uottawa.ca
AF: Danielle Fortin University of Ottawa, 140 Louis Pasteur, Ottawa, ON K1N 6N5 Canada
AB: Both microbial iron and sulfate reduction are being investigated as potential processes capable of combating acidity and promoting heavy metal precipitation in mining environments. Several studies have shown that sulfate-reducing bacteria (SRB) are active in acidic sulfide-rich mine tailings and acidic sediments and promote metal sulfide precipitation. SRB activity in these acidic tailings has been shown to vary with seasons as a result of fluctuating in situ physico-chemical conditions. Iron-reducing bacteria (FeRB) also play an important role in iron cycling in sediments impacted by mining activities, but their activity is often limited by the availability of electron donors and electron acceptors. Interestingly, very little is known about the activity of FeRB in mine tailings, but geochemical evidence point to the fact that they might be active and potentially competing with SRB for common electron donors. The present study was undertaken to assess the temporal and seasonal changes in SRB and FeRB activity in alkaline Pb-Zn mine tailings (Calumet tailings) located near Ottawa, ON, Canada. Results showed that both FeRB and SRB populations were present throughout the year at 2 different sampling sites at the Calumet tailings and that their activity was affected by organic carbon availability at each site. Surface agricultural runoff at one site provided ample nutrients and organic carbon that promoted FeRB activity over SRB activity throughout the year, whereas the second site (not impacted by nutrient runoff) showed increased SRB activity over FeRB activity. This indicates that the type and source of available electron donors in mine tailings has a direct impact on the activity of SRB and FeRB. Interestingly, temperature did not appear to hinder SRB and FeRB activity in alkaline tailings, as previously observed in acidic mine tailings and increasing sulfate-reduction rates over the course of the year did not correspond to lower sulfur isotopic values of the chromium reducible sulfide (CRS) fraction.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
SC: Biogeosciences [B]
MN: Fall Meeting 2005