• We investigate pollutants and nutrients in the environment.

  • We elucidate processes and mechanisms in the field and laboratory.

  • Nanogeosciences: exploring the nanoscale to understand processes of global relevance.

  • We use models to quantify processes and mechanisms.

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Latest publications

Identifying the reactive sites of hydrogen peroxide decomposition and hydroxyl radical formation on chrysotile asbestos surfaces

Chrysotile asbestos is a carcinogenic mineral that has been abundantly used in different industrial and consumer applications. The fibers’ toxicity is partly goverend by the formation of highly reative radicals by active surface sites.

Stephan Kraemer from EDGE together with the former PhD student Martin Walter and university assistant Walter Schenkeveld investigated these reactive sites on chrysotile asbestos surfaces, in cooperation with the collegues Lars Gille and Gerald Geroldinger from VetMed Vienna and Michael Reissner from TU Vienna.

The authors identified tetrahedrally coordinated Fe on the surface of chrysotile asbestos as the only relevant site in the formation of the highly reactive and toxic hydroxyl radicals, which readily damage DNA, proteins and lipids and hence contribute to the pathogenicity of the fibers. Fe added to chrysotile fibers increased the formation of hydroxyl radicals only when it became incorporated and coordinated into tetrahedral vacancy sites on asbestos surfaces.

Martin Walter, Walter D. C. Schenkeveld, Gerald Geroldinger, Lars Gille, Michael Reissner & Stephan M. Kraemer
2020 - Particle and Fibre Toxicology, 17: 3

Copper limiting threshold in the terrestrial ammonia oxidizing archaeon Nitrososphaera viennensis

Ammonia oxidizing archaea (AOA) inhabiting soils have a central role in the global nitrogen cycle. Copper (Cu) is central to many enzymes in AOA including ammonia monooxygenase (AMO), the enzyme involved in the first step of ammonia oxidation. This study explored the physiological response of the AOA soil isolate, Nitrososphaera viennensis (EN76T) to Cu-limiting conditions in order to approach its limiting threshold under laboratory conditions. The chelator TETA (1,4,8,11-tetraazacyclotetradecane N, N′, N″, N‴-tetraacetic acid hydrochloride hydrate) with selective affinity for Cu2+ was used to lower bioavailable Cu2+ in culture experiments as predicted by thermodynamic speciation calculations. Results show that N. viennensis is Cu-limited at concentrations ≤10−15 mol L−1 free Cu2+ compared to standard conditions (10−12 mol L−1). This Cu2+ limiting threshold is similar to pure cultures of denitrifying bacteria and other AOA and AOB inhabiting soils, freshwaters and sewage (<10−16 mol L−1), and lower than pure cultures of the marine AOA Nitrosopumilus maritimus (<10−12.7 mol L−1), which also possesses a high amount of Cu-dependent enzymes.

Carolina Reyes, Logan H.Hodgskiss, Oliver Baars, Melina Kerou, Barbara Bayer, Christa Schleper, Stephan M.Kraemer
2020 - Research in microbiology, in press

Enhanced chromium(VI) treatment in electroactive constructed wetlands: Influence of conductive material

A constructed wetland (CW) microcosm based on conductive graphite gravel was investigated for hexavalent chromium (Cr(VI)) treatment from synthetic wastewater. Its performance was evaluated and compared with a traditional gravel-based CW microcosm. The microcosms were operated at varying initial Cr(VI) concentrations (5−20 mg/L) and hydraulic retention times (HRT) (3–7.5 h). Near complete treatment (99.9 ± 0.06 %) was achieved in the graphite-based microcosm throughout the experiment. The performance was consistently high throughout with 42.9 % improvement in Cr (VI) treatment compared to a traditional gravel microcosm. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) analysis indicated that chromium was adsorbed to microbial biofilms. Moreover, microbial diversity profiling suggested that the microbial population in both microcosms differed in diversity and communities. The results suggest that the use of conductive materials in CW significantly enhances the treatment of Cr(VI) and more importantly, allows microbial activity even at high levels of Cr(VI) in the CW.

Pratiksha Srivastava, Rouzbeh Abbassi, Asheesh Kumar Yadav, Vikram Garaniya, Naresh Kumar, Stuart J.Khan, Trevor Lewis
2020 - Journal of Hazardous Materials, 387: 121722