Publications

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Publications in peer reviewed journals

18 Publications found
  • A critical evaluation of short columns for estimating the attachment efficiency of engineered nanomaterials in natural soils

    Knapp Karin Norrfors, Vesna Micić, Olga Borovinskaya, Frank von der Kammer, Thilo Hofmann, Geert Cornelis
    2021 - Environmental Science: Nano, 8: 1801-1814

    Abstract: 

    Short, saturated packed columns are used frequently to estimate the attachment efficiency (α) of engineered nanomaterials (ENMs) in relatively homogeneous porous media, but a combined experimental and theoretical approach to obtain α-values for heterogeneous natural soils has not yet been agreed upon. Accurately determined α-values that can be used to study and predict ENM transport in natural soils should vary with ENM and soil properties, but not with experimental settings. We investigated the effect of experimental conditions, and used different methods to obtain soil parameters, essential to calculate α. We applied 150 different approaches onto 52 transport experiments using short columns with 5 different natural soils and 20 and 80 nm gold- or 27 nm silver sulphide ENMs. The choice of column end-filter material and pore size appeared critical to avoid overestimating α owing to filter – ENM interactions and/or incomplete saturation of the column. Using a low ionic strength (4.4 x 10-5 mol L-1) artificial rain water as an aqueous medium avoided ENM homo- or heteroaggregation in all soils, as confirmed by single-particle inductively coupled plasma - time of flight mass spectrometry. ENM breakthrough curves could be modelled using colloid filtration theory assuming irreversible attachment only. α-values calculated from this model, having the grain size represented by a single average size, accounting for dispersivity and effective porosity based on a prior inert tracer test, explained up to 42 % of the variance in α as revealed by partial least squares analysis. However, column length and dispersivity remained as important experimental parameters, which calls for further standardisation efforts of column tests with ENMs in natural soils, preferably cross-validated with batch tests.

  • Additives and polymer composition influence the interaction of microplastics with xenobiotics

    Darius Hummel, Andreas Fath, Thilo Hofmann, Thorsten Hüffer
    2021 - Environmental Chemistry, 18: 201-110

    Abstract: 

    Microplastics are particulate contaminants of global concern. Interactions of microplastics with organic

    contaminants are frequently studied with commercially available polymer materials as surrogates. The influence of the

    polymer structure (i.e. internal 3D polymer geometry and monomer chain length) and the presence of additives on their

    interactions with xenobiotics remains unclear. This work investigates sorption of three sorbates of environmental concern

    to two polyamide (PA) and two polyvinyl chloride (PVC) sorbents of different molecular composition and additive

    content, respectively. Sorption was studied using complementary data from sorption isotherms and confocal laser-

    scanning microscopy. The additives in PVC increased sorption affinity owing to an increased sorbent hydrophobicity and a

    higher void volume within the polymer. Surface area normalisation indicated surface adsorption for unplasticised PVC and

    absorption for 1,2-cyclohexane dicarboxylic acid diisononyl ester (DINCH)-plasticised PVC, which were confirmed using

    confocal laser-scanning microscopy. The strong sorption to PA was mainly driven by hydrogen-bond interactions. The

    contribution depended on the molecular features of the sorbent and the sorbate. Confocal laser-scanning microscopy

    showed that PA6 was taking up more sorbate into its bulk polymer matrix than PA12, the two being different in their

    chemical composition. This difference could be attributed to the higher swelling capability of PA6. The results emphasise

    that the molecular structure of the polymer and the presence of additives have to be taken into consideration when sorption

    of organic substances to plastics is investigated.

