4 Material und Umwelt
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The leaching behavior of scandium (Sc) from bauxite residues can differ significantly when residues of different geological backgrounds are compared. The mineralogy of the source rock and the physicochemical environment during bauxitization affect the association of Sc in the bauxite i.e., how Sc is distributed amongst different mineral phases and whether it is incorporated in and/or adsorbed onto those phases. The Sc association in the bauxite is in turn crucial for the resulting Sc association in the bauxite residue. In this study systematic leaching experiments were performed on three different bauxite residues using a statistical design of experiments approach. The three bauxite residues compared originated from processing of lateritic and karstic bauxites from
Germany, Hungary, and Russia. The recovery of Sc and Fe was determined by ICP-OES measurements. Mineralogical changes were analyzed by X-ray-diffraction and subsequent Rietveld refinement. The effects of various parameters including temperature, acid type, acid concentration, liquid-to-solid ratio and residence time were studied. A response surface model was calculated for the selected case of citric acid leaching of Hungarian bauxite residue. The investigations showed that the type of bauxite residue has a strong influence. The easily leachable fraction of Sc can vary considerably between the types, reaching ~20–25% in German Bauxite residue and ~50% in Russian bauxite residue. Mineralogical investigations revealed that a major part of this fraction was released from secondary phases such as cancrinite and katoite formed during Bayer processing of the bauxite.
The effect of temperature on Sc and Fe recovery is strong especially when citric acid is used. Based on the exponential relationship between temperature and Fe-recovery it was found to be particularly important for the selectivity of Sc over Fe. Optimization of the model for a maximum Sc recovery combined with a minimum Fe
recovery yielded results of ~28% Sc recovery at <2% Fe recovery at a temperature of 60 ◦C, a citric acid normality of 1.8, and a liquid-to-solid ratio of 16 ml/g. Our study has shown that detailed knowledge about the Sc association and distribution in bauxite and bauxite residue is key to an efficient and selective leaching of Sc
from bauxite residues.
Water is generally considered to be an undesirable substance in fuel system, which may lead to microbial contamination. The antibacterial strategies that can turn water into things of value with high disinfection efficacy have been urgently needed for fuel system. Here, we reveal a water-fueled autocatalytic bactericidal pathway comprised by bi-metal micro-electrode system, which can spontaneously produce reactive oxygen species (mainly H2O2 and O2•–) by the electron Fenton-like reaction in water medium without external energy., The respiratory chain component of bacteria and the galvanic corrosion on the coated metals were two electron sources in the system. The specific model of Ag-Ru water-fueled autocatalytic (WFA) microelectrode particles presents extremely high disinfection efficiency (>99.9999%) in less than one hour for three aerobic bacteria (Escherichia coli, Pseudomonas aeruginosa and Bacillus subtilis) in LB media and high disinfection efficiency for the anaerobic bacteria (Desulfovibrio alaskensis) in Postgate E media without natural light irradiation. Overall, the novel WFA Ag-Ru antibacterial material explored in this study has a high potential for sterilizing applications in fuel system and this work provides the potential for the development of non-chemical and water-based antibacterial materials, such as WFA Ag-Ru antibacterial coating on stainless steel.
Numerous non-native tree species are given attention with respect to the reforestation of calamity areas in Europe. Among them, several species may form durable wood which can be used for outdoor applications, but differences in wood durability are expected between original and European growth sites. This study aimed at examining the biological durability against wooddestroying fungi and water permeability of German-grown Dawn redwood (Metasequoia glyptostroboides) and Port Orford cedar (Chamaecyparis lawsoniana). The heartwood of both wood species was assigned to durability class 4 (DC 4, less durable) in soil contact and DC 1–4 (very to less durable) against wood-destroying basidiomycetes. However, according to the Meyer-Veltrup model, their material resistance dose was notably higher compared to the reference species Norway spruce (Picea abies), and the resulting service life of above ground structures should be a multiple of the reference.
Industrial and agricultural waste streams (waste water, sludges, tailings, etc.) which contain high concentrations of NH4+, PO43–, and transition metals are environmentally harmful and toxic pollutants. At the same time, phosphorous and transition metals constitute highly valuable resources. Typically, separate pathways have been considered to extract hazardous transition metals or phosphate independently from each other. Investigations on the simultaneous removal of multiple components have been carried out only to a limited extent. Here, we report the synthesis routes for Ni- and Co-struvites (NH4MPO4·6H2O, M = Ni2+ and Co2+), which allow for P, ammonia, and metal co-precipitation. By evaluating different reaction parameters, the phase and stability of transition metal struvites as well as their crystal morphologies and sizes could be optimized. Ni-struvite is stable in a wide reactant concentration range and at different metal/phosphorus (M/P) ratios, whereas Co-struvite only forms at low M/P ratios. Detailed investigations of the precipitation process using ex situ and in situ techniques provided insights into the crystallization mechanisms/crystal engineering of these materials. M-struvites crystallize via intermediate colloidal amorphous nanophases, which subsequently aggregate and condense to final crystals after extended reaction times. However, the exact reaction kinetics of the formation of a final crystalline product varies significantly depending on the involved metal cation in the precipitation process: several seconds (Mg) to minutes (Ni) to hours (Co). The achieved level of control over the morphology and size makes precipitation of transition metal struvites a promising method for direct metal recovery and binding them in the form of valuable phosphate raw materials. Under this paradigm, the crystals can be potentially up-cycled as precursor powders for electrochemical or (electro)catalytic applications, which require transition metal phosphates.
