Publications

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Publications in peer reviewed journals

27 Publications found
  • A critical evaluation of nanopesticides and nanofertilizers against their conventional analogues

    Melanie Kah, Rai Singh Kookana, Alexander Gogos, Thomas Daniel Bucheli
    2018 - Nature Nanotechnology, 8: 677-684

    Abstract: 

    Among a wide range of possible applications of nanotechnology in agriculture, there has been a particular interest in developing novel nanoagrochemicals. While some concerns have been expressed regarding altered risk profile of the new products, many foresee a great potential to support the necessary increase in global food production in a sustainable way. A critical evaluation of nanoagrochemicals against conventional analogues is essential to assess the associated benefits and risks. In this assessment, recent literature was critically analysed to determine the extent to which nanoagrochemicals differ from conventional products. Our analysis was based on 78 published papers and shows that median gain in efficacy relative to conventional products is about 20–30%. Environmental fate of agrochemicals can be altered by nanoformulations, but changes may not necessarily translate in a reduction of the environmental impact. Many studies lacked nano-specific quality assurance and adequate controls. Currently, there is no comprehensive study in the literature that evaluates efficacy and environmental impact of nanoagrochemicals under field conditions. This is a crucial knowledge gap and more work will thus be necessary for a sound evaluation of the benefits and new risks that nanoagrochemicals represent relative to existing products.

  • Comparison of Sorption to Carbon-Based Materials and Nanomaterials Using Inverse Liquid Chromatography

    Florian Metzelder, Matin Funck, Thorsten Hüffer, Torsten C. Schmidt
    2018 - Environmental Science & Technology, 1: 9731-9740

    Abstract: 

    Sorption studies of carbon-based materials and nanomaterials are typically conducted using batch experiments, but the analysis of weakly sorbing compounds may be challenging. Column chromatography represents a promising complement as higher sorbent to solution ratios can be applied. The sorbent is packed in a column, and sorption data are calculated by relating sorbate retention times to that of a nonretarded tracer. In this study, sorption of heterocyclic organic compounds (pyrazole, pyrrole, furan, and thiophene) by carbon-based materials (activated carbon, biochar, and graphite) and nanomaterials (functionalized carbon nanotubes and graphene platelets) was compared for the first time using column chromatography. D2O was used as nonretarded tracer. Sorption isotherms were nonlinear and described well by the Freundlich model. Sorption differed between the materials regarding determined Freundlich coefficients (Kf) by more than two orders of magnitude for isotherms in a similar concentration range. Normalization of Kf with the surface area of the sorbent significantly reduced but did not remove the differences between the sorbents. Overall, column chromatography represents the opportunity to study sorption of weakly sorbing compounds to diverse carbon-based sorbent materials with a single experimental approach, which is challenging in batch experiments because of the very different sorption properties of some sorbent materials.

  • Constraints to Synergistic Fe Mobilization from Calcareous Soil by a Phytosiderophore and a Reductant

    Walter Schenkeveld, Stephan M. Kraemer
    2018 - Soil Systems, 4: 67

    Abstract: 

    Synergistic effects between ligand- and reductant-based Fe acquisition strategies can enhance the mobilization of Fe, but also of competing metals from soil. For phytosiderophores, this may alter the time and concentration window of Fe uptake during which plants can benefit from elevated Fe concentrations. We examined how the size of this window is affected by the ligand and reductant concentration and by non-simultaneous addition. To this end, a series of kinetic batch experiments was conducted with a calcareous clay soil to which the phytosiderophore 2′-deoxymugineic acid (DMA) and the reductant ascorbate were added at various concentrations, either simultaneously or with a one- or two-day lag time. Both simultaneous and non-simultaneous addition of the reductant and the phytosiderophore induced synergistic Fe mobilization. Furthermore, initial Fe mobilization rates increased with increasing reductant and phytosiderophore concentrations. However, the duration of the synergistic effect and the window of Fe uptake decreased with increasing reductant concentration due to enhanced competitive mobilization of other metals. Rate laws accurately describing synergistic mobilization of Fe and other metals from soil were parameterized. Synergistic Fe mobilization may be vital for the survival of plants and microorganisms in soils of low Fe availability. However, in order to optimally benefit from these synergistic effects, exudation of ligands and reductants in the rhizosphere need to be carefully matched.

  • Data on sorption of organic compounds by aged polystyrene microplastic particles

    Thorsten Hüffer, Anne-Katrin Weniger, Thilo Hofmann
    2018 - Data in Brief, 474-479

    Abstract: 

    This article contains data on experimental sorption isotherms of 21 probe sorbates by aged polystyrene microplastics. The polymeric particles were subjected to an UV-induced photo-oxidation procedure using hydrogen peroxide in a custom-made aging chamber. Sorption data were obtained for aged particles. The experimental sorption data was modelled using both single- and poly-parameter linear free-energy relationships. For discussion and interpretation of the presented data, refer to the research article entitled “Sorption of organic compounds by aged polystyrene microplastic particles” (Hüffer et al., 2018) [1].