  • Biotechnological synthesis of Pd/Ag and Pd/Au nanoparticles for enhanced Suzuki-Miyaura cross-coupling activity

    Richard Kimber, Fabio Parmeggiani, Thomas Neill, Mohamed Merroun, Gregory Goodlet, Nigel Powell, Nicholas Turner, Jonathan Lloyd
    2021 - Microbial Biotechnology, 14: 2435-2447

    Abstract: 

    Bimetallic nanoparticle catalysts have attracted considerable attention due to their unique chemical and physical properties. The ability of metal-reducing bacteria to produce highly catalytically active monometallic nanoparticles is well known; however, the properties and catalytic activity of bimetallic nanoparticles synthesized with these organisms is not well understood. Here, we report the one-pot biosynthesis of Pd/Ag (bio-Pd/Ag) and Pd/Au (bio-Pd/Au) nanoparticles using the metal-reducing bacterium, Shewanella oneidensis, under mild conditions. Energy dispersive X-ray analyses performed using scanning transmission electron microscopy (STEM) revealed the presence of both metals (Pd/Ag or Pd/Au) in the biosynthesized nanoparticles. X-ray absorption near-edge spectroscopy (XANES) suggested a significant contribution from Pd(0) and Pd(II) in both bio-Pd/Ag and bio-Pd/Au, with Ag and Au existing predominately as their metallic forms. Extended X-ray absorption fine-structure spectroscopy (EXAFS) supported the presence of multiple Pd species in bio-Pd/Ag and bio-Pd/Au, as inferred from Pd-Pd, Pd-O and Pd-S shells. Both bio-Pd/Ag and bio-Pd/Au demonstrated greatly enhanced catalytic activity towards Suzuki-Miyaura cross-coupling compared to a monometallic Pd catalyst, with bio-Pd/Ag significantly outperforming the others. The catalysts were very versatile, tolerating a wide range of substituents. This work demonstrates a green synthesis method for novel bimetallic nanoparticles that display significantly enhanced catalytic activity compared to their monometallic counterparts.

  • Catalytic effects of photogenerated Fe(II) on the ligand-controlled dissolution of Iron(hydr)oxides by EDTA and DFOB

    Jagannath Biswakarma, KyounglimKang, Walter D.C.Schenkeveld, Stephan M. Kraemer, Janet G.Hering. Stephan J.Hug
    2021 - Chemosphere, 263: 128188

    Abstract: 

    Low bioavailability of iron due to poor solubility of iron(hydr)oxides limits the growth of microorganisms and plants in soils and aquatic environments. Previous studies described accelerated dissolution of iron(hydr)oxides under continuous illumination, but did not distinguish between photoreductive dissolution and non-reductive processes in which photogenerated Fe(II) catalyzes ligand-controlled dissolution. Here we show that short illuminations (5–15 min) accelerate the dissolution of iron(hydr)oxides by ligands during subsequent dark periods under anoxic conditions. Suspensions of lepidocrocite (Lp) and goethite (Gt) (1.13 mM) with 50 μM EDTA or DFOB were illuminated with UV-A light of comparable intensity to sunlight (pH 7.0, bicarbonate-CO2 buffered solutions). During illumination, the rate of Fe(II) production was highest with Gt-EDTA; followed by Lp-EDTA > Lp-DFOB > Lp > Gt-DFOB > Gt. Under anoxic conditions, photochemically produced Fe(II) increased dissolution rates during subsequent dark periods by factors of 10–40 and dissolved Fe(III) reached 50 μM with DFOB and EDTA. Under oxic conditions, dissolution rates increased by factors of 3–5 only during illumination. With DFOB dissolved Fe(III) reached 35 μM after 10 h of illumination, while with EDTA it peaked at 15 μM and then decreased to below 2 μM. The observations are explained and discussed based on a kinetic model. The results suggest that in anoxic bottom water of ponds and lakes, or in microenvironments of algal blooms, short illuminations can dramatically increase the bioavailability of iron by Fe(II)-catalyzed ligand-controlled dissolution. In oxic environments, photostable ligands such as DFOB can maintain Fe(III) in solution during extended illumination.

