Publications

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Publications in peer reviewed journals

7 Publications found
  • A versatile test system to determine nanomaterial heteroagglomeration attachment efficiency

    Helene Walch, Nada Bašić, Antonia Praetorius, Frank von der Kammer, Thilo Hofmann
    2024 - Environmental Science: Nano, 11: 588-600

    Abstract: 

    Engineered and incidental nanomaterials are emerging contaminants of environmental concern. In aquatic systems, their transport, fate, and bioavailability strongly depend on heteroagglomeration with natural suspended particulate matter (SPM). Since particulate contaminants underlie different mechanisms than dissolved contaminants, harmonized, particle-specific test systems and protocols are needed for environmental risk assessment and for the comparability of environmental fate studies. The heteroagglomeration attachment efficiency (α_het) can parametrize heteroagglomeration in fate models which inform exposure assessment. It describes the attachment probability upon nanomaterial-SPM collision and reflects the physicochemical affinity between their surfaces. This work introduces a new versatile test system to determine α_het under environmentally relevant conditions. The test matrix combines model SPM analogs and an adjustable model hydrochemistry, both designed to represent the process-relevant characteristics of natural freshwater systems, while being standardizable and reproducible. We developed a stirred-batch method that addresses shortcomings of existing strategies for α_het determination and conducted heteroagglomeration experiments with CeO2 (<25 nm) as a model nanomaterial. Single-particle ICP-MS allowed working at environmentally relevant concentrations and determination of α_het values by following the decrease of non-reacted nanomaterial over time. The α_het values received for the model freshwater test matrix were evaluated against a natural river-water sample. Almost identical α_het values show that the model test system adequately reflects the natural system, and the experimental setup proved to be robust and in line with the theoretical concept for α_het determination. Combinations of natural SPM in model water and model SPM in natural water allowed further insight into their respective impacts. The α_het values determined for nano-CeO2 in the natural river water sample (0.0044-0.0051) translate to a travel distance of 143-373 km downstream until 50% is heteroagglomerated, assuming an average flow velocity of 5 km h-1 and an SPM concentration of 20-45 mg L-1. These half-lives illustrate the importance of heteroagglomeration kinetics.

  • An integrated approach to testing and assessment (IATA) to support grouping and read-across of nanomaterials in aquatic systems

    Richard K. Cross, Dave Spurgeon, Claus Svendsen, Elma Lahive, Simon Little, Frank von der Kammer, Frédéric Loosli, Marianne Matzke, Teresa F. Fernandes, Vicki Stone, Willie J.G.M. Peijnenburg, Eric A.J. Bleeker
    2024 - Nano Today, 54: 102065

    Abstract: 

    Even small changes in physicochemical properties of nanoforms (NFs), can drive differences in their environmental fate and hazard. The large number of new materials being developed means it will not be feasible to test and characterise the fate, behaviour and (eco)toxicity of each individual NF. This is further amplified by transformations of NFs over their lifecycle, changing the processes governing their risk. A common complexity arises from dissolution, where the combined toxicity of the exposure arises from both the solutes and any remaining particles contribution to the overall toxicity of the exposure. For efficient and effective risk assessment, it is the most relevant form of the NF for a given exposure that should be targeted for testing and assessment. In aquatic systems, functional fate processes (including dissolution, dispersion stability and chemical and biological transformations) determine the NF’s exposure relevant form. Whilst transformations in the environment alter the initial properties of an NF, different NFs may follow a shared functional fate pathway and ultimately present a similar fate and hazard profile in the environment. Therefore, these processes may be used to scientifically justify grouping NFs and read-across for specific endpoints from data rich NF(s) to verified members of the group that have not been tested yet. Integrated Approaches to Testing and Assessment (IATA) have been used in other regulatory contexts to support the collection and integration of relevant existing information as well as the targeted generation of new data to support grouping and read-across. Here, a new IATA is presented consisting of decision nodes focused on dissolution, dispersion stability, chemical transformations and the relative contribution to toxicity of the particle and dissolved component of the overall exposure. The IATA focuses on the fate of NFs in aquatic systems outside of the body, but it can be considered a template for future assessment of in vivo kinetics, which will require further development. Guidance on tiered testing approaches and thresholds for grouping within each decision node are critically discussed. Worked examples for ecotoxicity of metal oxide NFs in aqueous systems (in microbial communities isolated from soils and for lettuce plants in hydroponic systems) demonstrate successful identification of the exposure relevant form of the NF in these case studies and allows for different grouping of NFs through application of the IATA.