  • Development of a versatile analytical protocol for the comprehensive determination of the elemental composition of smartphone compartments on the example of printed circuit boards

    B. Bookhagen, W. Obermaier, C. Opper, C. Koeberl, Thilo Hofmann, T. Prohaska J. Irrgeher
    2018 - Analytical Methods, 3: 3864-3871

    Abstract: 

    A versatile approach to determining the elemental content of more than 50 elements in different components of electronic devices on the example of smartphones was developed. The analytical protocol is based on accurate disassembly of smartphones, a single processing microwave-assisted acid digestion followed by ICP-OES and ICP-MS measurements. Method optimization and validation were performed using the certified reference material ERM®-EZ505 electronic scrap. Combined uncertainties revealed measurement uncertainty and sample heterogeneity as main contributors. The contents of up to 57 elements could be quantified in the certified reference material ERM®-EZ505 electronic scrap. The results of the certified elements Au, Be, Cu, In, Ni, Pd, and Pt overlapped within their uncertainties with the certified range and revealed recoveries of 100% ± 16%. Only Ag shows incomplete recoveries (75% ± 35%). The validated method was applied to all metal-containing components of selected smartphones, excluding batteries. The contents of up to 57 elements could be quantified and are presented exemplarily for printed circuit boards, which represent the most complex components in the investigated smartphones and thus limit the capability of the method. The ten most abundant elements in decreasing order are Cu, Fe, Si, Ni, Sn, Zn, Ba, Al, Cr, Ti, which comprise approx. 80% of the weight of the printed circuit boards. The method allows for the determination of metal content in various parts of modern smartphones, providing the basis for the estimation and prediction of future metal usage and thus the comprehensive investigation of recycling and circular economy aspects.

  • Effect of field site hydrogeochemical conditions on the corrosion of milled zerovalent iron particles and their dechlorination efficiency

    Milica Velimirovic, Melanie Auffan, Luca Carniato, Vesna Micić, Doris Schmid, Stephan Wagner, Daniel Borschneck, Olivier Proux, Frank von der Kammer, Thilo Hofmann
    2018 - Science of The Total Environment, 1619-1627

    Abstract: 

    Milled zerovalent iron (milled ZVI) particles have been recognized as a promising agent for groundwater remediation because of (1) their high reactivity with chlorinated aliphatic hydrocarbons, organochlorine pesticides, organic dyes, and a number of inorganic contaminants, and (2) a possible greater persistance than the more extensively investigated nanoscale zerovalent iron. We have used laboratory-scale batch degradation experiments to investigate the effect that hydrogeochemical conditions have on the corrosion of milled ZVI and on its ability to degrade trichloroethene(TCE). The observed pseudo first-order degradation rate constants indicated that the degradation of TCE by milled ZVI is affected by groundwater chemistry. The apparent corrosion rates of milled ZVI particles were of the same order of magnitude for hydrogeochemical conditions representative for two contaminated field sites (133–140 mmol kg− 1 day− 1, indicating a milled ZVI life-time of 128–135 days). Sulfate enhances milled ZVI reactivity by removing passivating iron oxides and hydroxides from the Fe0 surface, thus increasing the number of reactive sites available. The organic matter content of 1.69% in the aquifer material tends to suppress the formation of iron corrosion precipitates. Results from scanning electron microscopy, X-ray diffraction, and iron K-edge X-ray adsorption spectroscopy suggest that the corrosion mechanisms involve the partial dissolution of particles followed by the formation and surface precipitation of magnetite and/or maghemite. Numerical corrosion modeling revealed that fitting iron corrosion rates and hydrogen inhibitory terms to hydrogen and pH measurements in batch reactors can reduce the life-time of milled ZVI particles by a factor of 1.2 to 1.7.

  • Emission and fate modelling framework for engineered nanoparticles in urban aquatic systems at high spatial and temporal resolution

    Prado Domercq, Antonia Praetorius, Alistair B. A. Boxall
    2018 - Environmental Science: Nano, 2: 533-543

    Abstract: 

    Trends in global urbanization and technology development have raised concerns about the associated increase in emissions to the environment, including novel contaminants such as engineered nanoparticles (ENPs). The assessment of these emissions in urban systems requires modelling approaches that integrate the complexity of urban environments as well as the high spatial and temporal variability of contaminant emissions. ENPs are emitted to urban surface waters through a variety of point and diffuse sources, with these emissions being driven by weather, usage patterns and population density. While the potential environmental and health impacts of ENPs are still not fully understood, understanding the spatial and temporal distribution of ENPs at the local scale will help to inform risk assessment. In this paper, we propose a novel modelling approach for estimating the exposure of ENPs in surface waters of urban systems. An integrative modelling framework combining an emission and a fate model for ENPs with high spatial and temporal resolution is presented and strategies for data gathering and the handling of knowledge gaps are discussed. Our framework is capable of identifying local emission hot spots and predicting exposure across a city, while generating information on the final speciation of the emitted ENPs (nano form, aggregates and other transformation products) within the studied environmental compartments over time.

  • Environmental fate of nanopesticides: durability, sorption and photodegradation of nanoformulated clothianidin

    Melanie Kah, Helene Walch, Thilo Hofmann
    2018 - Environmental Science: Nano, 4: 882-889

    Abstract: 

    A lot of research efforts are currently dedicated to the development of nano-enabled agrochemicals. Knowledge about their environmental behaviour is however scarce, which impedes the assessment of the new risk and benefits relative to currently used agrochemicals. With the aim to advance our understanding of the fate of nanopesticides in the environment and support the development of robust exposure assessment procedures, the main objectives of the study were to (i) investigate the extent to which three nanoformulations can affect the photodegradation and sorption of the insecticide clothianidin, and (ii) evaluate various approaches to estimate durability, a key parameter for the exposure assessment of nanopesticides. The nanoformulations increased the photodegradation half-life in water by a maximum of 21% relative to the conventional formulation. Sorption to soil was investigated by two methods and over time, and results show that sorption was increased by up to 51% and 10%, relative to unformulated clothianidin and the commercial formulation, respectively. Our results generally indicate that nanoformulations may have a greater impact on the fate of pesticide active ingredients than commercial formulations. It is important to note however that differences in fate parameters were generally very moderate, including in realistic worst-case conditions (high pesticide concentration and ionic strength). Our results collectively suggest that clothianidin was rapidly released from the nanocarrier systems and that the durability of the three nanoformulations would be short in water as well as in soil environments (including under realistic soil to solution ratio). The durability of nanoformulations after their application in the environment is an essential parameter that needs to be characterised for the development as well as for the evaluation of nano-enabled agrochemicals. This study illustrates how performances of nano-enabled products can be critically benchmarked against existing products to support an objective assessment of new environmental risks and benefits. In this context, the fate of the nanocarrier system is of great interest and should be the topic of further research.