  • Effects of heavy elements (Pb, Cu, Zn) on algal food uptake by Elphidium excavatum (Foraminifera)

    Michael Lintner, Bianca Lintner, Wolfgang Wanek, Nina Keul, Frank von der Kammer, Thilo Hofmann, Petra Heinz
    2021 - Heliyon, 7: 08427

    Abstract: 

    Foraminifera are unicellular organisms and play a pivotal role in the marine material cycles. Past observations have shown that the species Elphidium excavatum is the most common foraminifera in the Baltic Sea. Feeding experiments showed that the food uptake and thus the turnover of organic matter are influenced by changes of physical parameters (e.g., temperature, salinity). Since many areas of the Baltic Sea are strongly affected by anthropogenic activity and are strongly contaminated by heavy elements from shipping in the past, this study examined the effect of heavy elements pollution on the food uptake of the most common foraminiferal species of the Baltic Sea, E. excavatum which was a subject of several previous studies. Therefore, Baltic Sea seawater was enriched with metals at various levels above normal seawater levels and the uptake of 13C- and 15N-labelled phytodetritus was measured by isotope ratio mass spectrometry. For each combination of metal type, concentration and time point 20 individuals of E. excavatum (three replicates) were fed with the green algae Dunaliella tertiolecta. The effect of dose parameters was measured in a two-way analysis of variance. Significant differences of food uptake were observable at different types and levels of heavy elements in sea water. Even a 557-fold increase in the Pb concentration did not affect food uptake, whereas strong negative effects were found for higher levels of Zn (144 and 1044-fold) and especially for Cu (5.6 and 24.3-fold). In summary it can be stated, that an increase in the heavy elements pollution in the Kiel Fjord will lead to a significant reduction in the turnover of organic matter by foraminifera such as E. excavatum.

  • Environmentally persistent free radicals are ubiquitous in wildfire charcoals and remain stable for years

    Gabriel Sigmund, Cristina Santín, Marc Pignitter, Nathalie Tepe, Stefan H. Doerr, Thilo Hofmann
    2021 - Communications Earth & Environment, 2: 68

    Abstract: 

    Globally landscape fires produce about 256 Tg of pyrogenic carbon or charcoal each year. The role of charcoal as a source of environmentally persistent free radicals, which are precursors of potentially harmful reactive oxygen species, is poorly constrained. Here, we analyse 60 charcoal samples collected from 10 wildfires, that include crown as well as surface fires in forest, shrubland and grassland spanning different boreal, temperate, subtropical and tropical climate. Using electron spin resonance spectroscopy, we measure high concentrations of environmentally persistent free radicals in charcoal samples, much higher than those found in soils. Concentrations increased with degree of carbonization and woody fuels favoured higher concentrations. Moreover, environmentally persistent free radicals remained stable for an unexpectedly long time of at least 5 years. We suggest that wildfire charcoal is an important global source of environmentally persistent free radicals, and therefore potentially of harmful reactive oxygen species.

  • Genomic insights into diverse bacterial taxa that degrade extracellular DNA in marine sediments

    Kenneth Wasmund, Claus Pelikan, Arno Schintlmeister, Michael Wagner, Margarete Watzka, Andreas Richter, Srijak Bhatnagar, Amy Noel, Casey R J Hubert, Thomas Rattei, Thilo Hofmann, Bela Hausmann, Craig W Herbold, Alexander Loy
    2021 - Nature MIcrobiology, 6: 885-898

    Abstract: 

