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DETERMINING SPECIATION OF PB IN PHOSPHATE AMENDED SOILS: METHOD LIMITATIONS
Citation:
Scheckel*, K G., J A. Ryan*, D Allen*, AND N. V. Lescano. DETERMINING SPECIATION OF PB IN PHOSPHATE AMENDED SOILS: METHOD LIMITATIONS. J. O. Nriagu (ed.), SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier Science BV, Amsterdam, Netherlands, 350(1-3):261-272, (2005).
Description:
Determining the effectiveness of in-situ immobilization for P-amended, Pb-contaminated soils has typically relied on non-spectroscopic methods that in recent years have come under scrutiny due to technical and unforeseen error issues. In this study, we analyzed 18 soil samples via X-ray diffraction (XRD), selective sequential extraction (SSE), and a physiologically based extraction test (PBET) and compared the results against each other and to previous data collected for the soil samples employing X-ray absorption fine structure spectroscopy coupled with linear combination fitting (XAFS-LCF) that spectroscopically speciated and quantified the major Pb species in the samples. It was observed that XRD was incapable of detecting pyromorphite, the hopeful endpoint of the immobilization strategy. Further, the SSE and PBET extraction methods demonstrated an increase of recalcitrant Pb in comparison to the XAFS-LCF results suggesting that SSE and PBET methods induced the precipitation of pyromorphite during the extraction procedures. The theme of this paper illustrates the experimental concerns of several commonly employ methods to investigate amended, metal-contaminated systems which are not in true equilibrium. The application of spectroscopic methods will provide more conclusive and accurate results as in our study and related environmental systems (i.e., Ni, Cd, etc) where P-induced immobilization is and has been examined.