Environmental studies of iron in sediments by means of X-ray absorption spectroscopy

Abstract

X-ray Absorption Fine Structure (XAFS) spectroscopy was used to identify directly the metal speciation and local bonding environment of Fe in sediments originated from Dobczyce reservoir (Poland); special attention was paid to analysis of samples collected from points situated at different distances from the land. The combination of traditional approach to data analysis as well as usage of multivariate techniques provided reliable information on the local Fe structure. The obtained average oxidation state for Fe species in all samples was found to be at about +3. The number, nature, and proportion of Fe species in sediments samples were calculated by a coupled Principal Component Analysis (PCA) and Least-Squares Fitting (LSF) procedure. Results indicate for a high similarity among analyzed data collected for various points from Dobczyce reservoir. Among different forms of amorphous oxyhydroxides and various iron oxides commonly present in lake sediments, hematite (Fe2O3) and goethite (α-FeOOH) were found to be the dominant crystalline structures in analyzed samples. Based on that finding it can be concluded that Fe is principally bound to oxygen in sediment samples, therefore its (re)mobilization to the water may be neglected.