Effect of naphtha diluent on greenhouse gases and reduced sulfur compounds emissions from oil sands tailings

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  • The long-term storage of oil sands tailings has resulted in the evolution of greenhouse gases (CH4 and CO2) as a
    result of residual organics biodegradation. Recent studies have identified black, sulfidic zones belowthe tailingswater
    interface, which may be producing toxic sulfur-containing gases. An anaerobicmesocosm study was conducted
    over an 11-week period to characterize the evolution of CH4, CO2 and reduced sulfur compounds (RSCs)
    (including H2S) in tailings as it relates to naphtha-containing diluent concentrations (0.2, 0.8, and 1.5% w/v) and
    microbial activity. Our results showed that RSCswere produced first at 0.12 μmol°RSCs/mLMFT (1.5%w/v diluent
    treatment). RSCs contribution (from highest to lowest) was H2S and 2-methylthiophene N 2.5-
    dimethylthiophene N 3-methylthiophene N thiofuran N butyl mercaptan N carbonyl sulfide, where H2S and 2-
    methylthiophene contributed 81% of the gas produced. CH4 and CO2 production occurred after week 5 at
    40.7 μmol CH4/mLMFT and 5.9 μmol CO2/mLMFT (1.5%w/v diluent treatment). The amount of H2S andCH4 generated
    is correlated to the amount of diluent present and to microbial activity as shown by corresponding increases
    in sulfate-reducers' Dissimilatory sulfite reductase (DsrAB) gene and methanogens' methyl-coenzyme
    M reductase (MCR) gene.

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    Article (Published)
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    Attribution-NonCommercial 4.0 International