Coupling of physical and bio-geochemical processes in saturated and unsaturated subsurface systems.

点击翻译按钮获取中文摘要

The contamination of groundwater from mining, industrial and other anthropogenic activities threatens potable water supplies and ecosystem health. The transport and fate of contaminants in groundwater and in unsaturated soils often involves complex biogeochemical reactions coupled to physical transport and attenuation processes. Reactive transport models provide a means of quantifying these processes, providing a means of analyzing complex data sets and providing insights into the underlying mechanisms of contaminant transport and attenuation. The long-term objectives of the research are to better understand and quantify coupled biogeochemical and physical processes, and the effect of this coupling on contaminant transport and attenuation, through the development of reactive transport models. The key areas for development will include: 1) Simulation of nano-particle and colloid transport and reactivity: Colloids are particles with dimensions measuring in the nano-meter scale. Inorganic and organic colloids can interact with metal-bearing wastes and potentially facilitate their transport in the environment. A reactive transport model will be developed to simulate colloid transport and geochemical interactions, and the model will be used to simulate field and laboratory column experiments to gain a better understanding of colloid-associated metal transport. 2) Simulation of stable isotope fractionation in multi-phase systems: A reactive transport model will be developed to simulate the fractionation of carbon isotopes in methane and carbon in dissolved and vapour phase gases, including gas bubbles. The model will be used to simulate the degradation of contaminants at an oil spill site near the town of Bemidji, MN, providing a better understanding of degradation rates, and transport and attenuation mechanisms. In addition, laboratory tank experiments will be conducted to better quantify the gas/water interactions at the water table. 3) Coupling of physical and geochemical processes in mine waste: The prediction of drainage quality from waste-rock piles is an important aspect of mine planning and permitting. A reactive transport model will be developed to couple thermal, hydrological and geochemical interactions in waste-rock dumps. The model will be applied to data collected at the Diavik Diamond Mine in the Northwest Territories to better understand the processes controlling water quality. 4) Mechanistic simulation of gases and gas bubble movement in contaminated aquifers. A reactive transport model will be developed to provide a better description of gas transport, including the movement of gas bubbles in groundwater. The model will be used to simulate 1) the transport of volatile organic contaminants in groundwater including the vertical transport of gas bubbles due to buoyancy, 2) tritium and organic contaminants in unsaturated materials below and low-level nuclear waste repository, and 3) the entrapment of gas bubbled during recharge below an artificial recharge pond. The proposed research will provide a unique reactive transport model that will provide insight into the movement of contaminants in the subsurface. This insight will aid in the development of cost-effective contaminant stabilization and remediation options that will assist Canadian industry in meeting environmental protection standards. The research will train highly qualified personnel in the development and application of numerical models and provide them with a thorough understanding of contaminant geochemistry and remediation science. These trainees will continue with cutting edge research or will work in industry, managing contamination issues and helping to maintain Canadian companies at the leading edge of the contaminant remediation industry.