PhD Thesis

Microbially catalyzed reactions of arsenic and sulfur in extreme environments

Cornelia Härtig (04/2009-01/2017)

Support: Britta Planer-Friedrich

Emmy Noether DFG Stelle (Promotion nicht beendet)

The inorganic arsenic chemistry in suboxic aquatic systems is not only characterized by the arsenic-oxide species arsenite and arsenate.  Moreover arsenic-sulfur species may form, the so-called thioarsenates, as resent research activities by Prof. B. Planer-Friedrich revealed. Especially in alkaline sulfidic springs in the Yellowstone National Park high proportions of thioarsenates were detected, constituting up to 80 % of total arsenic in the spring waters. Four distinct thioarsenate species are known (mono-, di, tri- and tetrathioarsenate) and highest concentrations were detectable at the source of different Yellowstone hot springs. Samplings along drainage channels revealed that pentavalent thioarsenates were transformed successively over trivalent arsenite to pentavalent arsenate. Transformation rates in nature are much faster than in abiotic laboratory experiments, pointing out that microbes may accelerate these processes.

The purpose of the PhD is to investigate the role of microbially catalyzed versus abiotic thioarsenate transformations in the laboratory and under natural conditions. The field investigations will start in Summer 2009. The hydrochemistry and contemporary the microbial communities occurring at different points in the drainage channels at several alkaline, sulfidic thermal springs in Yellowstone National Park will be characterized. Further Investigations will include thermal features in the Taupo Volcanic Centre, New Zealand.