DISTRIBUTION AND CHEMICAL SPECIATION OF METALS AND METALLOIDS IN BIOTA COLLECTED FROM CONTAMINATED ENVIRONMENTS BY SPATIALLY-RESOLVED XRF, XANES, AND EXAFS

Shell fragments from turtles collected in a wetland receiving outfall from coal combustion ash basins were elevated in a number of contamina nts, notably Se and As. Micro-XANES analysis of the epithelial layer o n the shell and of the bone tissue revealed that the keratin associate d Se was present exclusively in seleno-amino acid coordination environ ments, whereas Se in the bone tissue was a mixture of selenate and pro teinaceous Se, Elemental distribution maps of hyperaccumulating plants generated by XRF reveal a heterogeneous distribution of Se and Cr, wi th Se being concentrated within the nuclei of cells and Cr within disc rete aggregates in the cytoplasm. Micro-XANES measurements taken on th ese same regions demonstrated the total loss of the Cr(VI) diagnostic pre-edge feature, indicating the complete reduction of the Cr(VI) to C r(III) after uptake by the plants.