In-situ metal speciation in soils using synchrotron based techniques

Contamination of the environment resulting from anthropogenic activities such as mining, smelting and agriculture is of great public and political concern. As such, a greater understanding of the mobility, bioavailability and long-term fate of the materials resulting from these activities is needed in order to make more accurate decisions when devising remediation and legislative strategies. To provide an accurate description of the fate of metal contaminants in heterogeneous systems, it is essential to understand their speciation. Macroscopic chemical analyses are not sufficient and hence must be complemented with advanced molecular scale techniques. Synchrotron based micro xray fluorescence and extended x-ray absorption (!-SXRF, !-EXAS) spectroscopies provide the needed selectivity by allowing one to probe, in-situ, the local coordination environment of a species over a wide range of concentrations in homogeneous and heterogeneous environments. The resultant structural information provides a mechanistic understanding of the processes controlling the fate of contaminants under environmentally relevant conditions. Current research conducted at the ALS by our group has focused on the application of !-EXAS and !-SXRF techniques at beamline 10.3.2 to investigate the speciation of zinc (Zn), nickel (Ni), and arsenic (As) in contaminated soils.