    Extracellular DNA is a major macromolecule in global element cycles, and is a particularly crucial phosphorus, nitrogen and carbon source for microorganisms in the seafloor. Nevertheless, the identities, ecophysiology and genetic features of DNA-foraging microorganisms in marine sediments are largely unknown. Here, we combined microcosm experiments, DNA stable isotope probing (SIP), single-cell SIP using nano-scale secondary isotope mass spectrometry (NanoSIMS) and genome-centric metagenomics to study microbial catabolism of DNA and its subcomponents in marine sediments. 13C-DNA added to sediment microcosms was largely degraded within 10 d and mineralized to 13CO2. SIP probing of DNA revealed diverse ‘Candidatus Izemoplasma’, Lutibacter, Shewanella and Fusibacteraceae incorporated DNA-derived 13C-carbon. NanoSIMS confirmed incorporation of 13C into individual bacterial cells of Fusibacteraceae sorted from microcosms. Genomes of the 13C-labelled taxa all encoded enzymatic repertoires for catabolism of DNA or subcomponents of DNA. Comparative genomics indicated that diverse ‘Candidatus Izemoplasmatales’ (former Tenericutes) are exceptional because they encode multiple (up to five) predicted extracellular nucleases and are probably specialized DNA-degraders. Analyses of additional sediment metagenomes revealed extracellular nuclease genes are prevalent among Bacteroidota at diverse sites. Together, our results reveal the identities and functional properties of microorganisms that may contribute to the key ecosystem function of degrading and recycling DNA in the seabed.

  • Methanol-based extraction protocol for insoluble and moderately water-soluble nanoparticles in plants to enable characterization by single particle ICP-MS

    Stephanie Laughton, Adam Laycock, Garret Bland, Frank von der Kammer, Thilo Hofmann, Elizabeth A. Casman, Gregory V. Lowry
    2021 - Analytical and Bioanalytical Chemistry, 413: 299–314

    Abstract: 

    The detection and characterization of soluble metal nanoparticles in plant tissues are an analytical challenge, though a scientific necessity for regulating nano-enabled agrichemicals. The efficacy of two extraction methods to prepare plant samples for analysis by single particle ICP-MS, an analytical method enabling both size determination and quantification of nanoparticles (NP), was assessed. A standard enzyme-based extraction was compared to a newly developed methanol-based approach. Au, CuO, and ZnO NPs were extracted from three different plant leaf materials (lettuce, corn, and kale) selected for their agricultural relevance and differing characteristics. The enzyme-based approach was found to be unsuitable because of changes in the recovered NP size distribution of CuO NP. The MeOH-based extraction allowed reproducible extraction of the particle size distribution (PSD) without major alteration caused by the extraction. The type of leaf tissue did not significantly affect the recovered PSD. Total metal losses during the extraction process were largely due to the filtration step prior to analysis by spICP-MS, though this did not significantly affect PSD recovery. The methanol extraction worked with the three different NPs and plants tested and is suitable for studying the fate of labile metal-based nano-enabled agrichemicals.

  • Microplastic extraction protocols can impact the polymer structure

    Patrizia Pfohl, Christian Roth, Lars Meyer, Ute Heinemeyer, Till Gruendling, Christiane Lang, Nikolaus Nestle, Thilo Hofmann, Wendel Wohlleben, Sarah Jessl
    2021 - Microplastics and Nanoplastics, 1: 8

    Abstract: 

