In-Place Inactivation of Pb in Pb-Contaminated Soils

There has been increasing attention to the use of soil amendments and green plants to remediate surface soils contaminated with Pb. We call one form of this technique in-place inactivation. In-place inactivation reduces the hazards associated with contaminated soils through the use of chemicals that change the molecule species of the Pb to stabilize the soil Pb chemically and physically in situ. We have seen significant changes in soil Pb chemistry, Pb leached from soil, and Pb measured by a physiologically based extraction test (PBET) after incorporating inexpensive and readily available materials to three soils. The soils have total Pb concentrations that range from 1200 to 3500 mg kg-1. The leachable soil Pb was significantly reduced in all cases from as high as 30 mg Pb L-1 to below the regulatory limit of 5 mg Pb L-1 after soil treatment. The PBET mimics the mammalian gastric−intestinal tract solutions. In the simulated intestinal phase of the PBET, Pb in solution was reduced by 72% in one of the soils treated with a high Fe-containing industrial byproduct. These results help to illustrate the utility of incorporating soil amendments to reduce hazards associated with Pb-contaminated soils.