Characterisation of zinc in slags originated from a contaminated sediment by coupling mu-PIXE, mu-RBS, mu-EXAFS and powder EXAFS spectroscopy

Depositing dredged sediments on soils is usual but it is a hazardous practi ce for the local environment when these sediments are polluted by heavy met als. This chemical hazard can be assessed by determining the speciation of metals. In this study, slags highly polluted with Zn and originated from a contaminated dredged sediment were investigated. Zn speciation was studied by laterally resolved techniques such as mu -particle induced X-ray emissio n (mu -PIXE), mu -Rutherford backscattering spectrometry (V-RBS), p-extende d X-ray absorption fine structure (p-EXAFS), and bulk analyses such as powd er EXAFS spectroscopy. mu -PIXE and mu -RBS results showed that high concen trations of Zn were associated with S in localised areas at the surface of the slags while moderate amounts of Zn were mainly associated with Fe in th e matrix. EXAFS results allowed to identify ZnS and Zn sorbed on ferrihydri te (5Fe(2)O(3). 9H(2)O), proxy for iron oxy-hydroxides, as the main Zn-bear ing phases. The occurrence of this Zn-iron oxy-hydroxide is interpreted as a mobilisation. of Zn released from ZnS oxidation. (C) 2001 Elsevier Scienc e B.V. All rights reserved.