  • Environmental Impacts by Fragments Released from Nanoenabled Products: A Multiassay, Multimaterial Exploration by the SUN Approach

    Mnica J.B. Amorim, Sijie Lin, Karsten Schlich, Jos M. Navas, Andrea Brunelli, Nicole Neubauer, Klaus Vilsmeier, Anna L. Costa, Andreas Gondikas, Tian Xia, Liliana Galbis, Elena Badetti, Antonio Marcomini, Danail Hristozov, Frank von der Kammer, Kerstin Hund-Rinke, Janeck J. Scott-Fordsmand, Andr Nel, Wendel Wohlleben
    2018 - Environmental Science & Technology, 3: 1514-1524

    Abstract: 

    Nanoenabled products (NEPs) have numerous outdoor uses in construction, transportation or consumer scenarios, and there is evidence that their fragments are released in the environment at low rates. We hypothesized that the lower surface availability of NEPs fragment reduced their environmental effects with respect to pristine nanomaterials. This hypothesis was explored by testing fragments generated by intentional micronisation (“the SUN approach”; Nowack et al. Meeting the Needs for Released Nanomaterials Required for Further Testing: The SUN Approach. Environmental Science & Technology2016 (50), 2747). The NEPs were composed of four matrices (epoxy, polyolefin, polyoxymethylene, and cement) with up to 5% content of three nanomaterials (carbon nanotubes, iron oxide, and organic pigment). Regardless of the type of nanomaterial or matrix used, it was observed that nanomaterials were only partially exposed at the NEP fragment surface, indicating that mostly the intrinsic and extrinsic properties of the matrix drove the NEP fragment toxicity. Ecotoxicity in multiple assays was done covering relevant media from terrestrial to aquatic, including sewage treatment plant (biological activity), soil worms (Enchytraeus crypticus), and fish (zebrafish embryo and larvae and trout cell lines). We designed the studies to explore the possible modulation of ecotoxicity by nanomaterial additives in plastics/polymer/cement, finding none. The results support NEPs grouping by the matrix material regarding ecotoxicological effect during the use phase. Furthermore, control results on nanomaterial-free polymer fragments representing microplastic had no significant adverse effects up to the highest concentration tested.

  • Environmental transformation of natural and engineered carbon nanoparticles and implications for the fate of organic contaminants

    Gabriel Sigmund, Chuanjia Jiang, Thilo Hofmann, Wei Chen
    2018 - Environmental Science: Nano, 1: 2500-2518

    Abstract: 

    Environmental transformation of carbon nanoparticles can significantly affect their transport, fate, and effects. The last decade of environmental nano-science has often focused on understanding the behavior of well-defined engineered carbon nanoparticles (eCNPs) in the natural environment. However, more complex pyrogenic/petrogenic carbon nanoparticles (pCNPs), including those derived from soot, fossil coal, wildfire charcoal, and biochar, are more than four orders of magnitude more abundant in the environment. This paper aims to review findings from investigations into eCNPs and to consider their transferability to pCNPs, in order to improve our understanding of pCNPs and identify gaps in our knowledge. Findings from previous investigations into the chemical, physical and biological transformation of larger carbonaceous particles, as well as of eCNPs, can help us to understand the transformation of pCNPs. The transformation of soot during atmospheric transport is relatively well documented, whereas the transformation of pCNPs in soil, sediment, and aqueous systems remains poorly understood. To bridge findings on particulate transport, contaminant binding, and contaminant transformation from eCNPs to pCNPs, the complex compositions of pCNPs need to be taken into account. We therefore suggest that future research on pCNP transformation should focus on changes in intrinsic porosity and on interactions with non-carbonized phases, tar phases, and mineral phases, as well as with organo-mineral complexes in soils, sediments and water bodies.

  • Fe(II)-Catalyzed Ligand-Controlled Dissolution of Iron(hydr)oxides

    Jagannath Biswakarma, Kyounglim Kang, Susan C. Borowski, Walter D.C. Schenkeveld, Stephan M. Kraemer, Janet G. Hering, Stephan J. Hug
    2018 - Environmental Science & Technology, 1: 88-97

    Abstract: 

    Dissolution of iron(III)phases is a key process in soils, surface waters, and the ocean. Previous studies found that traces of Fe(II) can greatly increase ligand controlled dissolution rates at acidic pH, but the extent that this also occurs at circumneutral pH and what mechanisms are involved are not known. We addressed these questions with infrared spectroscopy and 57Fe isotope exchange experiments with lepidocrocite (Lp) and 50 μM ethylenediaminetetraacetate (EDTA) at pH 6 and 7. Addition of 0.2–10 μM Fe(II) led to an acceleration of the dissolution rates by factors of 7–31. Similar effects were observed after irradiation with 365 nm UV light. The catalytic effect persisted under anoxic conditions, but decreased as soon as air or phenanthroline was introduced. Isotope exchange experiments showed that added 57Fe remained in solution, or quickly reappeared in solution when EDTA was added after 57Fe(II), suggesting that catalyzed dissolution occurred at or near the site of 57Fe incorporation at the mineral surface. Infrared spectra indicated no change in the bulk, but changes in the spectra of adsorbed EDTA after addition of Fe(II) were observed. A kinetic model shows that the catalytic effect can be explained by electron transfer to surface Fe(III) sites and rapid detachment of Fe(III)EDTA due to the weaker bonds to reduced sites. We conclude that the catalytic effect of Fe(II) on dissolution of Fe(III)(hydr)oxides is likely important under circumneutral anoxic conditions and in sunlit environments.

