Publications

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Publications in peer reviewed journals

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

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

    Abstract: 

    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.

  • Copper limiting threshold in the terrestrial ammonia oxidizing archaeon Nitrososphaera viennensis

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

    Abstract: 

    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.

  • Deep Learning Neural Network Approach for Predicting the Sorption of Ionizable and Polar Organic Pollutants to a Wide Range of Carbonaceous Materials

    Gabriel Sigmund, Mehdi Gharasoo, Thorsten Hüffer, Thilo Hofmann
    2020 - Environmental Science & Technology, 54: 4583-4591

    Abstract: 

    Most contaminants of emerging concern are polar and/or ionizable organic compounds, whose removal from engineered and environmental systems is difficult. Carbonaceous sorbents include activated carbon, biochar, fullerenes, and carbon nanotubes, with applications such as drinking water filtration, wastewater treatment, and contaminant remediation. Tools for predicting sorption of many emerging contaminants to these sorbents are lacking because existing models were developed for neutral compounds. A method to select the appropriate sorbent for a given contaminant based on the ability to predict sorption is required by researchers and practitioners alike. Here, we present a widely applicable deep learning neural network approach that excellently predicted the conventionally used Freundlich isotherm fitting parameters log KF and n (R2 > 0.98 for log KF, and R2 > 0.91 for n). The neural network models are based on parameters generally available for carbonaceous sorbents and/or parameters freely available from online databases. A freely accessible graphical user interface is provided.

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

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

    Abstract: 

    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.

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

    Vesna Micić, Nathan Bossa, Doris Schmid, Mark R. Wiesner, Thilo Hofmann
    2020 - Environmental Science & Technology, 54: 1250-1257

    Abstract: 

    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.

  • Harmonizing across environmental nanomaterial testing media for increased comparability of nanomaterial datasets

    Nicholas K. Geitner, Christine Ogilvie Hendren, Geert Cornelis, Ralf Kaegi, Jamie R. Lead, Gregory V. Lowry, Iseult Lynch, Bernd Nowack, Elijah Petersen, Emily Bernhardt, Scott Brown, Wei Chen, Camille de Garidel-Thoron, Jaydee Hanson, Stacey Harper, Kim Jones, Frank von der Kammer, Alan Kennedy, Justin Kidd, Cole Matson, Chris D. Metcalfe, Joel Pedersen, Willie J. G. M. Peijnenburg, Joris T. K. Quik, Sónia M. Rodrigues, Jerome Rose, Phil Sayre, Marie Simonin, Claus Svendsen, Robert Tanguay, Nathalie Tefenkji, Tom van Teunenbroek, Gregory Thies, Yuan Tian, Jacelyn Rice, Amalia Turner, Jie Liu, Jason Unrine, Marina Vance, Jason C. White, Mark R. Wiesner
    2020 - Environmental Science: Nano, 7: 13-36

    Abstract: 

    The chemical composition and properties of environmental media determine nanomaterial (NM) transport, fate, biouptake, and organism response. To compare and interpret experimental data, it is essential that sufficient context be provided for describing the physical and chemical characteristics of the setting in which a nanomaterial may be present. While the nanomaterial environmental, health and safety (NanoEHS) field has begun harmonization to allow data comparison and re-use (e.g. using standardized materials, defining a minimum set of required material characterizations), there is limited guidance for standardizing test media. Since most of the NM properties driving environmental behaviour and toxicity are medium-dependent, harmonization of media is critical. A workshop in March 2016 at Duke University identified five categories of test media: aquatic testing media, soil and sediment testing media, biological testing media, engineered systems testing media and product matrix testing media. For each category of test media, a minimum set of medium characteristics to report in all NM tests is recommended. Definitions and detail level of the recommendations for specific standardized media vary across these media categories. This reflects the variation in the maturity of their use as a test medium and associated measurement techniques, variation in utility and relevance of standardizing medium properties, ability to simplify standardizing reporting requirements, and in the availability of established standard reference media. Adoption of these media harmonization recommendations will facilitate the generation of integrated comparable datasets on NM fate and effects. This will in turn allow testing of the predictive utility of functional assay measurements on NMs in relevant media, support investigation of first principles approaches to understand behavioral mechanisms, and support categorization strategies to guide research, commercial development, and policy.

