| 1. |
- Dekov, Vesselin, et al.
(author)
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Ferrihydrite precipitation in goundwater-fed river systems (Nete and Demer river basins, Belgium): Insights from a combined Fe-Zn-Sr-Nd-Pb-isotope study.
- 2014
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In: Chemical Geology. - : Elsevier. - 0009-2541 .- 1872-6836. ; 386, s. 1-15
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Journal article (peer-reviewed)abstract
- Two groundwater-fed river systems (Nete and Demer, Belgium) carry red suspended material that settles on the river bed forming red sediments. The local aquifer that feeds these river systems is a glauconite-rich sand, which provides most of the dissolved Fe to the rivers. The solid component of these systems, i.e., the red suspended material and sediments, has a simple mineralogy (predominantly ferrihydrite), but shows a complex geochemistry pointing out the different processes contributing to the river chemistry: (1) the red sediments have higher transition metal (excluding Cu) and detrital element (e.g., Si, Al, K, Rb, etc.) concentrations than the red suspended matter because of their longer residence time in the river and higher contribution of the background (aquifer) component, respectively; (2) the red suspended material and sediments have inherited their rare earth element (REE) patterns from the aquifer; (3) the origin of Sr present in the red suspended matter and red sediments is predominantly marine (i.e., Quaternary calcareous rocks), but a small amount is geogenic (i.e., from detrital rocks); (4) Pb in both solids originates mostly from anthropogenic and geogenic sources; (5) all of the anthropogenic Pb in the red suspended material and sediments is hosted by the ferrihydrite; (6) Nd budget of the red riverine samples is controlled by the geogenic source and shows little anthropogenic component; (7) the signi- ficant Fe- and Zn-isotope fractionations are in line with the previous studies. Their fractionation patterns do not correlate, suggesting that the processes controlling the isotope geochemistry of Fe and Zn are different: oxidation/reduction most likely governs the Fe-isotope fractionation, whereas adsorption/desorption or admixing of anthropogenic sources controls the isotope fractionation of Zn.
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| 2. |
- Kovács, Krisztina, et al.
(author)
-
Mössbauer study of synthetic jarosites
- 2008
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In: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540. ; 186:1-3, s. 69-73
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Journal article (peer-reviewed)abstract
- 57Fe Mössbauer spectroscopy and PXRD were used to study artificially prepared jarosites with the compositions of KFe3(SO4)2(OH)6 - x F x x = 0 - 1.6 PXRD measurements revealed single phase jarosite samples. All Mössbauer spectra taken at room temperature exhibit a quadrupole doublet corresponding to mineral jarosite. However, at low temperature where the mineral jarosite has a well resolved sextet, the synthetic jarosite even with x = 0 F - content shows a relaxation transition. The spectra indicate that with increasing F - concentration, the paramagnetic-antiferromagnetic transition temperature is decreasing. The results can be used in the analysis of artificial jarosites or those formed during biomineralization processes.
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