  • Hydrolysis of Antimicrobial Peptides by Extracellular Peptidases in Wastewater

    Natalie Wichmann, Richard Gruseck, Michael Zumstein
    2024 - Environ. Sci. Technol., 1: 717–726

    Abstract: 

    Several antimicrobial peptides (AMPs) are emerging as promising novel antibiotics. When released into wastewater streams after use, AMPs might be hydrolyzed and inactivated by wastewater peptidases─resulting in a reduced release of active antimicrobials into wastewater-receiving environments. A key step towards a better understanding of the fate of AMPs in wastewater systems is to investigate the activity and specificity of wastewater peptidases. Here, we quantified peptidase activity in extracellular extracts from different stages throughout the wastewater treatment process. For all four tested municipal wastewater treatment plants, we detected highest activity in raw wastewater. Complementarily, we assessed the potential of enzymes in raw wastewater extracts to biotransform 10 selected AMPs. We found large variations in the susceptibility of AMPs to enzymatic transformation, indicating substantial substrate specificity of extracted enzymes. To obtain insights into peptidase specificities, we searched for hydrolysis products of rapidly biotransformed AMPs and quantified selected products using synthetic standards. We found that hydrolysis occurred at specific sites and that these sites were remarkably conserved across the four tested wastewaters. Together, these findings provide insights into the fate of AMPs in wastewater systems and can inform the selection and design of peptide-based antibiotics that are hydrolyzable by wastewater peptidases.

  • Impact of Heavy Metals (Cu, Fe, Pb, Zn) on Carbon and Nitrogen Uptake of the Diatom-Bearing Benthic Foraminifera Heterostegina Depressa

    Mario Bubl, Petra Heinz, Wolfgang Wanek, Michael Schagerl, Thilo Hofmann, Michael Lintner
    2024 - Heliyon, 10: in press

    Abstract: 

    Foraminifera are protists primarily living in benthic marine and estuarine environments. We studied uptake of inorganic carbon (C) and nitrogen (N) of the photosymbiont-bearing benthic coral reef foraminifera Heterostegina depressa in the presence of heavy metals.
    Incubation experiments were accomplished with artificial seawater enriched with copper, iron, lead and zinc at two different concentration levels (10 and 100 fold enriched in contrast to the usual culture medium). Additionally, isotopically labelled 13C-sodium bicarbonate and 15N-ammonium chloride were added to trace their assimilation over time (1 d, 3 d, 5 d, 7 d). Pulse-amplified modulated fluorescence measurements were performed to measure the potential impacts of heavy metals on chlorophyll fluorescence of the photosymbiont. Increased levels of copper (430.5 μg Cu/l) exhibited the greatest toxicity, while for low levels no effect on the overall metabolism of the foraminifera and the fluorescence activity of the photosymbiont could be detected. Iron (III) increased the symbiont activity, independent of concentration applied (44.5 and 513.3 μg Fe/l), which indicates Fe-limitation of the algal symbiont. Lead enrichment showed no detectable effect even at high concentration. Low concentrations of zinc (35.1 μg Zn/l) promoted the metabolism of the foraminifera, while high concentrations (598.4 μg Zn/l) were toxic. At low levels, two metals (Fe and Zn) promoted symbiont activity, at high levels, iron still boosted photosynthesis, but Zn and Cu had a negative impact on the obligatory photosynthetic symbionts.
  • Influence of plastic shape on interim fragmentation of compostable materials during composting

    Patrizia Pfohl, Markus Rueckel, Lars Meyer, Glauco Battagliarin, Andreas Künkel, Thorsten Hüffer, Michael Zumstein, Thilo Hofmann, Wendel Wohlleben
    2024 - Microplastics and Nanoplastics, 4: in press

    Abstract: 

    Common experience with rotting wooden buildings demonstrates that fragmentation is a necessary natural process during biodegradation. In analogy, the loss of structural integrity of biodegradable plastics during biodegradation produces interim microplastic fragments. It is currently not known which parameters govern fragmentation kinetics: chemical structure, physical shape, and composite layers, or composting conditions may all be relevant. Here we investigated the influence of physical shape on the fragmentation of a polyester blend during laboratory tests simulating industrial composting. Methods previously validated on micronized granules as model shape were applied to shapes that better represent consumer products, such as micronized thin films and shredded plastic-coated paper cups. The peak interim number of detected fragments, which are between 3 and 2000 µm, ranked highest for micronized films, lower for micronized plastic granules, and even lower for coated paper cups. The layered structure of polyester on cellulose may thus have stabilized the biodegrading polyester compound against fragmentation. For thin films, fragment counts dissipated with halftime of 2.5 days, and less than 10–8% of the initially added polyester mass was detected in fragments between 3 and 25 µm at the last sampling time point. The physical shape and multilayer structure of the polymer-containing product were found to be decisive for fragmentation kinetics, indicating that tests on micronized polymer granules might not be representative of the release mechanism of fragments from consumer products containing plastic coatings.