    Although microplastics are ubiquitous in today’s natural environments, our understanding of the materials, quantities, and particle sizes involved remains limited. The recovery of microplastics from different types of environmental matrices requires standardized matrix digestion protocols that allow inter-laboratory comparisons and that have no effect on the polymers themselves. A number of commonly used digestion methods rely on oxidation with concentrated hydrogen peroxide solutions to remove organic matter from the matrix. However, this can alter the nature of polymers through hydrolysis and often does not lead to a complete matrix removal. We have therefore investigated the use of two altered matrix digestion protocols, an acidic (Fenton) protocol and a new alkaline (Basic Piranha) protocol, focusing mainly on the effect on biodegradable polymers (polylactide, polybutylene adipate terephthalate, polybutylene succinate) and polymers with known degradation pathways via hydrolysis (thermoplastic polyurethanes, polyamide). Comparing the initial surface textures, chemical compositions, and particle size distributions with those obtained after digestion revealed that the Fenton protocol left most of the polymers unchanged. The ferrous residue that remains following Fenton digestion had no effect on either the polymer composition or the particle size distribution, but could disturb further analytics (e.g. Raman microscopy due to auto-fluorescence). While increasing the chance of complete matrix removal, the more powerful Basic Piranha protocol is also more likely to affect the polymer properties: Polylactide polymers in particular showed signs of degradation under alkaline digestion (reduced polylactide content, holes in the polymer matrix), indicating the unsuitability of the Basic Piranha protocol in this specific case. Polyamide, however, remained stable during the Basic Piranha treatment, and the surface chemistry, the particle size as well as the molar mass distribution of the investigated thermoplastic polyurethanes were also not affected. Hence, this protocol offers a powerful alternative for microplastic analysis with focus on particle size in more complex environmental matrices (e.g. removal of cellulose in soil), while avoiding ferrous Fenton residue. Unexpectedly, also tire rubber, a frequent target analyte in microplastic monitoring, was found to be susceptible to artefact structures by both oxidation protocols. In summary, controls for the specific combination of polymer and sample preparation protocol are highly recommended to select the most fitting protocol. Here selected suitable combinations are reported.

  • Microplastics and nanoplastics barely enhance contaminant mobility in agricultural soils

    Stephanie Castan, Charlotte Henkel, Thorsten Hüffer, Thilo Hofmann
    2021 - Communications Earth & Environment, 193: 1-9

    Abstract: 

    Farmland soils are prone to contamination with micro- and nanoplastics through a variety of agricultural practices. Concerns are recurrently raised that micro- and nanoplastics act as vector for organic contaminants to deeper soil layers and endanger groundwater resources. Whether and to what extent micro- and nanoplastics facilitate the transport of organic contaminants in soil remains unclear. Here we calculated the ratio between transport and desorption time scales using two diffusion models for micro- and nanoplastics between 100 nm and 1 mm. To identify micro- and nanoplastics bound contaminant transport we evaluated diffusion and partitioning coefficients of prominent agrochemicals and additives and of frequently used polymers e.g., polyethylene and tire material. Our findings suggest that the desorption of most organic contaminants is too fast for micro- and nanoplastics to act as transport facilitators in soil. Contaminant transport enabled by microplastics was found to be relevant only for very hydrophobic contaminants (logKow >5) under preferential flow conditions. While micro- and nanoplastics might be a source of potentially harmful contaminants in farmland soils this study suggests that they do not considerably enhance contaminant mobility.

  • New guidance brings clarity to environmental hazard and behaviour testing of nanomaterials

    Elijah Joel Petersen, Greg Gerard Goss, Frank von der Kammer, Alan James Kennedy
    2021 - Nature Nanotechnology, 16: 482–483
  • Novel multimethod approach for the determination of the colloidal stability of nanomaterials in complex environmental mixtures using a global stability index: TiO2 as case study

    Elena Badetti, Andrea Brunelli, Gianpietro Basei, Julián Alberto Gallego-Urrea, Serge Stoll, Helene Walch, Antonia Praetorius, Frank von der Kammer, Antonio Marcomini
    2021 - Science of The Total Environment, 801: 149607

    Abstract: 

    A systematic study on the colloidal behavior of uncoated and polyvinylpyrrolidone (PVP) coated TiO2 engineered nanomaterials (ENMs) in simulated aqueous media is herein reported, in which conditions representative for natural waters (pH, presence of divalent electrolytes (i.e. Ca2+/Mg2+ and SO42−), of natural organic matter (NOM) and of suspended particulate matter (SPM)) were systematically varied. The colloidal stability of the different dispersions was investigated by means of Dynamic and Electrophoretic Light Scattering (DLS and ELS) and Centrifugal Separation Analysis (CSA), and a global stability index based on these three techniques was developed. The index allows to quantitatively classify the nano-based dispersions according to their colloidal stability affected by the different parameters studied. This multimethod approach clearly identifies inorganic SPM followed by divalent electrolytes as the main natural components destabilizing TiO2 ENMs upon entering in simulated natural waters, while it highlights a moderate stabilization induced by NOM, depending mainly on pH. Moreover, the PVP coating was found to attenuate the influence of these parameters on the colloidal stability. The obtained results show how the global stability index developed is influenced by the complexity of the system, suggesting the importance of combining the information gathered from all the techniques employed to better elucidate the fate and behavior of ENMs in natural surface waters.