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

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

    Abstract: 

    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.

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

    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

    Abstract: 

    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.

  • Remediation of fluoride contaminated water using encapsulated active growing blue-green algae, Phormidium sp.

    Yamini Mittal, Pratiksha Srivastav, Naresh Kumar, Asheesh KumarYadav
    2020 - Environmental Technology and Innovation, in press

    Abstract: 

    Elevated fluoride concentration in drinking water is a global concern that impacts health of millions. Developing low cost remediation methods empower communities with fewer resources available to protect their health.

    Together with colleagues from CSIR India, and University of Tasmania in Australia, we have demonstrated that fluoride can be removed by using common blue-green algae, Phormidium sp. Using Response Surface Methodology (RSM) we were able to optimize parameters for the highest fluoride removal in our system. Further work is currently ongoing on process optimization to develop a household level pilot scale experimental reactor in a small village in eastern India.

  • The removal of lead, copper, zinc and cadmium from aqueous solution by biochar and amended biochars

    Stuart Cairns, Ian Robertson, Gabriel Sigmund, Alayne Street-Perrott
    2020 - Environmental Science and Pollution Research, in press

    Abstract: 

    The exponential growth in the use of motor vehicles is a key contributor to freshwater degradation. Current remediation techniques require prohibitively expensive contaminant treatment and extraction. Biochar represents an inexpensive option to ameliorate contaminants from motorway runoff. Biochar from Norway spruce (Picea abies (L.) Karst.) was produced under fast pyrolysis-gasification (450–500 °C for 90 s) and amended with wood ash and basaltic rock dust to evaluate sorption of Pb, Cu, Zn and Cd. The column study, designed to mimic field conditions, confirmed that unamended biochar can bind contaminants for short periods, but that the addition of amendments, particularly wood ash, significantly improves contaminant removal. Wood ash-amended biochar removed 98–100% of all contaminants during the study, driven by pH (r = 0.73–0.74; p < 0.01 dependent on metal species) and phosphorus levels causing precipitation (r = 0.47–0.59; p < 0.01, dependent on metal species). The contaminants’ progression through the biochar subsections in the column indicated that increasing the thickness of the biochar layer increased contaminant residence time and removal.

  • Wood-based activated biochar to eliminate organic micropollutants from biologically treated wastewater

    Nikolas Hagemann, Hans-Peter Schmidt, Ralf Kaegi, Mark Boehler, Gabriel Sigmund, Andreas Maccagnan, Christa S. McArdell, Thomas D. Bucheli
    2020 - Science of The Total Environment, in press

    Abstract: 

    Implementing advanced wastewater treatment (WWT) to eliminate organic micropollutants (OMPs) is a necessary step to protect vulnerable freshwater ecosystems and water resources. To this end, sorption of OMP by activated carbon (AC) is one viable technology among others. However, conventional AC production based on fossil precursor materials causes environmental pollution, including considerable emissions of greenhouse gases. In this study, we produced activated biochar (AB) from wood and woody residues by physical activation and evaluated their capability to eliminate OMPs in treated wastewater. Activated biochar produced under optimized conditions sorbed 15 model OMPs, of which most were dissociated at circumneutral pH, to the same or higher extent than commercial AC used as a reference. While wood quality played a minor role, the dosage of the activation agent was the main parameter controlling the capacity of ABs to eliminate OMP. Our results highlight the possibility for local production of AB from local wood or woody residues as a strategy to improve WWT avoiding negative side effects of conventional AC production.

Book chapters and other publications

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