  • Influence of compost and biochar on microbial communities and the sorption/degradation of PAHs and NSO-substituted PAHs in contaminated soils

    Gabriel Sigmund, Caroline Poyntner, Guadalupe Piñar, Melanie Kah, Thilo Hofmann
    2018 - Journal of Hazardous Materials, 107-113

    Abstract: 

    Diffusely contaminated soils often remain untreated as classical remediation approaches would be disproportionately expensive. Adding compost can accelerate the biodegradation of organic contaminants and adding biochar can immobilize contaminants through sorption. The combined use of compost and biochar to reduce polycyclic aromatic hydrocarbon (PAH) and NSO-substituted PAH contamination has, however, not previously been systematically investigated. We have therefore investigated the processes involved (i) through sorption batch experiments, (ii) by monitoring changes in bacterial, fungal and archaeal communities using denaturing gradient gel electrophoresis, and (iii) through degradation experiments with fluorene, phenanthrene, pyrene, carbazole, dibenzothiophene, and dibenzofuran. Sorption coefficients for organic contaminants in soils increased tenfold following 10% compost addition and up to a hundredfold with further addition of 5% biochar. The rate of PAH and NSO-PAH degradation increased up to twofold following compost addition despite increased sorption, probably due to the introduction of additional microbial species into the autochthonous soil communities. In contrast, degradation of PAHs and NSO-PAHs in soil-compost-biochar mixtures slowed down up to tenfold due to the additional sorption, although some degradation still occurred. The combined use of biochar and compost may therefore provide a strategy for immobilizing PAHs and NSO-PAHs and facilitating degradation of remaining accessible contaminant fractions.

  • Low Fe(II) Concentrations Catalyze the Dissolution of Various Fe(III) (hydr)oxide Minerals in the Presence of Diverse Ligands and over a Broad pH Range

    Kyounglim Kang, Walter D. C. Schenkeveld, Jagannath Biswakarma, Susan C. Borowski, Stephan J. Hug, Janet G. Hering, Stephan M. Kraemer
    2018 - Environmental Science & Technology, 1: 98-107

    Abstract: 

    Dissolution of Fe(III) (hydr)oxide minerals by siderophores (i.e., Fe-specific, biogenic ligands) is an important step in Fe acquisition in environments where Fe availability is low. The observed coexudation of reductants and ligands has raised the question of how redox reactions might affect ligand-controlled (hydr)oxide dissolution and Fe acquisition. We examined this effect in batch dissolution experiments using two structurally distinct ligands (desferrioxamine B (DFOB) and N,N′-di(2-hydroxybenzyl)ethylene-diamine-N,N′-diacetic acid (HBED)) and four Fe(III) (hydr)oxide minerals (lepidocrocite, 2-line ferrihydrite, goethite and hematite) over an environmentally relevant pH range (4–8.5). The experiments were conducted under anaerobic conditions with varying concentrations of (adsorbed) Fe(II) as the reductant. We observed a catalytic effect of Fe(II) on ligand-controlled dissolution even at submicromolar Fe(II) concentrations with up to a 13-fold increase in dissolution rate. The effect was larger for HBED than for DFOB. It was observed for all four Fe(III) (hydr)oxide minerals, but it was most pronounced for goethite in the presence of HBED. It was observed over the entire pH range with the largest effect at pH 7 and 8.5, where Fe deficiency typically occurs. The occurrence of this catalytic effect over a range of environmentally relevant conditions and at very low Fe(II) concentrations suggests that redox-catalyzed, ligand-controlled dissolution may be significant in biological Fe acquisition and in redox transition zones.

  • Mechanisms of (photo)toxicity of TiO2 nanomaterials (NM103, NM104, NM105): using high-throughput gene expression in Enchytraeus crypticus

    Susana I. L. Gomes, Carlos P. Roca, Frank von der Kammer, Janeck J. Scott-Fordsmand, Mónica J. B. Amorim
    2018 - Nanoscale, 10: 21960-21970

    Abstract: 

    Titanium dioxide (TiO2) based nanomaterials (NMs) are among the most produced NMs worldwide. When irradiated with light, particularly UV, TiO2 is photoactive, a property that is explored for several purposes. There are an increasing number of reports on the negative effects of photoactivated TiO2 on non-target organisms. We have here studied the effect of a suite of reference type TiO2 NMs (i.e. NM103, NM104, and NM105 and compared these to the bulk) with and without UV radiation to the oligochaete Enchytraeus crypticus. High-throughput gene expression was used to assess the molecular mechanisms, while also anchoring it to the known effects at the organism level (i.e., reproduction). Results showed that the photoactivity of TiO2 (UV exposed) played a major role in enhancing TiO2 toxicity, activating the transcription of oxidative stress, lysosome damage and apoptosis mechanisms. For non-UV activated TiO2, where toxicity at the organism level (reproduction) was lower, results showed potential for long-term effects (i.e., mutagenic and epigenetic). NM specific mechanisms were identified: NM103 affected transcription and translation, NM104_UV negatively affected the reproductive system/organs, and NM105_UV activated superoxide anion response. Results provided mechanistic information on UV-related phototoxicity of TiO2 materials and evidence for the potential long-term effects.

