Details
| Original language | English |
|---|---|
| Pages (from-to) | 7317-7326 |
| Number of pages | 10 |
| Journal | Environmental Science and Technology |
| Volume | 52 |
| Issue number | 13 |
| Publication status | Published - 31 May 2018 |
Abstract
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 zerovalent sulfur-containing species. Laboratory incubations with sulfide-reacted, purified model peat showed increasing total arsenic sorption with decreasing pH from 8.5 to 4.5 for both, monothioarsenate and arsenite. 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 toward 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.
ASJC Scopus subject areas
- Chemistry(all)
- Environmental Science(all)
- Environmental Chemistry
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In: Environmental Science and Technology, Vol. 52, No. 13, 31.05.2018, p. 7317-7326.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Monothioarsenate Transformation Kinetics Determining Arsenic Sequestration by Sulfhydryl Groups of Peat
AU - Besold, Johannes
AU - Biswas, Ashis
AU - Suess, Elke
AU - Scheinost, Andreas C.
AU - Rossberg, André
AU - Mikutta, Christian
AU - Kretzschmar, Ruben
AU - Gustafsson, Jon Petter
AU - Planer-Friedrich, Britta
N1 - Funding Information: This work was funded by the German Research Foundation Grant PL 302/20-1. A. Biswas received a Postdoc stipend from the Alexander-von-Humboldt Foundation. We acknowledge the help from R. Siegel and H. Zier for collecting the NMR and FT-IR spectra of the peat. Arsenic K-edge XAS xperiments were performed at the European Synchrotron Radiation Facility (ESRF), Grenoble, France, and the Stanford Synchrotron Radiation Lightsource (SSRL), a Directorate of SLAC National Accelerator Laboratory and an Office of Science User Facility operated for the US Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. In this regard, we would like to thank R. Davis (SSRL) and J. Lezama Pacheco (Soil and Environmental Biogeochemistry group, Stanford University) for their support in using beamline 4-1.
PY - 2018/5/31
Y1 - 2018/5/31
N2 - 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 zerovalent sulfur-containing species. Laboratory incubations with sulfide-reacted, purified model peat showed increasing total arsenic sorption with decreasing pH from 8.5 to 4.5 for both, monothioarsenate and arsenite. 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 toward 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.
AB - 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 zerovalent sulfur-containing species. Laboratory incubations with sulfide-reacted, purified model peat showed increasing total arsenic sorption with decreasing pH from 8.5 to 4.5 for both, monothioarsenate and arsenite. 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 toward 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.
UR - http://www.scopus.com/inward/record.url?scp=85048032248&partnerID=8YFLogxK
U2 - 10.1021/acs.est.8b01542
DO - 10.1021/acs.est.8b01542
M3 - Article
C2 - 29847919
AN - SCOPUS:85048032248
VL - 52
SP - 7317
EP - 7326
JO - Environmental Science and Technology
JF - Environmental Science and Technology
SN - 0013-936X
IS - 13
ER -