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Seasonal Formation of Low-Sorbing Methylthiolated Arsenates Induces Arsenic Mobilization in a Minerotrophic Peatland

Title data

Knobloch, Philipp Victor Thorben ; Pham, Lan Huong ; Kerl, Carolin ; Guo, Qinghai ; Planer-Friedrich, Britta:
Seasonal Formation of Low-Sorbing Methylthiolated Arsenates Induces Arsenic Mobilization in a Minerotrophic Peatland.
In: Environmental Science & Technology. Vol. 58 (2024) Issue 3 . - pp. 1669-1679.
ISSN 0013-936X
DOI: https://doi.org/10.1021/acs.est.3c05771

Abstract in another language

Peatlands are known sinks for arsenic (As). In the present study, seasonal As mobilization was observed in an acidic, minerotrophic peatland (called Lehstenbach) in late summer, accompanied by a peak in dissolved sulfide (S(-II)). Arsenic speciation revealed the lowest seasonal porewater concentrations of arsenite and arsenate, likely due to As(III)-S-bridging to natural organic matter. Arsenic mobilization was driven by the formation of arsenite-S(-II) colloids and formation of methylthiolated arsenates (up to 59% of the sum of As species) and to a minor extent also of inorganic thioarsenates (6%–30%) and oxymethylated arsenates (5%–24%). Sorption experiments using a purified model peat, the Lehstenbach peat, natural (to mimic winter conditions) and reacted with S(-II) (to mimic late summer conditions) at acidic and neutral pH confirmed low sorption of methylthiolated arsenates. At acidic pH and in the presence of S(-II), oxymethylated arsenates were completely thiolated. This methylthiolation decreased As sorption up to 10 and 20 times compared with oxymethylated arsenates and arsenite, respectively. At neutral pH, thiolation of monomethylated arsenates was incomplete, and As could be partially retained as oxymethylated arsenates. Dimethylated arsenate was still fully thiolated and highly mobile. Misidentification of methylthiolated arsenates as oxymethylated arsenates might explain previous contradictory reports of methylation decreasing or increasing As mobility.

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 > Professor Environmental Geochemistry - Univ.-Prof. Dr. Britta Planer-Friedrich
Research Institutions > Central research institutes > Bayreuth Center of Ecology and Environmental Research- BayCEER
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 550 Earth sciences, geology
Date Deposited: 25 Jan 2024 08:39
Last Modified: 25 Jan 2024 08:39
URI: https://eref.uni-bayreuth.de/id/eprint/88334