Characterizing in situ remediation strategies for metal contaminated soils

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Elevated trace metal concentrations are a common occurrence in surface soils around many industrial and mining sites, in shooting ranges, and in sites that have received repeated applications of biosolids. Although stringent regulations have helped reduce such contamination, legacy contaminants remain a significant threat to human and ecological health. Current remediation technologies, such as soil excavation, are costly and may not be applicable on a field scale. Additionally, approaches that employ phosphorus (P) to stabilize metals such as lead (Pb) may present environmental risk (eutrophication) to surface waters. The overall objective of this proposed research program is to identify critical mechanisms regulating the performance of in situ remediation approaches - phytoremediation and chemical stabilization - for Pb-contaminated soils. An understanding of the processes and mechanisms will allow improvement of the technologies to speed up cleanup while minimizing leaching to groundwater. A series of greenhouse, laboratory, and field experiments will be performed to (i) characterize the efficacy of Indian mustard and corn for phytoremediation of Pb-contaminated sites; (ii) understand the change in contaminant dynamics when EDTA is applied to enhance Pb phytoextraction in calcareous soils; (iii) study the interaction of Pb with fertilizer or compost P in the presence of EDTA; (iv) determine Pb and P fractionation in contaminated soils treated with EDTA and/or manure phosphorus; (v) identify the dominant processes influencing the mobility of EDTA-bound Pb in the root zone; (vi) characterize the basic mechanisms controlling chemical stabilization of Pb using P derived from fertilizer or compost, and (vii) identify the mechanisms regulating Pb and phosphorus leaching in P-treated Pb-contaminated soils. Results from the research will enhance our understanding of the fundamental processes involved in these remediation approaches and help improve their field perfomance. Models formulated from the research will also assist government and industry in the site-specific assessment of potential success and risks of the remediation strategies based on site characteristics.