  • PAHs sorption to biochar colloids changes their mobility over time

    Yang Wen, Qu Ting, Flury Markus, Zhang Xin, Gabriel Sigmund, Shang Jianying, Li Baoguo
    2021 - Journal of Hydrology, 603: in press

    Abstract: 

    Biochar is an efficient sorbent for polycyclic aromatic hydrocarbons (PAHs). However, little is known about PAHs sorption kinetics and the effect on the mobility of biochar colloids in saturated porous media. In this study, naphthalene (NAP) and phenanthrene (PHE) were chosen as typical PAHs. In different stages, different sorption sites of PAHs on biochar played a distinct role in affecting the transport of biochar colloids in saturated porous media. The biochar colloids showed less negative surface charge as the contact time between biochar colloids and PAHs increased from 0.017 h to 96 h, which led to the mobility of biochar colloids decreasing over time. But after 168 h contact time, the surface charge of biochar colloids became more negative again, and the inhibition effect of PAHs on biochar colloid transport was weakened. This was related to the sorption kinetics of PAHs on biochar colloids: (1) PAHs sorption onto outer biochar surface; and (2) adsorbed PAHs diffusion into internal biochar pores. PAHs sorption onto the outer biochar surface shielded the negative surface charge and then decreased the mobility of biochar colloids, and then the adsorbed PAHs diffusion into internal biochar pores increased their mobility again. Our results suggested that porous colloids-facilitated PAHs transport in porous media might be highly related to interaction time between PAHs and porous colloids.

  • Sulfidated nano-scale zerovalent iron is able to effectively reduce in situ hexavalent chromium in a contaminated aquifer

    Miroslav Brumovský, Jana Oborná, Petr Lacina, Michal Hegedüs, Ondra Sracek, Jan Kolařík, Martin Petr, Josef Kašlík, Thilo Hofmann, Jan Filip
    2021 - Journal of Hazardous Materials, 405: 124665

    Abstract: 

    In a number of laboratory studies, sulfidated nanoscale zero-valent iron (S-nZVI) particles showed increased reactivity, reducing capacity, and electron selectivity for Cr(VI) removal from contaminated waters. In our study, core-shell S-nZVI particles were successfully injected into an aquifer contaminated with Cr(VI) at a former chrome plating facility. S-nZVI migrated towards monitoring wells, resulting in a rapid decrease in Cr(VI) and Crtot concentrations and a long-term decrease in groundwater redox potential observed even 35 m downstream the nearest injection well. Characterization of materials recovered from the injection and monitoring wells confirmed the presence of nZVI particles, together with iron corrosion products. Chromium was identified on the surface of the recovered iron particles as Cr(III), and its occurrence was linked to the formation of insoluble chromium-iron (oxyhydr)oxides such as CrxFe(1−x)(OH)3(s). Injected S-nZVI particles formed aggregates, which were slowly transformed into iron (oxyhydr)oxides and carbonate green rust. Elevated contents of Fe0 were detected even several months after injection, indicating good S-nZVI longevity. The sulfide shell was gradually disintegrated and/or dissolved. Geochemical modelling confirmed the overall stability of the resulting Cr(III) phase at field conditions. This study demonstrates the applicability of S-nZVI for the remediation of a Cr(VI)-contaminated aquifer.