  • Mercury isotope signatures of digests and sequential extracts from industrially contaminated soils and sediments

    Andrew R.C. Grigg, Ruben Kretzschmar, Robin S. Gilli, Jan G. Wiederhold
    2018 - Science of The Total Environment, 1344-1354

    Abstract: 

    Environmental mercury (Hg) pollution is a matter of global concern. Mercury speciation controls its environmental behaviour, and stable isotope ratios can potentially trace Hg movement through environmental compartments. Here we investigated Hg in industrially contaminated soils and sediments (Visp, Valais, Switzerland) using concentration and stable isotope analysis (CV-MC-ICP-MS) of total digests, and a four-step sequential extraction procedure. The sequential extraction employed (1) water (labile Hg species), (2) NaOH or Na4P2O7 (organically-bound Hg), (3) hydroxylamine-HCl (Hg bound to Mn and Fe (oxyhydr)oxides), and (4) aqua regia (residual Hg pools). The majority of Hg was extracted in step 4 and up to 36% in step 2. Mercury bound to organic matter was the dominant source of Hg in water, NaOH and Na4P2O7 extracts. Sulfides and colloidal oxide minerals were possible additional sources of Hg in some samples. The inconsistent comparative performance of NaOH and Na4P2O7 extractions showed that these classical extractants may not extract Hg exclusively from the organically-bound pool. Samples taken at the industrial facility displayed the greatest isotopic variation (δ202Hg: −0.80‰ ± 0.14‰ to 0.25‰ ± 0.13‰, Δ199Hg: −0.10‰ ± 0.03‰ to 0.02‰ ± 0.03‰; all 2SD) whereas downstream of the facility there was much less variation around average values of δ202Hg = −0.47‰ ± 0.11‰ and Δ199Hg = −0.05‰ ± 0.03‰ (1SD, n = 19). We interpret the difference as the result of homogenisation by mixing of canal sediments containing Hg from the various sources at the industrial facility with preservation of the mixed industrial Hg signature downstream. In contrast to previous findings, Hg isotopes in the sequential extracts were largely similar to one another (2SD < 0.14‰), likely demonstrating that the Hg speciation was similar among the extracts. Our results reveal that Hg resides in relatively stable soil pools which record an averaged isotope signature of the industrial sources, potentially facilitating source tracing studies with Hg isotope signatures at larger spatial scales further downstream.

  • Modeling Subsurface Fate of S-Metolachlor and Metolachlor Ethane Sulfonic Acid in the Westliches Leibnitzer Feld Aquifer

    Hans Kupfersberger, Gernot Klammler, Andrea Schumann, Lisa Brckner, Melanie Kah
    2018 - Vadose Zone Journal, 1: in press

    Abstract: 

    Pesticides and their metabolites have been increasingly detected in groundwater bodies in southeastern Austria in recent years. The main objective of this study was to model the fate of the herbicide S-metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-[(1S)-2-methoxy-1-methylethyl]acetamide; SMET) and the main metabolite metolachlor ethane sulfonic acid (MESA) at the Westliches Leibnitzer Feld (WLF) aquifer. For this purpose, a modeling approach based on coupling the one-dimensional vadose zone model PEARL and the two-dimensional groundwater flow and solute transport model FEFLOW was developed. To calibrate the one-dimensional pesticide fate model, we used leachate concentrations of SMET and MESA from lysimeter experiments. Additionally, samples of representative soil types in the WLF aquifer were analyzed to infer SMET- and MESA-specific fate parameters (e.g., half-life DT50, Freundlich sorption coefficient Kfoc), which were used for the PEARL model. The results show that using SMET fate parameters derived from the lysimeter data considerably improved the fit of the simulation results with the field observations compared with the application of standard laboratory-derived fate parameters accounting for soil type differences. Although locally an overestimation of the monitoring data prevailed, the description of the subsurface fate of pesticides will improve the interpretation of concentration data and the design of mitigation measures.

  • Optimising the transport properties and reactivity of microbially-synthesised magnetite for in situ remediation

    Nimisha Joshi, Feixue Liu, Mathew Paul Watts, Heather Williams, Victoria S. Coker, Doris Schmid, Thilo Hofmann, Jonathan R. Lloyd
    2018 - Scientific Reports, 1: in press

    Abstract: 

    Engineered nanoparticles offer the potential for remediation of land and water that has been contaminated by organics and metals. Microbially synthesized nano-scale magnetite, prepared from Fe(III) oxides by subsurface Fe(III)-reducing bacteria, offers a scalable biosynthesis route to such a nano-scale remediation reagent. To underpin delivery of “bionanomagnetite” (BNM) nanomaterial during in situ treatment options, we conducted a range of batch and column experiments to assess and optimise the transport and reactivity of the particles in porous media. Collectively these experiments, which include state of the art gamma imaging of the transport of 99m Tc-labelled BNM in columns, showed that non-toxic, low cost coatings such as guar gum and salts of humic acid can be used to enhance the mobility of the nanomaterial, while maintaining reactivity against target contaminants. Furthermore, BNM reactivity can be enhanced by the addition of surface coatings of nano-Pd, extending the operational lifetime of the BNM, in the presence of a simple electron donor such as hydrogen or formate.

