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Stabilization of thioarsenates in iron-rich waters

Title data

Süß, Elke ; Wallschläger, Dirk ; Planer-Friedrich, Britta:
Stabilization of thioarsenates in iron-rich waters.
In: Chemosphere. Vol. 83 (2011) Issue 11 . - pp. 1524-1531.
ISSN 1879-1298
DOI: https://doi.org/10.1016/j.chemosphere.2011.01.045

Abstract in another language

In recent years, thioarsenates have been shown to be important arsenic species in sulfidic, low-iron waters. Here, we show for the first time that thioarsenates also occur in iron-rich ground waters, and that all methods previously used to preserve arsenic speciation (acidification, flash-freezing, or EDTA addition) fail to preserve thioarsenates in such matrices. Laboratory studies were conducted to identify the best approach for stabilizing thioarsenates by combination and modification of the previously-applied methods. Since acidification was shown to induce conversions between thioarsenates and precipitation of arsenic-sulfide minerals, we first conducted a detailed study of thioarsenate preservation by flash-freezing. In pure water, thioarsenates were stable for 21 days when the samples were flash-frozen and cryo-stored with a minimal and anoxic headspace. Increasing headspace volume and oxygen presence in the headspace were detrimental to thioarsenate stability during cryo-storage. Addition of NaOH (0.1 mol/L) or EtOH (1% V/V) counteracted these effects and stabilized thioarsenates during cryo-storage. Addition of Fe(II) to thioarsenate solutions caused immediate changes in arsenic speciation and a loss of total arsenic from solution during cryo-storage. Both effects were largely eliminated by addition of a neutral EDTA solution, and thioarsenates were significantly stabilized during cryo-storage by this procedure. Neutralization of EDTA was required to prevent alteration of thioarsenate speciation through pH change. With the modified method (anoxic cryo-preservation by flash-freezing with minimal headspace after addition of neutralized EDTA-solution), the fractions of mono- and dithioarsenate, the two thioarsenates observed in the iron-rich ground waters, remained stable over a cryo-storage period of 11 days. Further modifications are needed for the higher SH-substituted thioarsenates (tri- and tetrathioarsenate), which were not encountered in the studied iron-rich ground waters.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER92225
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 Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences
Research Institutions
Research Institutions > Research Centres
Result of work at the UBT: Yes
DDC Subjects: 500 Science
Date Deposited: 05 May 2015 12:10
Last Modified: 10 Jan 2018 09:14
URI: https://eref.uni-bayreuth.de/id/eprint/12787