|Mine Waste Technology Program, Linking Waterfowl with Contaminant Speciation in Riparian Soils (EPA/600/R-08/060) January 2008|
This report summarizes the results of Mine Waste Technology Program (MWTP) Activity III, Project 38, Linking Waterfowl with Contaminant Speciation in Riparian Soils, implemented and funded by the U.S. Environmental Protection Agency (EPA) and jointly administered by EPA and the U.S. Department of Energy. This project addressed EPA’s technical issue of Mobile Toxic Constituents – Water and Acid Generation.
Soil samples were collected from the Coeur d’Alene river basin and were analyzed for mineralogy and metal contaminant speciation. Both phosphorus (P)-treated soils and untreated soils were examined to determine the effect of P-amendment on metal speciation. Previous studies suggested P-amendments result in precipitation of poorly soluble lead (Pb) phosphate minerals. In this study, P appears to associate with iron-bearing minerals in the soil, whereas Pb associates predominantly with manganese-bearing phases.
The research conducted on site mineralogy and speciation generated no irrefutable evidence that P-amendments promoted formation of poorly soluble Pb-P mineral phases. In theory, such phases would lower Pb bioavailability in waterfowl exposed to Pb-contaminated soils and sediments. Thus, development of a screening-level method for assessing P-treatment effectiveness (and subsequent reduction in Pb bioavailability) becomes a critical issue.
This need is addressed by the two-step sequential extraction procedure that simulates the gizzard and intestinal phases of a typical waterfowl’s gastrointestinal tract. Dr. Strawn’s approach is a modified version of the physiologically based extraction test (PBET) for estimating Pb bioaccessibility in humans and is subsequently called W-PBET. The gizzard phase of this test demonstrated high Pb extraction reproducibility and accuracy. The Pb bioaccessibility results were positively correlated with those from waterfowl fed contaminated and in situ-treated soils from the lower Coeur d’Alene river basin. Therefore, W-PBET is a promising, cost-effective method for initial assessment of site-specific Pb bioavailability in waterfowl.
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