Monday, November 13, 2006

Long-Term Bioavailability of Phosphate-Immobilized Metals in Contaminated Urban Soil.

Xi Tang, Univ of Missouri, Dept of Soil, Env, and Atmos Sciences, 321 ABNR Building, Columbia, MO 65211-7250, John Yang, Lincoln Univ, 310 Foster Hall, Jefferson City, MO 65102, and Keith Goyne, University of Missouri, University of Missouri, 302 ABNR Bldg, Columbia, MO 65211-7250.

In-situ soil treatment using phosphates is being evaluated as a cost- effective remedial technology for immobilizing soil metals and reducing health and ecological risks. A long-term assessment of risk reduction by treatment and stability of phosphate-immobilized metals is needed to verify efficacy and gain regulatory and public acceptance of the phosphate-based remedial technology. A smelter-contaminated urban soil in the Jasper County Superfund Site, Southwestern Missouri, was treated in the field with phosphoric acid at three rates using three different application methods. Soil, plant, and water samples were collected 8 yr after treatment from experimental plots and analyzed for in-vitro bioavailability, phyto-availability, microbial toxicity, and leachable metals. Preliminary data verifies that phosphate treatment is effective for reducing human and ecological risk 8 yr after initial treatment. Thus, the data are indicative of relative metal phosphate stability in treated soils. Immobilization induced by phosphate treatments lowers metal solubility in soil and reduces threats to humans, plants, microorganisms, and water resources.