Fate of trace contaminants at waste sites

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The release of inorganic and organic contaminants from wastes sites can lead to the deterioration of groundwater used for water supply and discharge of contaminants to surface water bodies. The release and transport of contaminants from source zones vary spatially and temporally depending on a complex combination of physical and geochemical processes. At some sites, the highest concentrations of contaminants are released during the first few decades of waste disposal, whereas at other sites, many decades will pass before the highest concentrations are observed. Contaminants can be transported several kilometers at some sites, whereas at others the distance of contaminant migration might be limited to only 10s of meters. This research program is directed at quantifying the physical and geochemical processes controlling the long-term release of contaminants from solid and liquid waste sites. Hydrogeological and geochemical studies will be carried out at old mine and refinery waste sites. These sites are often characterized by very high concentrations of dissolved metals, in excess of 10,000 mg/L, which can be released over many decades after waste disposal ceases. Laboratory and field measurements of physical water and gas transport processes and water, gas and solid phase geochemical reactions will be made. These results will be used to refine computer models to develop long-term predictions of contaminant transport. A second component of the research program will focus on physical and geochemical processes controlling contaminant transport from wastewater disposal sites. Wastewater from domestic, agricultural, and commercial sources is routinely disposed of in tile-beds or by other means and allowed to infiltrate into the subsurface leading to the development of large plumes of contaminated groundwater. The transport of major and trace contaminants, including pharmaceutical compounds, personal care products, and pathogens, will be evaluated in context of the overall plume chemistry. The understanding of the above processes is a fundamental aspect of the development of effective and long-term remediation schemes for contaminated solid and liquid waste sites.