Methylmercury (MeHg) production is magnified in the natural environment by geochemical influxes and an active sulfate reducing bacteria community. It has been found that the presence of sulfides, excess nutrients, and the type of depositional environment (normal marine or euxinic) greatly influences MeHg production and degree of pyritization (DOP). The aim of this research is to investigate a possible connection between MeHg accumulation and the DOP in Weeks Bay sediment. Collected sediment samples have confirmed a significant presence of total reduced sulfides, inorganic mercury, reactive iron, and total organic carbon. Pyritization results indicate a normal marine environment and, of the three measured elements (S, Fe, and C,) carbon and sulfur are the dominant limiting factors to the DOP in Weeks Bay. Current geochemical and pH/redox conditions favor MeHg and pyrite production. The quantified pyrite greatly exceeds that of MeHg indicating DOP inhibits MeHg precipitation.

Dicamba is often tank mixed with glyphosate to increase herbicidal efficacy but may contribute to off-target movement (OTM). In recent years, volatilization has become problematic for dicamba-containing herbicides, resulting in increased regulatory requirements necessitating the use of volatility-reducing agents (VRA) for application. Research was conducted in 2021 and 2022 using low tunnels in a field environment and humidomes in a greenhouse environment to further assess how glyphosate salts and VRAs affect dicamba volatility. Our data indicate that the inclusion of glyphosate to dicamba can increase dicamba volatility, depending on the glyphosate salt used. The inclusion of the evaluated VRAs will decrease dicamba volatility when applied to a tank mixture of dicamba plus potassium salt of glyphosate.

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Due to the very long half-life of Se-79 and its presence in used nuclear fuel, Se is an element of interest in the safety assessment for a deep geological repository (DGR) for used nuclear fuel. Sorption of radionuclides onto the surrounding host rocks and engineered barrier materials is a potential retardation mechanism for radionuclide transport. This thesis investigates the sorption of Se(-II) onto illite, bentonite (engineered barrier material), and shale under high ionic strength conditions relevant to a Canadian DGR. The ionic strength and pH dependence of Se(-II) sorption onto illite, bentonite, and shale were studied. A non-electrostatic surface complexation model was also developed for Se(-II) sorption onto illite and montmorillonite to investigate the sorption mechanisms by which Se(-II) sorbs onto these solids. / Thesis / Master of Applied Science (MASc)

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