• Centre for Microbiology and Environmental Systems Science

  • CUBE - Computational Systems Biology

  • DOME - Microbial Ecology

  • EDGE - Environmental Geosciences

  • TER - Terrestrial Ecosystem Research


Latest publications

Redox Heterogeneities Promote Thioarsenate Formation and Release into Groundwater from Low Arsenic Sediments

Groundwater contamination by As from natural and anthropogenic sources is a worldwide concern. Redox heterogeneities over space and time are common and can influence the molecular-level speciation of As, and thus, As release/retention but are largely unexplored. Here, we present results from a dual-domain column experiment, with natural organic-rich, fine-grained, and sulfidic sediments embedded as lenses (referred to as “reducing lenses”) within natural aquifer sand. We show that redox interfaces in sulfur-rich, alkaline aquifers may release concerning levels of As, even when sediment As concentration is low (<2 mg/kg), due to the formation of mobile thioarsenates at aqueous sulfide/Fe molar ratios <1. In our experiments, this behavior occurred in the aquifer sand between reducing lenses and was attributed to the spreading of sulfidic conditions and subsequent Fe reductive dissolution. In contrast, inside reducing lenses (and some locations in the aquifer) the aqueous sulfide/Fe molar ratios exceeded 1 and aqueous sulfide/As molar ratios exceeded 100, which partitioned As(III)–S to the solid phase (associated with organics or as realgar (As4S4)). These results highlight the importance of thioarsenates in natural sediments and indicate that redox interfaces and sediment heterogeneities could locally degrade groundwater quality, even in aquifers with unconcerning solid-phase As concentrations.

Naresh Kumar, Vincent Noël, Britta Planer-Friedrich, Johannes BesoldJ, uan Lezama-Pacheco, John R. Bargar, Gordon E. Brown Jr., Scott Fendorf, Kristin Boye
2020 - Environmental Science & Technology, in press

Accurate quantification of TiO2 nanoparticles in commercial sunscreens using standard materials and orthogonal particle sizing methods for verification

The implementation and enforcement of product labeling obligation as required, for example, by the cosmetic product regulation, needs simple and precise validated analytical methods. This also applies to the analysis of nanoparticles in products such as cosmetics. However, the provision of such methods is often hampered by inaccurate sizing due to unwanted nanoparticle changes, interference of matrix components with sizing and interactions between nanoparticles and analytical instrumentation. It is, therefore, necessary to develop appropriate sample preparation methods that preserve NP properties and reduce or remove matrix compounds that interfere with sizing. Further, accurate particle size analysis of samples containing unknown and possibly multiple nanoparticulate constituents is needed. In this study, we evaluated three sample preparation methods to identify and quantify TiO2 nanoparticles in sunscreens. Specifically, we used a combination of ultracentrifugation and hexane washing, thermal destruction of the matrix, and surfactant assisted particle extraction. The method accuracy was assessed by two internal reference samples: pristine TiO2 nanoparticles (NM104) and similar TiO2 nanoparticles dispersed in a sunscreen matrix. The PSDs were determined using an asymmetrical flow field-flow fractionation hyphenated with multi-angle light scattering and inductively coupled plasma-mass spectroscopy. Particle sizing was based on size calibration of the particle retention time in the AF4. Computation of radius of gyration from MALS data was used as an orthogonal particle sizing approach to verify ideal elution and particle size data from the AF4 calibration. Among the three tested sample preparation methods surfactant assisted particle extraction revealed TiO2 nanoparticle recoveries of above 90% and no increase in particle size due to sample preparation was observed. Finally, the sample preparation methods were applied to two commercial sunscreen samples revealing the existence of TiO2-NP < 100 nm. Conclusively, the surfactant assisted particle extraction method can provide valid data for TiO2-NPs in sunscreen and possibly for cosmetic samples of similar matrix.

Milica Velimirovic, Stephan Wagner, Fazel Abdolahpur Monikh, Toni Uusimäki, Ralf Kaegi, Thilo Hofmann, Frank von der Kammer
2020 - Talanta, 215: in press

The ecology of heterogeneity: soil bacterial communities and C dynamics

Heterogeneity is a fundamental property of soil that is often overlooked in microbial ecology. Although it is generally accepted that the heterogeneity of soil underpins the emergence and maintenance of microbial diversity, the profound and far-reaching consequences that heterogeneity can have on many aspects of microbial ecology and activity have yet to be fully apprehended and have not been fully integrated into our understanding of microbial functioning. In this contribution we first discuss how the heterogeneity of the soil microbial environment, and the consequent uncertainty associated with acquiring resources, may have affected how microbial metabolism, motility and interactions evolved and, ultimately, the overall microbial activity that is represented in ecosystem models, such as heterotrophic decomposition or respiration. We then present an analysis of predicted metabolic pathways for soil bacteria, obtained from the MetaCyc pathway/genome database collection ( The analysis suggests that while there is a relationship between phylogenic affiliation and the catabolic range of soil bacterial taxa, there does not appear to be a trade-off between the 16S rRNA gene copy number, taken as a proxy of potential growth rate, of bacterial strains and the range of substrates that can be used. Finally, we present a simple, spatially explicit model that can be used to understand how the interactions between decomposers and environmental heterogeneity affect the bacterial decomposition of organic matter, suggesting that environmental heterogeneity might have important consequences on the variability of this process.

Nunan N, Schmidt H, Raynaud X
2020 - Phil. Trans. R. Soc. B, 1798: 11

Lecture series

New insights into the fate of silver nanoparticles in natural waters

Prof. Dr. Subhasis Goshal
Department of Civil Engineering, McGill University, Canada
16:30 h
Eberhard Clar-Saal (2B 204), Althanstrasse 14 UZA II, 1090 Vienna

Ancient DNA from Speleothems: A New Archive for Paleogenetic Research

Dr. Mareike Stahlschmidt
Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Germany
16:30 h
Eberhard Clar-Saal (2B 204), Althanstrasse 14 UZA II, 1090 Vienna

Organic Contaminants in Reclaimed Wastewater – Environmental Fate and Accumulation in Crop Plants

Prof. Dr. Joel Pedersen
Department of Soil Sciences, University of Wisconsin-Madison, USA
16:30 h
Eberhard Clar-Saal (2B 204), Althanstrasse 14 UZA II, 1090 Vienna