  • Synergetic Tl and As retention in secondary minerals: An example of extreme arsenic and thallium pollution

    Tamara Dordevic, Petr Drahota, Uwe Kolitsch, Juraj Majzlan, Magdaléna Peřestá, Stefan Kiefer, Michael Stöger-Pollach, Nathalie Tepe, Thilo Hofmann, Tomáš Mikuš, Goran Tasev, Todor Serafimovski, Ivan Boev, Blazo Boev
    2021 - Applied Geochemistry, 135: 105114

    Abstract: 

    Secondary minerals could be effective scavengers of toxic arsenic (As) and thallium (Tl). In environments polluted by mining, these elements are abundant both in acid rock/mine drainage scenarios, as well as in carbonate-buffered environments. In this study we have investigated the behavior of As and Tl during weathering in mine waste dumps and an associated technosol sample from the Crven Dol locality (Allchar Tl–As–Sb–Au deposit, North Macedonia) contaminated with up to 142 g kg−1 of As and 18 g kg−1 of Tl, making it an As- and Tl-extreme environment. We identified As and Tl reservoirs and discuss their difference from those observed in other naturally As- and Tl-rich environments. The pore waters show high concentrations of As (up to 196 mg L−1) and Tl (up to 660 μg L−1). Mild extractions mobilized up to 46% of the total Tl and 11% of the total As, indicating that a large amount of these toxic elements is weakly bound and can be easily mobilized into the environment. Apart from the recognition of Tl storage in several secondary phases (mainly as Tl(I) in members of the pharmacosiderite and jarosite groups, as well as Mn oxides, but also as very minor Tl(III) in other secondary phases), this study also provides the first evidence of Tl uptake by previously unknown thallium arsenate phases (with Tl:As ratios ∼ 2 and 4), detected in carbonate-buffered (near-neutral pH) As- and Tl-rich technosols and waste dumps. These results indicate the need for further studies on Tl speciation in extremely As- and Tl-rich environments.

  • Towards more Sustainable Peptide- based Antibiotics: Stable in Human Blood, Enzymatically Hydrolyzed in Wastewater?

    Michael Zumstein, Kathrin Fenner
    2021 - CHIMIA International Journal for Chemistry, 75: 267-271

    Abstract: 

    The emergence and spread of antibiotic resistance is a major societal challenge and new antibiotics are needed to successfully fight bacterial infections. Because the release of antibiotics into wastewater and downstream environments is expected to contribute to the problem of antibiotic resistance, it would be beneficial to consider the environmental fate of antibiotics in the development of novel antibiotics. In this article, we discuss the possibility of designing peptide-based antibiotics that are stable during treatment (e.g. in human blood), but rapidly inactivated through hydrolysis by peptidases after their secretion into wastewater. In the first part, we review studies on the biotransformation of peptide-based antibiotics during biological wastewater treatment and on the specificity of dissolved extracellular peptidases derived from wastewater. In the second part, we present first results of our endeavour to identify peptide bonds that are stable in human blood plasma and susceptible to hydrolysis by the industrially produced peptidase Subtilisin A.

  • Wildfire-Derived Pyrogenic Carbon Modulates Riverine Organic Matter and Biofilm Enzyme Activities in an In Situ Flume Experiment

    Lukas Thuile Bistarelli, Caroline Poyntner, Cristina Santín, Stefan Helmut Doerr, Matthew V. Talluto, Gabriel Singer, Gabriel Sigmund
    2021 - ACS EST Water, 1648–1656

    Abstract: 

