Distribution and Chemical Speciation of Metals and Metalloids in Biota Collected from Contaminated Environments by Spatially Resolved XRF, XANES, and EXAFS

Abstract

Shell fragments from turtles collected in a wetland receiving outfall from coal combustion ash basins were elevated in a number of contaminants, notably Se and As. Micro-XANES analysis of the epithelial layer on the shell and of the bone tissue revealed that the keratin associated Se was present exclusively in seleno-amino acid coordination environments, whereas Se in the bone tissue was a mixture of selenate and proteinaceous Se. Elemental distribution maps of hyperaccumulating plants generated by XRF reveal a heterogeneous distribution of Se and Cr, with Se being concentrated within the nuclei of cells and Cr within discrete aggregates in the cytoplasm. Micro-XANES measurements taken on these same regions demonstrated the total loss of the Cr(VI) diagnostic pre-edge feature, indicating the complete reduction of the Cr(VI) to Cr(III) after uptake by the plants.