  • Proposal for a tiered dietary bioaccumulation testing strategy for engineered nanomaterials using fish

    Richard D. Handy, Jukka Ahtiainen, Jos Mara Navas, Greg Goss, Eric A. J. Bleeker, Frank von der Kammer
    2018 - Environmental Science: Nano, 9: 2030-2046

    Abstract: 

    The scientific community has invested effort into standardising methodologies for the regulatory ecotoxicity testing of engineered nanomaterials (ENMs), but the practical requirements for bioaccumulation testing of ENMs have been given less attention. A strategy for a tiered approach to bioaccumulation testing of ENMs using fish is proposed, with recommendations for its implementation by regulatory agencies. The strategy recognises that testing the many shapes, sizes and chemistries of ENMs as new substances in vivo would be an unrealistic workload. The approach therefore includes grouping/read-across methods and tools to screen out ENMs of negligible/low bioaccumulation potential. The strategy proposes reductions of animal use for in vivo testing and with greater consideration of in vitro methods. The first tier uses dissolution in water or lipids and particle settling rates as environmental chemistry triggers for ‘ENMs of concern’. The first tier also involves a weight of evidence from these tests, plus using existing data sets from selected literature that meet data quality criteria for ENMs. Tier 2 involves new data generation using in silico models now being validated for ENMs, including QSARs and systems biology tools. Tier 2 also includes using existing experimental data, and an option to collect new data. These data can be on soils/sediments, microbial degradation, and bioaccumulation studies on invertebrates or fish cell lines. In tier 3, an in chemico digestibility assay simulating the gut lumen of fish is proposed to identify the bioaccessible fractions from an oral exposure to ENMs. If the digestibility assay is positive, then in vitro gut sacs from rainbow trout can be used to confirm accumulation by the gut mucosa. Only if both these tests in tier 3 are positive would the work proceed to the final in vivo test (tier 4) which is essentially the OECD TG 305 method for dietary bioaccumulation testing using fish, with some caveats and recommendations for ENMs. These include considerations of terminology, how to prepare contaminated food for dietary exposures, the additional controls and endpoints for ENMs, measuring ENMs in food and tissues to confirm the exposure, and the limitations of any subsequent calculation of the bioaccumulation potential.

  • Scientific rationale for the development of an OECD test guideline on engineered nanomaterial stability

    Fazel Abdolahpur Monikh, Antonia Praetorius, Andrea Schmid, Philipp Kozin, Boris Meisterjahn, Ekaterina Makarova, Thilo Hofmann, Frank von der Kammer
    2018 - NanoImpact, 42-50

    Abstract: 

    Standardized methods for assessing the behaviour of engineered nanomaterials(ENMs) under relevant environmental conditions are an important part of ENM risk assessment. Existing assays, often developed for traditional chemicals, are frequently not applicable to ENMs, which present special challenges due to their particulate nature and complex intrinsic and extrinsic properties. Here we present the development of the novel OECD test guideline (TG) No. 318 for studying the “dispersion stability of nanomaterials in simulated environmental media”. We discuss the rationalization of the test design and required simplifications to develop a test, which can be executed in standard laboratories on a routine basis at reasonable costs. The relevance of the test for capturing ENM stability in surface waters is ensured by a strategic selection of adequate test media and testing scheme. As an example, we present data of a full test performed according to the new OECD TG using NM 105 as a representative TiO2 ENM. Limitations of the test in terms of scarce kinetic information and a focus on homo- instead of heteroaggregation are discussed. The developed OECD Test No. 318 represents the first standardized assay for ENMs using an operationally defined testing scheme capable of systematically comparing different ENMs in terms of their dispersion stability under environmentally relevant conditions. It will provide crucial data to inform risk assessment and regulation and can be adapted to different types of test media if needed.

  • Sorption of organic compounds by aged polystyrene microplastic particles

    Thorsten Hüffer, Anne-Katrin Weniger, Thilo Hofmann
    2018 - Environmental Pollution, 218-225

    Abstract: 

    Microplastics that are released into the environment undergo aging and interact with other substances such as organic contaminants. Understanding the sorption interactions between aged microplastics and organic contaminants is therefore essential for evaluating the impact of microplastics on the environment. There is little information available on how the aging of microplastics affects their sorption behavior and other properties. We have therefore investigated the effects of an accelerated UV-aging procedure on polystyrene microplastics, which are used in products such as skin cleaners and foams. Physical and chemical particle characterizations showed that aging led to significant surface oxidation and minor localized microcrack formation. Sorption coefficients of organic compounds by polystyrene microplastics following aging were up to one order of magnitude lower than for pristine particles. Sorption isotherms were experimentally determined using a diverse set of probe sorbates covering a variety of substance classes allowing an in-depth evaluation of the poly-parameter linear free-energy relationship (ppLFER) modelling used to investigate the contribution of individual molecular interactions to overall sorption. The ppLFER modelling was validated using internal cross-validation, which confirmed its robustness. This approach therefore yields improved estimates of the interactions between aged polystyrene microplastics and organic contaminants.

  • Sorption of organic substances to tire wear materials: Similarities and differences with other types of microplastic

    Thorsten Hüffer, Stephan Wagner, Thorsten Reemtsma, Thilo Hofmann
    2018 - TrAC Trends in Analytical Chemistry, 392-401

    Abstract: 

    Tire materials are a significant proportion of the (micro)plastics in the environment that until today have been clearly overlooked. These materials are released into the environment, either unintentionally as an abrasion product from tire wear, that reaches the environment via road runoff, or intentionally as, for example, shredded “tire crumble rubber” used as filling material for playgrounds. Although there are a few estimates available the amount of tire-wear material to be found in aquatic environments, investigations on the fate tire materials and especially their interaction with organic substances are missing. Although the sorption processes associated with the complex constituents of tires are an important aspect of any environmental risk assessment for tire-wear materials, they have yet to be thoroughly investigated. In this review we elucidate the sorption properties of the polymeric rubbers and carbon black that form the main components of tires, within the context of current microplastic research.

