Environmental Studies of Iron in Sediments by Means of X-ray Absorption Spectroscopy

Document Type: Original Research Paper

Authors

1 Singapore Synchrotron Light Source (SSLS), National University of Singapore (NUS), 5 Research Link, Singapore

2 ISS / ANKA Light Source, Forschungszentrum Karlsruhe, Germany, Hermann-von-Helmholtz- Platz 176344 Eggenstein-Leopoldshafen, Germany

3 Singapore Synchrotron Light Source (SSLS), National University of Singapore (NUS), 5 Research Link, Singapore, Physics Department, NUS, 2 Science Drive 3, Singapore

4 Institute of Nuclear Physics PAN, ul Radzikowskiego 152, 31-342 Krakow, Poland

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.

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