Microbial communities in tailings covered with a cover system comprising of a layer of carbon-rich material and a layer of desulfurized tailings

The Strathcona Waste Water Treatment System (SWWTS), located in the Ni/Cu mining and milling complex (Sudbury, ON, Canada), received tailings from ore processing from 1970 to present. Demonstration-scale, multi-layer cover systems were installed at SWWTS in selected cells. The cover systems comprise an upper layer of organic carbon-rich material (biosolids, composted municipal food and yard waste), and a layer of desulfurized tailings. Organic carbon promotes microbial communities that consume O2, thus decreasing sulfide oxidation rates. The aim of this study was to investigate microbial diversity in tailings recovered from the site and assess the impact of the organic component of the cover system four to six years after application. High-throughput amplicon sequencing of 16S rRNA genes indicated no increase in richness or shifts in BACs in samples collected from the covered sites.