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Monothioarsenate transformation kinetics determining arsenic sequestration by sulfhydryl groups of peat

Title data

Besold, Johannes ; Biswas, Ashis ; Suess, Elke ; Scheinost, Andreas C. ; Rossberg, André ; Mikutta, Christian ; Kretzschmar, Ruben ; Gustafsson, Jon P. ; Planer-Friedrich, Britta:
Monothioarsenate transformation kinetics determining arsenic sequestration by sulfhydryl groups of peat.
In: Environmental Science & Technology. Vol. 52 (2018) Issue 13 . - pp. 7317-7326.
ISSN 0013-936X
DOI: https://doi.org/10.1021/acs.est.8b01542

Abstract in another language

In peatlands, arsenite was reported to be effectively sequestered by sulfhydryl groups of natural organic matter. To which extent porewater arsenite can react with reduced sulfur to form thioarsenates and how this affects arsenic sequestration in peatlands, is unknown. Here, we show that in the naturally arsenic-enriched peatland Gola di Lago, Switzerland, up to 93% of all arsenic species in surface and porewaters were thioarsenates. The dominant species, monothioarsenate, likely formed from arsenite and zero-valent sulfur-containing species. Laboratory incubations with sulfide-reacted, purified model peat showed for both, monothioarsenate and arsenite, increasing total arsenic sorption with decreasing pH from 8.5 to 4.5. However, X-ray absorption spectroscopy revealed no binding of monothioarsenate via sulfhydryl groups. The sorption observed at pH 4.5 was acid-catalyzed dissociation of monothioarsenate, forming arsenite. The lower the pH and the more sulfhydryl sites, the more arsenite sorbed which in turn shifted equilibrium towards further dissociation of monothioarsenate. At pH 8.5, monothioarsenate was stable over 41 days. In conclusion, arsenic can be effectively sequestered by sulfhydryl groups in anoxic, slightly acidic environments where arsenite is the only arsenic species. At neutral to slightly alkaline pH, monothioarsenate can form and its slow transformation into arsenite and low affinity to sulfhydryl groups suggest that this species is mobile in such environments.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER146419
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Professorship Environmental Geochemistry Group
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Professorship Environmental Geochemistry Group > Professorship Environmental Geochemistry - Univ.-Prof. Dr. Britta Planer-Friedrich
Research Institutions
Research Institutions > Research Centres
Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Result of work at the UBT: Yes
DDC Subjects: 500 Science
Date Deposited: 29 Mar 2019 08:59
Last Modified: 29 Mar 2019 08:59
URI: https://eref.uni-bayreuth.de/id/eprint/48143