Hydrogeochemische Speziierung von Arsen, Gold und Kupfer in Eisen-Sulfid-Systemen unter Berücksichtigung abiotischer und mikrobiell katalysierter Wechselwirkungen
Zusammenfassung der Projektergebnisse
Arsenic-sulfur compounds, so-called thioarsenates (AsVO4-xSx3-), were the focus of the present project. Even though the affinity between arsenic and sulfur has been known for a long time, the relevance of thioarsenic species in environmental chemistry is only slowly emerging. A subproject dealt with other elements (antimony, molybdenum, and tungsten) which we found to form thiolated species in the environment as well. Key achievements within the present project were to: • reconcile contradictory spectroscopic and chromatographic evidence that has existed for arsenic-sulfur species for about 10 years by showing that besides oxygen also total concentration, more exactly S:As and SH-:OH-ratios, determine which species is measured; provide unambiguous XAS spectra for thioarsenates and thioarsenites, and an indirect chromatographic method for thioarsenite determination; • introduce a model for thioarsenite/thioarsenate formation showing that thioarsenites form from arsenite via ligand exchange when SH- > OH- and are necessary precursors for thioarsenates which form by addition of elemental sulfur to the trivalent species; • detect that thioarsenates form spontaneously during dissimilatory arsenate reduction with sulfide as electron donor and can be used by thermophilic and halophilic chemolithotrophs either during aerobic growth or anoxygenic photosynthesis; • develop and validate different stabilization methods (EDTA, ethanol, solid phase extraction) for sample preservation of thioarsenates in the presence of iron; • prove that thioarsenates can form and prevail in iron-rich systems despite reaction of free sulfide with iron to form iron sulfide phases and show that sulfate reduction increases arsenite desorption from iron (hydr)oxides by in-situ formation of thioarsenates which show less sorption to almost all iron minerals than arsenite and arsenate; • show that thioarsenates pass the human gastrointestinal barrier intact, that their acute toxicity to bladder, liver, and skin cells is lower than that of arsenite but higher than that of arsenate and that toxicity increases with an increasing degree of thiolation; • show for the model plant Arabidopsis thaliana that monothioarsenate uptake in plants is less than that of arsenate, that is also induces phytochelatin formation as detoxification mechanism in plants and has a lower toxicity than arsenite but a higher toxicity than arsenate; • confirm that thioarsenates occur ubiquitously in sulfate-reducing systems ranging from geothermal waters, mofettes, submarine degassing fumaroles and hot springs, stagnant saline lakes, groundwaters, and - especially important for future research on uptake, toxicity, and tolerance of arsenic in rice - in paddy soils; • deliver first proof of the existence of thioantimonates in natural waters, determine their stability and competing interactions with arsenic; • develop a method for determination of thiomolybdates in natural waters by ion pair chromatography-ICP-MS and provide the grounds for re-evaluation of the use of Mo as palaeproxy by showing that isotope fractionation occurs during thiolation and confounds interpretation of sediment records in sulfidic environments which are not in full equilibrium.
Projektbezogene Publikationen (Auswahl)
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A critical investigation of hydride generation-based arsenic speciation in sulfidic waters. Environmental Science & Technology, 43, 5007-5013 (2009)
Planer-Friedrich B, Wallschläger D
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Arsenic speciation in sulfidic waters: Reconciling contradictory spectroscopic and chromatographic evidence. Analytical Chemistry 82, 10228-10235 (2010)
Planer-Friedrich B, Suess E, Scheinost AC, Wallschlaeger D
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Formation and structural characterization of tri- and tetrathioantimonate and their natural occurrence in geothermal waters. Environmental Science & Technology, 45, 6855–6863 (2011)
Planer-Friedrich B & Scheinost AC
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Thioarsenate transformation by filamentous microbial mats thriving in an alkaline, sulfidic hot spring. Environmental Science & Technology, 46(8), 4348–4356 (2012)
Haertig C & Planer-Friedrich B
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Coupling of arsenic mobility to sulfur transformations during microbial sulfate reduction in the presence and absence of humic acid. Chemical Geology, 343, 12-24 (2013)
Burton E, Johnston S, Planer-Friedrich B
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Chemolithotrophic Growth of the Aerobic Hyperthermophilic Bacterium Thermocrinis ruber OC 14/7/2 on Monothioarsenate and Arsenite, FEMS Microbiology Ecology, 90, 747–760 (2014)
Haertig C, Lohmayer R, Kolb S, Horn MA, Inskeep WP, Planer-Friedrich B
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Anaerobic Chemolithotrophic Growth of the Haloalkaliphilic Bacterium Strain MLMS-1 by Disproportionation of Monothioarsenate, Environmental Science & Technology, 49(11), 6554–6563 (2015)
Planer-Friedrich B, Haertig C, Lohmayer R, Suess E, McCann S, Oremland R
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Anoxic, ethanolic, and cool – an improved method for thioarsenate preservation in iron-rich waters, Applied Geochemistry, 62, 224–233 (2015)
Suess E, Mehlhorn J, Planer-Friedrich B
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Inorganic and methylated thioarsenates pass the gastrointestinal barrier, Chemical Research in Toxicology, 28(9), 1678–1680 (2015)
Hinrichsen S, Geist F, Planer-Friedrich B
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Ion pair chromatography coupled to ICP-MS as a method for thiomolybdate speciation in natural waters, Analytical Chemistry, 87(6), 3388-3395 (2015)
Lohmayer R, Reithmaier G, Bura-Nakic E, Planer-Friedrich B
