You are here:
EVALUATION OF EXTRACTION AND SPECTROSCOPIC METHODS FOR PB SPECIATION IN AN AMENDED SOIL
Citation:
Scheckel*, K G., C A. Impellitteri**, AND J A. Ryan*. EVALUATION OF EXTRACTION AND SPECTROSCOPIC METHODS FOR PB SPECIATION IN AN AMENDED SOIL. Presented at Annual Meetings of the American Society of Agronomy, Denver, CO, 11/2-7/2003.
Description:
Immobilization of pyromorphite (Pbs(PO4hCI) via P amendments to Pb contaminated soils is proving to be a viable method of remediation. However, the issue of ascertaining the amount of soil Pb converted to pyromorphite is difficult in heterogeneous soil systems. Previous attempts by selective sequential extraction (SSE) demonstrated that a significant portion of the soil Pb was in the residual fraction; assumed to be the fraction associated with pyromorphite. Yet, recent research has shown that the rapid formation of pyromorphite can occur in the least aggressive first step (and presumably other steps) of SSE due to release of Pb and P during extraction suggesting that a considerable share of the pyromorphite in the residual fraction is the result of pyromorphite precipitation during the SSE procedural steps. Our research compares the results of an operationally defined SSE procedure relative to synchrotron-based X-ray absorption fine structure (XAFS) spectroscopic experiments coupled with quantitative linear combination fitting (LCF) analysis. The data show that pyromorphite content in the XAFS samples was much lower than the results gathered for the residual fraction of the SSE method. The results indicate that SSE may over predict the amount of pyromorphite formed in P-amended Pb-contaminated soils and that rigorous interpretation of SSE results should be avoided.