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Redox-induced speciation changes and reductive mobilization of arsenic, manganese, and iron in highly-contaminated river floodplains

Applicant Kretzschmar Ruben
Number 155890
Funding scheme Project funding (Div. I-III)
Research institution Institut für Biogeochemie und Schadstoffdynamik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Pedology
Start/End 01.01.2015 - 31.12.2015
Approved amount 56'546.00
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All Disciplines (4)

Discipline
Pedology
Mineralogy
Other disciplines of Environmental Sciences
Geochemistry

Keywords (9)

manganese; arsenic; minerals; microbial; floodplain; reduction; soil; oxidation; iron

Lay Summary (German)

Lead
In diesem Projekt erforschen wir grundlegende Mechanismen, die zur Mobilität von As in den pH-neutralen Böden der Ogosta Flussebene beitragen. Arsen liegt in diesen Böden mit schwachkristallinen Eisen(Fe)-(oxyhydr)oxiden in extrem hohen molaren As zu Fe Verhältnissen vor und es gibt eine positive Korrelation zwischen As und Mangan (Mn), das aus Minenabfällen stammt.
Lay summary
Die Flussebene der Ogosta in Nordwest-Bulgarien, eines Seitenarms der Donau, ist durch historische Bergbauaktivitäten mit Arsen belastet. Arsen (As) ist ein toxisches Halbmetall, das die Trinkwasserqualität in vielen Teilen der Welt beeinträchtigt. Seine Bioverfügbarkeit und Löslichkeit ist stark von seiner chemischen Speziierung abhängig, die wiederum vom Boden-pH, wiederkehrenden Überflutungen und der Bodenmineralogie abhängen. Wir konnten zeigen, dass die gut untersuchte Oxidation von As(III) an Mn-Oxiden unter reduzierenden Bedingungen durch eine rasche Fe(II)-Oxidation limitiert ist. Die weiteren Ziele des Projekts sind die Struktur von As-reichen Fe-Phasen zu untersuchen, die einen hohen Einfluss auf die As-Löslichkeit hat, sowie zu zeigen, ob Mn-reiches Bodenmaterial unter reduzierenden Bedingungen eine effektive As Senke darstellen kann.

Die Ogosta ist ein Seitenarm der Donau, dem zweitgrössten Fluss Europas. Die Belastung ihrer Böden bedeutet ein ernstzunehmendes Kontaminationspotential für die Donau. Die Ergebnisse dieses Projekts werden wichtige wissenschaftliche Informationen liefern, die zu einem nachhaltigen Flussgebietsmanagement beitragen.

Direct link to Lay Summary Last update: 22.12.2014

Responsible applicant and co-applicants

Employees

Name Institute

Publications

Publication
Effects of Manganese Oxide on Arsenic Reduction and Leaching from Contaminated Floodplain Soil
Ehlert Katrin Mikutta Christian Kretzschmar Ruben (2016), Effects of Manganese Oxide on Arsenic Reduction and Leaching from Contaminated Floodplain Soil, in Environmental Science&Technology, 50, 9251-9261.

Collaboration

Group / person Country
Types of collaboration
Dr. Tsvetan Kotsev/Bulgarian Academy of Sciences (BAS) Bulgaria (Europe)
- Publication
Synchrotron radiation facilities United States of America (North America)
- Research Infrastructure

Associated projects

Number Title Start Funding scheme
142978 Arsenic contamination of Ogosta river: Linking biogeochemical processes in floodplain soils with river system dynamics 01.11.2012 Bulgarian-Swiss Research Programme (BSRP)
138003 Redox-induced speciation changes and reductive mobilization of arsenic and iron in highly-contaminated river floodplains 01.01.2012 Project funding (Div. I-III)

Abstract

The alluvial floodplains of the Ogosta River in NW Bulgaria, a tributary to the lower Danube River, are highly contaminated with As and other trace elements as a result of historic mining activities. The bioavailability and mobility of As in these floodplain soils is closely linked to its speciation, as influenced by soil pH, recurring flooding events, and soil mineralogy. Due to their alluvial origin, the soils are well stratified and exhibit Mn-oxide enriched layers with considerable variations in terms of elemental composition and degree of As contamination. Although the oxidative attenuation potential of Mn-oxides towards As(III) has been highlighted in a number of laboratory studies, there is a lack of knowledge regarding the impact of Mn-oxides on the mobility of As and Fe in soil under changing redox conditions induced by periodic soil flooding. Therefore, the objectives of our ongoing PhD research were (i) to investigate the distribution of As and other inorganic contaminants along the Ogosta River and the identification of sink-source relationships, and (ii) to elucidate the role of Mn-oxides for the fate of As under microbially reducing conditions.This research extension proposal relates to our ongoing PhD research (1.1.2012-31.12.2014; SNF grant no. 200021_138003) and aims at a better understanding of the mobility of As in floodplains soils characterized by Mn-oxide enriched strata under changing redox conditions. Based on our previous project results, we will test the hypothesis that Mn-oxide-rich soil layers act as a net sink for As under reducing conditions. Therefore, we will explore the influence of Mn-oxides on the speciation changes of As in a representative Ogosta floodplain soil amended with varying levels of Mn-oxides under anoxic conditions. The speciation dynamics of As and associated elements (e.g., Fe and Mn) will be studied by column leaching experiments, aqueous speciation analyses, and reactive transport modeling. Speciation changes of As, Fe and Mn in the solid-phase will be explored by synchrotron-based X-ray absorption spectroscopy as a function of flooding time and flow regime. The results of these experiments will provide scientific information necessary to improve sustainable river management and soil remediation strategies for the Ogosta River floodplain. Thus, in order to meet the research objective outlined in this proposal, we apply for a project extension of another 12 months. This extension will allow us to finalize SNF project 200021_138003, and PhD candidate Katrin Ehlert to complete her theses.
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