  • Sorption to soil, biochar and compost: is prediction to multicomponent mixtures possible based on single sorbent measurements?

    Melanie Kah, Gabriel Sigmund, Pedro Luis Manga Chavez, Lucie Bielská, Thilo Hofmann
    2018 - PeerJ, 673 —692

    Abstract: 

    Amendment with biochar and/or compost has been proposed as a strategy to remediate soil contaminated with low levels of polycyclic aromatic hydrocarbons. The strong sorption potential of biochar can help sequestering contaminants while the compost may promote their degradation. An improved understanding of how sorption evolves upon soil amendment is an essential step towards the implementation of the approach. The present study reports on the sorption of pyrene to two soils, four biochars and one compost. Detailed isotherm analyzes across a wide range of concentration confirmed that soil amendments can significantly increase the sorption of pyrene. Comparisons of data obtained by a classical batch and a passive sampling method suggest that dissolved organic matter did not play a significant role on the sorption of pyrene. The addition of 10% compost to soil led to a moderate increase in sorption (<2-fold), which could be well predicted based on measurements of sorption to the individual components. Hence, our result suggest that the sorption of pyrene to soil and compost can be relatively well approximated by an additive process. The addition of 5% biochar to soil (with or without compost) led to a major increase in the sorption of pyrene (2.5–4.7-fold), which was, however, much smaller than that suggested based on the sorption measured on the three individual components. Results suggest that the strong sorption to the biochar was attenuated by up to 80% in the presence of soil and compost, much likely due to surface and pore blockage. Results were very similar in the two soils considered, and collectively suggest that combined amendments with compost and biochar may be a useful approach to remediate soils with low levels of contamination. Further studies carried out in more realistic settings and over longer periods of time are the next step to evaluate the long term viability of remediation approaches based on biochar amendments.

  • Structure and reactivity of oxalate surface complexes on lepidocrocite derived from infrared spectroscopy, DFT-calculations, adsorption, dissolution and photochemical experiments

    Susan C. Borowski, Jagannath Biswakarma, Kyounglim Kang, Walter D.C. Schenkeveld, Janet G. Hering, James D. Kubicki, Stephan M. Kraemer, Stephan J. Hug
    2018 - Geochimica et Cosmochimica Acta, 244-262

    Abstract: 

    Oxalate, together with other ligands, plays an important role in the dissolution of iron(hdyr)oxides and the bio-availability of iron. The formation and properties of oxalate surface complexes on lepidocrocite were studied with a combination of infrared spectroscopy (IR), density functional theory (DFT) calculations, dissolution, and photochemical experiments. IR spectra measured as a function of time, concentration, and pH (50–200 µM oxalate, pH 3–7) showed that several surface complexes are formed at different rates and in different proportions. Measured spectra could be separated into three contributions described by Gaussian line shapes, with frequencies that agreed well with the theoretical frequencies of three different surface complexes: an outer-sphere complex (OS), an inner-sphere monodentate mononuclear complex (MM), and a bidentate mononuclear complex (BM) involving one O atom from each carboxylate group. At pH 6, OS was formed at the highest rate. The contribution of BM increased with decreasing pH. In dissolution experiments, lepidocrocite was dissolved at rates proportional to the surface concentration of BM, rather than to the total adsorbed concentration. Under UV-light (365 nm), BM was photolyzed at a higher rate than MM and OS. Although the comparison of measured spectra with calculated frequencies cannot exclude additional possible structures, the combined results allowed the assignment of three main structures with different reactivities consistent with experiments. The results illustrate the importance of the surface speciation of adsorbed ligands in dissolution and photochemical reactions.

  • Tire wear particles in the aquatic environment - A review on generation, analysis, occurrence, fate and effects

    Wagner S, Thorsten Hüffer, Klöckner P, Wehrhahn M, Thilo Hofmann, Reemtsma T
    2018 - Water Research, 83-100

    Abstract: 

    Tire wear particles (TWP), generated from tire material during use on roads have gained increasing attention as part of organic particulate contaminants, such as microplastic, in aquatic environments. The available information on properties and generation of TWP, analytical techniques to determine TWP, emissions, occurrence and behavior and ecotoxicological effects of TWP are reviewed with a focus on surface water as a potential receptor. TWP emissions are traffic related and contribute 5–30% to non-exhaust emissions from traffic. The mass of TWP generated is estimated at 1,327,000 t/a for the European Union, 1,120,000 t/a for the United States and 133,000 t/a for Germany. For Germany, this is equivalent to four times the amount of pesticides used. The mass of TWP ultimately entering the aquatic environment strongly depends on the extent of collection and treatment of road runoff, which is highly variable. For the German highways it is estimated that up to 11,000 t/a of TWP reach surface waters. Data on TWP concentrations in the environment, including surface waters are fragmentary, which is also due to the lack of suitable analytical methods for their determination. Information on TWP properties such as density and size distribution are missing; this hampers assessing the fate of TWP in the aquatic environment. Effects in the aquatic environment may stem from TWP itself or from compounds released from TWP. It is concluded that reliable knowledge on transport mechanism to surface waters, concentrations in surface waters and sediments, effects of aging, environmental half-lives of TWP as well as effects on aquatic organisms are missing. These aspects need to be addressed to allow for the assessment of risk of TWP in an aquatic environment.

