Skip to main content
Research article - Peer-reviewed, 2013

Characterisation of hydrous ferric oxides derived from iron-rich groundwaters and their contribution to the suspended sediment of streams

Baken, Stijn; Sjostedt, Carin; Gustafsson, Jon Petter; Seuntjens, Piet; Desmet, Nele; De Schutter, Jan; Smolders, Erik

Abstract

When Fe(II) bearing groundwaters surface in streams, particulate authigenic Fe-rich material is produced by oxidation. Such freshly precipitated Fe minerals may be transported as suspended sediment and have a profound impact on the fate of trace metals and nutrients in rivers. The objective of this study was to monitor changes in mineralogy and composition of authigenic material from its source to streams of increasing order. Groundwaters, surface waters, and suspended sediment in streams of different order were sampled in the Kleine Nete catchment (Belgium), a lowland with Fe-rich groundwaters (3.5-53.8 mg Fe/L; pH 6.3-6.9). Fresh authigenic material (>0.45 mu m) was produced by oxidising filtered (<0.45 mu m) groundwater and surface water. This material contained, on average, 44% Fe, and smaller concentrations of C, P, and Ca. Iron EXAFS (Extended X-ray Absorption Fine Structure) spectroscopy showed that the Fe was present as poorly crystalline hydrous ferric oxides with a structure similar to that of ferrihydrite. The Fe concentration in the suspended sediment samples decreased to 36-40% (stream order 2), and further to 18-26% (stream order 4 and 5). Conversely, the concentrations of organic C, Ca, Si, and trace metals increased with increasing stream order, suggesting mixing of authigenic material with suspended sediment from a different source. The Fe speciation in the suspended sediment was similar to that in fresh authigenic material, but more Fe-Fe interactions were observed, i.e. it was increasingly hydrolysed, suggesting ageing reactions. The suspended sediment in the streams of order 4 and 5 is estimated to contain between 31% and 59% of authigenic material, but more data are needed to refine this estimate. The authigenic material is an important sink for P in these streams which may alleviate the eutrophication risk in this catchment. (C) 2013 Elsevier Ltd. All rights reserved.

Published in

Applied Geochemistry
2013, volume: 39, pages: 59-68
Publisher: PERGAMON-ELSEVIER SCIENCE LTD

Authors' information

Baken, Stijn
University of Leuven (KU Leuven)
Royal Institute of Technology (KTH)
Swedish University of Agricultural Sciences, Department of Soil and Environment
Seuntjens, Piet
VITO
Desmet, Nele
VITO
De Schutter, Jan
Flanders Hydraulics Research
Smolders, Erik
University of Leuven (KU Leuven)

UKÄ Subject classification

Environmental Sciences
Geochemistry

Publication Identifiers

DOI: https://doi.org/10.1016/j.apgeochem.2013.09.013

URI (permanent link to this page)

https://res.slu.se/id/publ/51207