  • The efficacy of Pb, As(V) and Sb(III ) removal by biochar is determined by solution chemistry

    Sampriti Chaudhuri, Gabriel Sigmund, Naresh Kumar, Thorsten Hüffer, Andreas Mautner, Thilo Hofmann
    2024 - Environmental Science: Water Research & Technology, in press

    Abstract: 

    Biochars (BC) are cost-effective and sustainable sorbents to clean up waters polluted with metal(loid)s. Understanding the influence of water chemistry is critical in identifying processes that limit metal(loid) removal. To address this, we investigated the removal of lead [Pb], arsenate [As(V)], and antimonite [Sb(III)] using BC in the presence of various solution constituents. A design of experiments approach was used to investigate sorption for each metal(loid)-BC setup (Pb with a straw BC, As(V) with charred wood-dolomite and Sb(III) with a steam-activated wood BC) with twenty-five different background solutions varying in calcium (Ca), natural organic matter (NOM), phosphorus (P), and iron [Fe(III)] content. Background solution composition affected removal of Pb (29 to 100%) more strongly than that of As(V) (37 to 92%) and Sb(III) (20 to 70%), with the selected BC at the metal(loid) concentrations studied. Pb removal was associated with Fe(III)–NOM–Ca organo-mineral phases for solutions containing Fe(III), NOM and Ca. As(V) sorption was enhanced by Ca due to cation-bridging and reducing the competition for sorption sites by NOM and P in high NOM and/or P containing solutions. Sb(III) sorption was hindered by oxidation to Sb(V) through redox active moieties in the BC in all solutions. Sb(III) removal decreased in the presence of high Fe(III), because Fe(III)/Fe(III)–NOM phases blocked accessibility to sorption sites in the highly porous BC, and/or due to enhanced oxidation of Sb(III) to the more mobile (but less toxic) Sb(V). Ideally, the design of BC sorbents for the removal of metal(loid)s from contaminated waters should a priori consider complex solution compositions.

  • Tire Materials Disturb Transformations of Nitrogen Compounds and Affect the Structure of Biomass in Aerobic Granular Sludge Reactors

    Piotr Jachimowicz, Ruoting Peng, Thorsten Hüffer, Thilo Hofmann, Agnieszka Cydzik-Kwiatkowska
    2024 - Journal of Hazardous Materials, 465: 133223

    Abstract: 

    Tire materials (TMs) present a notable hazard due to their potential to release harmful chemicals and microplastics into the environment. They can infiltrate wastewater treatment plants, where their effects remain inadequately understood, raising concerns regarding their influence on treatment procedures. Thus, this study investigated the impact of TMs in wastewater (10, 25, 50 mg/L) on wastewater treatment efficiency, biomass morphology, and microbial composition in aerobic granular sludge (AGS) reactors. TM dosage negatively correlated with nitrification and denitrification efficiencies, reducing overall nitrogen removal, but did not affect the efficiency of chemical-oxygen-demand removal. The presence of TMs increased the diameter of the granules due to TM incorporation into the biomass. The most frequently leached additives from TMs were N-(1,3-dimethylbutyl)-N′-phenyl-1,4-phenylenediamine, benzothiazole (BTH), and 2-hydroxybenzothiazole. In the treated wastewater, only BTH and aniline were detected in higher concentrations, which indicates that tire additives were biodegraded by AGS. The microbial community within the AGS adapted to TMs and their chemicals, highlighting the potential for efficient degradation of tire additives by bacteria belonging to the genera Rubrivivax, Ferruginibacter, and Xanthomonas. Additionally, our research underscores AGS's ability to incorporate TMs into biomass and effectively biodegrade tire additives, offering a promising solution for addressing environmental concerns related to TMs.

Book chapters and other publications

1 Publication found
  • Polymer Biodegradability 2.0: A Holistic View on Polymer Biodegradation in Natural and Engineered Environments

    Michael Sander, Miriam Weber, Christian Lott, Michael Zumstein, Andreas Künkel, Glauco Battagliarin
    2024 - 65-110. in Advances in Polymer Science. Springer International Publishing

    Abstract: 

    Biodegradable polymers are an important part of the solution toolbox to achieve circularity in the plastic economy and overcome negative impacts of a linear plastic economy. Biodegradable polymers need to excel not only on a mechanical performance level in the application to fulfill their function during the use phase but also on a biodegradation performance level after use. The biodegradation performance is tailored to the application and the receiving environment of the polymer product after use, which can be both engineered systems (e.g., compost, anaerobic digestors, wastewater treatment plants) and natural systems (e.g., soils, freshwater, or marine environments). This chapter addresses key aspects of polymer biodegradability and biodegradation in both natural and engineered systems with the goal to advance a more holistic view on the topic and, thereby, provide guidance for all stakeholders working on developing, testing, and regulating biodegradable polymers. These aspects include definitions of biodegradability and biodegradation, elucidating polymer- and environmental factors that control the biodegradation process, a discussion of the analytical chemistry of polymer biodegradation, polymer biodegradability testing and certification, as well as a brief overview of research needs. In accordance with the diverse backgrounds of the authors of the chapter, this chapter targets all stakeholder groups from academics to industry and regulators.