Universität zu Köln

Dorau, Kristof ORCID: 0000-0002-1815-1929 and Mansfeldt, Tim ORCID: 0000-0002-7557-6827 (2016). Manganese and iron oxide-coated redox bars as a tool to in situ study the element sorption in wet soils. J. Soils Sediments, 16 (3). S. 976 - 987. HEIDELBERG: SPRINGER HEIDELBERG. ISSN 1614-7480

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Abstract

When studying redox conditions in soils with manganese (Mn) and iron (Fe) oxide-coated redox bars, we observed the formation of Fe oxides along the Mn oxide coating and assumed sorption of other elements from soil solution to oxide surface. The objective of this study was to investigate the formation of Fe oxides along Mn redox bars and to analyze element sorption from soil solution to either Mn or Fe oxide along redox bar coatings. We protruded Mn redox bars into solutions with defined Fe2+ concentrations and removed the bars at distinct time intervals. The Mn oxide coating and potential Fe oxides were extracted using dithionite-citrate-bicarbonate (DCB). To investigate in situ element sorption behavior, we used previously field-installed redox bars, protruding these Mn redox bars into acidified hydroxylamine hydrochloride (AAH) to selectively extract Mn oxide and afterwards into DCB to dissolve the remaining Fe oxide coating. This two-step extraction procedure enabled the differentiation of elements bonded to either Mn or Fe oxide. Additionally, we analyzed the redox bar coatings at a very small scale (< 1 mm(2)) via energy-dispersive x-ray spectroscopy (EDX). Iron oxides precipitated along the Mn oxide coating at low concentrations of 0.05 mg Fe2+ L-1, but did not trigger a color change. Although a change in color did occur instantaneously at 500 mg Fe2+ L-1, it is expected that Fe2+ concentrations are significantly lower under field conditions because ferrous Fe auto-oxidized within the artificial setup. Whereas Mn oxide sorbed cationic elements from the soil solution in the order Cu > Pb > Zn, Fe oxide preferentially sorbed oxyanions with As > P > Mo > V, respectively. Field-Fe oxides precipitating along the Mn redox bars sorbed elevated levels of As and P compared with the action of synthesized lab-Fe oxides along Fe redox bars, a finding which we attribute to short-range-ordered Fe phases with elevated sorption capacity. Besides providing information regarding the monitoring of soil redox status, the developed sequential two-step extraction procedure enables the differentiation of the selective sorption of elements in the soil solution to the coating of Mn and Fe redox bars. The collection of Fe oxides formed naturally along the Mn redox bar coatings further enables the investigation of temporally and spatially diverse Fe oxide-forming processes.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Dorau, Kristof UNSPECIFIED orcid.org/0000-0002-1815-1929 UNSPECIFIED Mansfeldt, Tim UNSPECIFIED orcid.org/0000-0002-7557-6827 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-283346
DOI:	10.1007/s11368-015-1300-6
Journal or Publication Title:	J. Soils Sediments
Volume:	16
Number:	3
Page Range:	S. 976 - 987
Date:	2016
Publisher:	SPRINGER HEIDELBERG
Place of Publication:	HEIDELBERG
ISSN:	1614-7480
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Geosciences > Geographisches Institut
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language ISOTOPE FRACTIONATION; WATERLOGGED SOIL; ZINC SPECIATION; HEAVY-METALS; ADSORPTION; TRANSFORMATION; REDUCTION; LEAD; DISSOLUTION; MOLYBDENUM Multiple languages Environmental Sciences; Soil Science Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/28334