Managing Pb Contaminated Urban Soils Using Low Rates of P Amendments.

Managing soils in urban areas containing elevated levels of soil Pb continues to be an active area of concern due to the public health impacts of elevated blood lead levels. Treating soils with phosphate amendments has been demonstrated to bind up Pb within Pb-phosphate minerals and reduce in-vitro bioaccessible (IVBA) Pb.  Previous rates utilized include 10,000 mg P kg^-1 soil (1% P).  This application rate used phosphoric acid to add P to the soil and reduce soil pH to increase soil Pb solubility.  Concerns have been raised about these application rates of P to soils, particularly due to P runoff concerns in areas close to water bodies.  Rather than using phosphoric acid to reduce soil pH, this study evaluated using lower P application rates (0.5 g P kg^-1 soil) and used other methods to reduce soil pH.  Soil treatments included bone meal and triple super phosphate on a soil containing approximately 800 mg Pb kg^-1 soil.  Reductions in IVBA Pb were measured using USEPA Method 1340 (pH 1.5 with 0.4 M glycine) and additional in-vitro methods.  Other methods included using the modified physiologically-based extraction test (PBET) used by Attanayake et al. (2014).  This study provides novel data about using lower rates of P-amendments to remediate Pb-contaminated soils.