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Redox Heterogeneities Promote Thioarsenate Formation and Release into Groundwater from Low Arsenic Sediments

Title data

Kumar, Naresh ; Noël, Vincent ; Planer-Friedrich, Britta ; Besold, Johannes ; Lezama-Pacheco, Juan ; Bargar, John R. ; Brown, Gordon E. ; Fendorf, Scott ; Boye, Kristin:
Redox Heterogeneities Promote Thioarsenate Formation and Release into Groundwater from Low Arsenic Sediments.
In: Environmental Science & Technology. Vol. 54 (March 2020) Issue 6 . - pp. 3237-3244.
ISSN 0013-936X
DOI: https://doi.org/10.1021/acs.est.9b06502

Abstract in another language

Groundwater contamination by As from natural and anthropogenic sources is a world-wide concern. Redox heterogeneities over space and time are common and can influence the molecular-level speciation of As, and thus As release/retention, but are largely unexplored. Here we present results from a dual-domain column experiment, with natural organic-rich, fine-grained, and sulfidic sediments embedded as lenses (referred to as ‘reducing lenses’) within natural aquifer sand. We show that redox interfaces in sulfur-rich, alkaline aquifers may release concerning levels of As, even when sediment As concentration is low (<2 mg/kg), due to the formation of mobile thioarsenates at aqueous sulfide:Fe molar ratios <1. In our experiments, this behavior occurred in the aquifer sand between reducing lenses and was attributed to the spreading of sulfidic conditions and subsequent Fe reductive dissolution. In contrast, inside reducing lenses (and some locations in the aquifer) the aqueous sulfide:Fe molar ratios exceeded 1 and aqueous sulfide:As molar ratios exceeded 100, which partitioned As(III)-S to the solid phase (associated with organics or as realgar (As4S4)). These results highlight the importance of thioarsenates in natural sediments and indicate that redox interfaces and sediment heterogeneities could locally degrade groundwater quality, even in aquifers with unconcerning solid phase As concentrations.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Professor Environmental Geochemistry Group
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Professor Environmental Geochemistry Group > Professor Environmental Geochemistry - Univ.-Prof. Dr. Britta Planer-Friedrich
Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 500 Natural sciences
500 Science > 550 Earth sciences, geology
Date Deposited: 28 May 2020 07:08
Last Modified: 28 May 2020 07:08
URI: https://eref.uni-bayreuth.de/id/eprint/55295