  • Transformations of Nanoenabled Copper Formulations Govern Release, Antifungal Effectiveness, and Sustainability throughout the Wood Protection Lifecycle

    Daniele Pantano, Nicole Neubauer, Jana Navratilova, Lorette Scifo, Chiara Civardi, Vicki Stone, Frank von der Kammer, Philipp Müller, Marcos Sanles Sobrido, Bernard Angeletti, Jerome Rose, Wendel Wohlleben
    2018 - Environmental Science & Technology, 3: 1128-1138

    Abstract: 

    Here we compare the standard European benchmark of wood treatment by molecularly dissolved copper amine (Cu–amine), also referred to as aqueous copper amine (ACA), against two nanoenabled formulations: copper(II)oxide nanoparticles (CuO NPs) in an acrylic paint to concentrate Cu as a barrier on the wood surface, and a suspension of micronized basic copper carbonate (CuCO3·Cu(OH)2) for wood pressure treatment. After characterizing the properties of the (nano)materials and their formulations, we assessed their effects in vitro against three fungal species: Coniophora puteana, Gloeophyllum trabeum, and Trametes versicolor, finding them to be mediated only partially by ionic transformation. To assess the use phase, we quantify both release rate and form. Cu leaching rates for the two types of impregnated wood (conventional and nanoenabled) are not significantly different at 172 ± 6 mg/m2, with Cu being released predominantly in ionic form. Various simulations of outdoor aging with release sampling by runoff, during condensation, by different levels of mechanical shear, all resulted in comparable form and rate of release from the nanoenabled or the molecular impregnated woods. Because of dissolving transformations, the nanoenabled impregnation does not introduce additional concern over and above that associated with the traditional impregnation. In contrast, Cu released from wood coated with the CuO acrylate contained particles, but the rate was at least 100-fold lower. In the same ranking, the effectiveness to protect against the wood-decaying basidiomycete Coniophora puteana was significant with both impregnation technologies but remained insignificant for untreated wood and wood coated by the acrylic CuO. Accordingly, a lifecycle-based sustainability analysis indicates that the CuO acrylic coating is less sustainable than the technological alternatives, and should not be developed into a commercial product.

  • Using Silica Coated Nanoscale Zerovalent Particles for the Reduction of Chlorinated Ethylenes

    Lenka Honetschlgerov, Petra Janoukovcov, Milica Velimirovic, Martin Kubal, Leen Bastiaens
    2018 - Silicon, 6: 2593-2601

    Abstract: 

    The impact of a silica coating on the degradation potential of nanoscale zerovalent iron (nZVI) particles toward a mixture of chlorinated ethylenes is presented. The newly employed stabilization method for nZVI, based on silica deposition from saturated sodium silicate water glass, produces nZVI particles with a similar reactivity as non-stabilized particles. Moreover the removal rate constant kM of trichloroethylene (0.1740 L g−1 d−1 Fe0) and cis-dichloroethylene (0.1045 L g−1 d−1Fe0) was significantly improved (almost by a factor of 2) for stabilized nZVI. X-ray photoelectron spectroscopy (XPS) and Wavelength Dispersive X-ray Fluorescence (WDXRF) analyzes revealed a high durability of silica coating and the coating left at least half of nZVI surface silica free for reaction for more than 5 weeks. The silica coating did not affect the surface composition of silica coated nZVI which was confirmed by the very similar distribution of degradation products and corrosion products (Fe3O4, FeOOH) as was found for non-coated nanoparticles. An enhanced reactivity supplemented with a stable corrosion properties indicates that silica coated nZVI has potential as an efficient remediation agent toward chlorinated ethylenes.

  • Where is the nano? Analytical approaches for the detection and quantification of TiO2 engineered nanoparticles in surface waters

    Andreas Gondikas, Frank von der Kammer, Ralf Kaegi, Olga Borovinskaya, Elisabeth Neubauer, Jana Navratilova, Antonia Praetorius, Geert Cornelis, Thilo Hofmann
    2018 - Environmental Science: Nano, 2: 313-326

    Abstract: 

    Detecting and quantifying engineered nanoparticles (ENPs) in complex environmental matrices requires the distinction between natural nanoparticles (NNPs) and ENPs. The distinction of NNPs and ENPs for regulatory purposes calls for cost-efficient methods, but is hampered by similarities in intrinsic properties, such as particle composition, size, density, surface chemistry, etc. Titanium dioxide (TiO2) ENPs, for instance, are produced in very large quantities but Ti also commonly occurs naturally in nano-scale minerals. In this work, we focus on utilizing particle size and composition to identify ENPs in a system with a significant background concentration of the target metal. We have followed independent approaches involving both conventional and state-of-the-art analytical techniques to detect and quantify TiO2 ENPs released into surface waters from sunscreen products and to distinguish them from Ti-bearing NNPs. To achieve this, we applied single particle inductively coupled plasma mass spectrometry with single-element (spICPMS) and multi-element detection (time-of-flight) spICP-TOFMS, together with transmission electron microscopy (TEM), automated scanning electron microscopy (autoSEM), and bulk elemental analyses. A background concentration of Ti-bearing NPs (approximately 5 × 10particles per ml), possibly of natural origin, was consistently observed outside the bathing season. This concentration increased by up to 40% during the bathing season. Multi-element analysis of individual particles using spICP-TOFMS revealed that Al, Fe, Mn, and Pb are often present in natural Ti-bearing NPs, but no specific multi-element signatures were detected for ENPs. Our data suggests that TiO2 ENPs enter the lake water during bathing activities, eventually agglomerating and sedimenting. We found adhesion of the TiO2 ENPs to the air–water interface for short time periods, depending on wind conditions. This study demonstrates that the use of spICP-TOFMS and spICPMS in combination with other conventional analytical techniques offers significant advantages for discriminating between NNPs and ENPs. The quantitative data produced in this work can be used as input for modeling studies or as a benchmark for analysis protocols and model validations.

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