    Wildfires produce large amounts of pyrogenic carbon (PyC), including charcoal, known for its chemical recalcitrance and sorption affinity for organic molecules. Wildfire-derived PyC can be transported to fluvial networks. Here it may alter the dissolved organic matter (DOM) concentration and composition as well as microbial biofilm functioning. Effects of PyC on carbon cycling in freshwater ecosystems remain poorly investigated. Employing in-stream flumes with a control versus treatment design (PyC pulse addition), we present evidence that field-aged PyC inputs to rivers can increase the dissolved organic carbon (DOC) concentration and alter the DOM composition. DOM fluorescence components were not affected by PyC. The in-stream DOM composition was altered due to leaching of pyrogenic DOM from PyC and possibly concurrent sorption of riverine DOM to PyC. Decreased DOM aromaticity indicated by a lower SUVA245 (−0.31 unit) and a higher pH (0.25 unit) was associated with changes in enzymatic activities in benthic biofilms, including a lower recalcitrance index (β-glucosidase/phenol oxidase), suggesting preferential usage of recalcitrant over readily available DOM by biofilms. The deposition of particulate PyC onto biofilms may further modulate the impacts of PyC due to direct contact with the biofilm matrix. This study highlights the importance of PyC for in-stream biogeochemical organic matter cycling in fire-affected watersheds. It was featured on the journal front cover.

  • Wood ash amended biochar for the removal of lead, copper, zinc and cadmium from aqueous solution

    Stuart Cairns, Sampriti Chaudhuri, Gabriel Sigmund, Iain Robertson, Natasha Hawkins, Tom Dunlop, Thilo Hofmann
    2021 - Environmental Technology & Innovation, 24: 1-11

    Abstract: 

    Heavy metals in motorway adjoined aqueous environments have increased at an alarming rate over recent years. This increase has been primarily attributed to anthropogenic activities such as the increase of motor vehicle use. Current remediation techniques, such as balancing ponds have the potential to leave toxic residue with the associated removal costs often proving prohibitive. In this study biochar and wood ash amended biochar were evaluated as remediators of inorganic vehicular pollutants found in motorway runoff, specifically Pb, Cu, Zn and Cd. Biochar from European larch (Larix decidua (L.) Karst.) was produced via fast pyrolysis-gasification (485–530 °C for 90 s) and amended with wood ash post pyrolysis. Pristine larch biochar (BC), larch biochar cold mixed with wood ash (WA) and larch biochar sintered with wood ash (WAS) were studied to evaluate metal immobilisation mechanisms and maximum removal capacities. This study demonstrates that the amendment of biochar with wood ash increases Pb, Cu, Zn, and Cd immobilisation by an order of magnitude compared to BC. The addition of wood ash increases pH whilst adding minerals causing precipitation. Precipitation and ion exchange dominate metal immobilisation and were not correlated to surface area. Sustainability of feedstock, low feedstock/production costs and maximum measured contaminant removal (61.5 mg/g, 38.9 mg/g, 12.1 mg/g and 10.2 mg/g for Pb, Cu, Zn and Cd respectively) indicate that wood ash amended biochar is a viable option to immobilise Pb, Cu, Zn and Cd from motorway runoff.

Book chapters and other publications

3 Publications found
  • Foreword to the research front on ‘Plastics in the Environment’

    Jason Unrine, Thilo Hofmann
    2021 - Environmental Chemistry, 18: 91-92
  • Nanoparticle inventory in a sediment core from the Iron Gate I reservoir

    2021 - JDS4 Scientific Report, 501-510

    Abstract: 

    River sediments are a sink for natural and anthropogenic nanoparticles. Given their risk to harm ecosystems and humans the latter are among contaminants of emerging concern. Here we present multi-element single-particle data of a Danube sediment core, aiming to identify anthropogenic nanoparticles and elucidate their occurrence at different sediment depths. A fly ash dump near Kostolac, Serbia, on the right bank of the Danube River is a likely point source of anthropogenic fly ash particles. Kostolac fly ash particles are enriched in elements such as Cu, Ni, and V. The signatures of these elements within nanoparticles of the sediment core reveal four potential events of fly ash release into the Danube.

  • Natürliche Schwebstoffe in Flüssen: Zusammensetzung, Schlüsselkomponenten und Dynamiken

    2021 - Vom Wasser - das Journal, 51-53