• 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.


Latest publications

Persistence of copper-based nanoparticle-containing foliar sprays in Lactuca sativa (lettuce) characterized by spICP-MS

Copper oxide and hydroxide nanoparticles (Cu-NPs) are components of some commercial pesticides. When these Cu-NPs dissolve in the environment, their size distribution, efficacy, and toxicity are altered. Since acute toxicity screens typically involve pristine NPs, quantification of the transformation of their size distribution in edible leaf vegetables is necessary for accurate consumer risk assessment. Single particle ICP-MS was used to investigate the persistence of three forms of Cu-NPs following foliar application to live lettuce (Lactuca sativa): CuO NP, Cu(OH)2 NP, and Kocide 3000®. A methanol-based digestion method was used to minimize Cu-NP dissolution during extraction from the leaf tissues. After dosing, the NPs associated with the leaf tissues were characterized over a 9-day period to monitor persistence. Nanoparticle counts and total copper mass concentrations remained constant, though the particle size distributions shifted down over time. Washing the leaves in tap water resulted in removal of total copper while the number of Cu-NPs remaining depended on the form applied. This work indicates that washing of lettuce preferentially removed dissolved Cu over Cu-NPs, and that the amount of residual Cu-NPs remaining is low when applied at the recommended rates for Kocide 3000®.

Stephanie Laughton, Adam Laycock, Frank von der Kammer, Thilo Hofmann, Elizabeth A. Casman, Sónia M. Rodrigues, Gregory V. Lowry
2019 - Journal of Nanoparticle Research, 174: in press

Groundwater Chemistry Has a Greater Influence on the Mobility of Nanoparticles Used for Remediation than the Chemical Heterogeneity of Aquifer Media

The application of nanoscale zerovalent iron (nano-ZVI) particles for groundwater remediation has spurred research into the influence of the collector heterogeneity on the nano-ZVI mobility. The chemical heterogeneity of surfaces within aquifer media affects their surface charge distribution and their affinity for nano-ZVI. The groundwater chemistry affects the properties of both aquifer surfaces and the nano-ZVI particles. Commercial poly(acrylic acid)-coated nano-ZVI (PAA–nano-ZVI) particles were tested in column experiments using two solution chemistries and silica collectors with different degrees of chemical heterogeneity, achieved by ferrihydrite coating. A porous media filtration model was used to determine the attachment efficiency of PAA–nano-ZVI particles, and the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory was used to describe the interactions between PAA–nano-ZVI particles and the aquifer “collectors”. The mobility of PAA–nano-ZVI particles suspended in ultrapure water depended on the extent of ferrihydrite coating on the collector surfaces. The mobility of PAA–nano-ZVI particles under environmentally relevant conditions was independent of the collector chemical heterogeneity. The size of PAA–nano-ZVI aggregates doubled, inducing gravitational sedimentation and possibly straining as mechanisms of particle deposition. There was no repulsive energy barrier between particles and collectors, and the DLVO theory was unable to explain the observed particle attachment. Our results suggest that the groundwater chemistry has a greater influence on the mobility of PAA–nano-ZVI particles than the collector chemical heterogeneity. A better understanding of polymer adsorption to nanoparticles and its conformation under natural groundwater conditions is needed to further elucidate nanoparticle–collector interactions.

Vesna Micić, Nathan Bossa, Doris Schmid, Mark R. Wiesner, Thilo Hofmann
2019 - Environmental Science & Technology, 1250-1257

The Carbon-Isotope Record of the Sub-Seafloor Biosphere

Sub-seafloor microbial environments exhibit large carbon-isotope fractionation effects as a result of microbial enzymatic reactions. Isotopically light, dissolved inorganic carbon (DIC) derived from organic carbon is commonly released into the interstitial water due to microbial dissimilatory processes prevailing in the sub-surface biosphere. Much stronger carbon-isotope fractionation occurs, however, during methanogenesis, whereby methane is depleted in 13C and, by mass balance, DIC is enriched in 13C, such that isotopic distributions are predominantly influenced by microbial metabolisms involving methane. Methane metabolisms are essentially mediated through a single enzymatic pathway in both Archaea and Bacteria, the Wood–Ljungdahl (WL) pathway, but it remains unclear where in the pathway carbon-isotope fractionation occurs. While it is generally assumed that fractionation arises from kinetic effects of enzymatic reactions, it has recently been suggested that partial carbon-isotope equilibration occurs within the pathway of anaerobic methane oxidation. Equilibrium fractionation might also occur during methanogenesis, as the isotopic difference between DIC and methane is commonly on the order of 75‰, which is near the thermodynamic equilibrium. The isotopic signature in DIC and methane highly varies in marine porewaters, reflecting the distribution of different microbial metabolisms contributing to DIC. If carbon isotopes are preserved in diagenetic carbonates, they may provide a powerful biosignature for the conditions in the deep biosphere, specifically in proximity to the sulphate–methane transition zone. Large variations in isotopic signatures in diagenetic archives have been found that document dramatic changes in sub-seafloor biosphere activity over geological time scales. We present a brief overview on carbon isotopes, including microbial fractionation mechanisms, transport effects, preservation in diagenetic carbonate archives, and their implications for the past sub-seafloor biosphere and its role in the global carbon cycle. We discuss open questions and future potentials of carbon isotopes as archives to trace the deep biosphere through time.

Patrick Meister, Carolina Reyes
2019 - Geosciences, 9: in press

Lecture series

ESR as a tool to investigate environmentally persistent and short-lived radicals

Prof. Dr Marc Pignitter
Department of Physiological Chemistry, University of Vienna, Austria
16:30 h
Eberhard Clar-Saal (2B 204), Althanstrasse 14 UZA II, 1090 Vienna