• We investigate the dynamics of 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

NO2 and natural organic matter affect both soot aggregation behavior and sorption of S-metolachlor

Soot is an important carbonaceous nanoparticle (CNP) frequently found in natural environments. Its entry into surface waters can occur directly via surface runoff or infiltration, as well as via atmospheric deposition. Pristine soot is likely to rapidly undergo aggregation and subsequent sedimentation in aquatic environments. Further, soot can sorb a variety of organic contaminants, such as S-metolachlor (log KD = 3.25 ± 0.12). During atmospheric transport, soot can be chemically transformed by reactive oxygen species including NO2. The presence of natural organic matter (NOM) in surface waters can further affect the aquatic fate of soot. To better understand the processes driving the fate of soot and its interactions with contaminants, pristine and NO2-transformed model soot suspensions were investigated in the presence and absence of NOM. NO2-oxidized soot showed a smaller particle size, a higher number of particles remaining in suspension, and a decreased sorption of S-metolachlor (log KD = 2.47 ± 0.40). In agreement with findings for other CNPs, soot stability against aggregation was increased for both pristine and NO2 transformed soot in the presence of NOM.

Gabriel Sigmund, Stephanie Castan, Christopher Wabnitz, Rani Bakkour, Thorsten Hüffer, Thilo Hofmann, Martin Elsner
2019 - Environmental Science: Processes & Impacts, in press

Chemosymbiotic bivalves contribute to the nitrogen budget of seagrass ecosystems

In many seagrass sediments, lucinid bivalves and their sulfur-oxidizing symbionts are thought to underpin key ecosystem functions, but little is known about their role in nutrient cycles, particularly nitrogen. We used natural stable isotopes, elemental analyses, and stable isotope probing to study the ecological stoichiometry of a lucinid symbiosis in spring and fall. Chemoautotrophy appeared to dominate in fall, when chemoautotrophic carbon fixation rates were up to one order of magnitude higher as compared with the spring, suggesting a flexible nutritional mutualism. In fall, an isotope pool dilution experiment revealed carbon limitation of the symbiosis and ammonium excretion rates up to tenfold higher compared with fluxes reported for nonsymbiotic marine bivalves. These results provide evidence that lucinid bivalves can contribute substantial amounts of ammonium to the ecosystem. Given the preference of seagrasses for this nitrogen source, lucinid bivalves’ contribution may boost productivity of these important blue carbon ecosystems.
Ulisse Cardini, Marco Bartoli, Sebastian Lücker, Maria Mooshammer, Julia Polzin, Raymond W. Lee, Vesna Micić, Thilo Hofmann, Miriam Weber, Jillian M. Petersen
2019 - The ISME journal, in press

Mercury Isotope Fractionation in the Subsurface of a Hg(II) Chloride-Contaminated Industrial Legacy Site

To understand the transformations of mercury (Hg) species in the subsurface of a HgCl2-contaminated former industrial site in southwest Germany, Hg isotope analysis was combined with an investigation of Hg forms by a four-step sequential extraction protocol (SEP) and pyrolytic thermodesorption. Data from two soil cores revealed that the initial HgCl2was partly reduced to metallic Hg(0) and that Hg forms of different mobility and oxidation state coexist in the subsurface. The most contaminated sample (K2-8, 802 mg kg–1 Hg) had a bulk δ202Hg value of around −0.43 ± 0.06‰ (2SD), similar to published average values for industrial Hg sources. Other sample signatures varied significantly with depth and between SEP pools. The most Hg-rich samples contained mixtures of Hg(0) and Hg(II) phases, and the water-extractable, mobile Hg pool exhibited heavy δ202Hg values of up to +0.18‰. Sequential water extracts revealed slow dissolution kinetics of mobile Hg pools, continuously releasing isotopically heavy Hg into solution. This was further corroborated by heavy δ202Hg values of groundwater samples. Our results demonstrate that the Hg isotope signature of an industrial contamination source can be significantly altered during the transformations of Hg species in the subsurface, which complicates source tracing applications but offers the possibility of using Hg isotopes as process tracers in contaminated subsurface systems.

Flora M. Brocza, Harald Biester, Jan-Helge Richard, Stephan M. Kraemer, Jan G. Wiederhold
2019 - Environmental Science & Technology, 13: 7296-7305

Lecture series

Computational modeling and learning methods for metagenomics of microbial and viral communities

Prof. Dr Thomas Rattei
Department of Microbiology and Ecosystem Science, University of Vienna, Austria
21.10.2019
16:30 h
Eberhard Clar-Saal (2B 204), Althanstrasse 14 UZA II, 1090 Vienna

Global wildfires - trends, impacts and their role in the carbon cycle

Dr Cristina Santin, Prof. Dr Stefan Doerr
Department of Geography, Swansea University, UK
11.11.2019
16:30 h
Eberhard Clar-Saal (2B 204), Althanstrasse 14 UZA II, 1090 Vienna

Carbon cycling in groundwater ecosystems – what do we know and where are the knowledge gaps?

Prof. Dr Christian Griebler
Department of Limnology and Bio-Oceanography, University of Vienna, Austria
18.11.2019
16:30 h
Eberhard Clar-Saal (2B 204), Althanstrasse 14 UZA II, 1090 Vienna