Phosphorus and Manganese Oxides Effects on Soil Lead Bioaccessibility: PBET and TCLP

Abstract

Lead (Pb) is toxic to humans, especially to young children, as well as animals. Toxicity is strongly related to the bioavailability of Pb and soil Pb bioavailability can be influenced by soil amendments. This study was conducted to evaluate the effects of Mn oxides and phosphorus (P) on Pb bioaccessibility in five lead-contaminated soils or mine spoils from Kansas and Missouri, USA. Fifteen treatments were used: Brazilian (BMN) and Amonone #4 (AM#4) (commercial Mn oxides), birnessite (BIR) and cryptomalene (CRYP) (synthetic Mn oxides), phosphate rock (PR) and triple superphosphate (TSP) phosphorus sources, and combinations of each P source with the Mn oxides. A physiologically based extraction test (PBET) was used to evaluate time and treatment effects. All amendments significantly decreased Pb bioaccessibility compared with control although treatment effects differed from soil to soil. In general, TSP, PR, and BIR treatments were most effective in decreasing Pb. Some amendments reduced the toxicity characteristic leaching procedure (TCLP) concentration for Pb to below the critical value of 5 mg L−1, but were not able to reduce TCLP extractable Cd to below 1 mg L−1. Our results indicated that the use of P and Mn oxides for reducing soil Pb bioaccessibility in contaminated soils is promising.