Antimicrobial resistance (AMR) is a global health problem with the environment being an important compartment for the evolution and transmission of AMR. Previous studies showed that de-novo mutagenesis and horizontal gene transfer (HGT) by conjugation or transformation – important processes underlying resistance evolution and spread - are affected by antibiotics, metals and pesticides. However, natural microbial communities are also frequently exposed to biocides used as material preservatives, but it is unknown if these substances induce mutagenesis and HGT. Here, we show that active substances used in material preservatives can increase rates of mutation and conjugation in a species- and substance-dependent manner, while rates of transformation are not increased. The bisbiguanide chlorhexidine digluconate, the quaternary ammonium compound didecyldimethylammonium chloride, the metal copper, the pyrethroid-insecticide permethrin, and the azole-fungicide propiconazole increase mutation rates in Escherichia coli, whereas no increases were identified for Bacillus subtilis and Acinetobacter baylyi.
Benzalkonium chloride, chlorhexidine and permethrin increased conjugation in E. coli. Moreover, our results show a connection between the RpoS-mediated general stress and the RecA-linked SOS response with increased rates of mutation and conjugation, but not for all biocides. Taken together, our data show the importance of assessing the contribution of material preservatives on AMR evolution and spread.
Electron microscopy (EM) is the gold standard for the characterisation of the morphology (size and shape) of nanoparticles. Visual observation of objects under examination is always a necessary first step in the characterisation process. Several questions arise when undertaking to identify and count particles to measure their size and shape distribution. In addition to challenges with the dispersion and identification of the particles, more than one protocol for counting particles is in use. This paper focuses on precise rules for the counting of particles in EM micrographs, as this influences the measurement accuracy of the number of particles, thus implicitly affecting the size values of the counted particles. We review and compare four different, commonly used methods for counting, which we then apply in case studies. The impact of the selected counting rule on the obtained final particle size distribution is highlighted. One main aim of this analysis is to support the application of a specific, well-defined counting approach in accordance with regulatory
requirements to contribute to achieving more reliable and reproducible results. It is also useful for the new harmonised measurement procedures for determining the particle size and particle size distribution of nanomaterials.
Rechtliche Vorgaben der Klärschlammverordnung und deren Auswirkungen auf die Phosphor-Rückgewinnung
(2022)
Im Abfalltechnik-Ausschuss der Bund/Länder-Arbeitsgemeinschaft Abfall (LAGA) wurde eine Vollzugshilfe zur Klärschlammverordnung erarbeitet, die nach Verabschiedung durch die Umweltministerkonferenz Mitte Mai 2020 als LAGA-Merkblatt M-39 veröffentlicht wurde. Im vorliegenden vierten Arbeitsbericht der DWA-Arbeitsgruppe KEK-1.1 werden verschiedene Aspekte der ab dem Jahr 2029 geltenden Regelungen aufgegriffen und damit einige Punkte des LAGA M-39 hinsichtlich der technischen Auswirkungen für den Kläranlagenbetreiber konkret ausgeführt.
Background: Host–pathogen interactions can lead to dramatic changes in host feeding behaviour. One aspect of this includes self-medication, where infected individuals consume substances such as toxins or alter their macronutrient consumption to enhance immune competence. Another widely adopted animal response to infection is illness-induced anorexia, which is thought to assist host immunity directly or by limiting the nutritional resources available to pathogens. Here, we recorded macronutrient preferences of the global pest cockroach, Blatta orientalis to investigate how shifts in host macronutrient dietary preference and quantity of carbohydrate (C) and protein (P) interact with immunity following bacterial infection.
Results: We fnd that B. orientalis avoids diets enriched for P under normal conditions, and that high P diets reduce cockroach survival in the long term. However, following bacterial challenge, cockroaches signifcantly reduced their overall nutrient intake, particularly of carbohydrates, and increased the relative ratio of protein (P:C) consumed. Surprisingly, these behavioural shifts had a limited efect on cockroach immunity and survival, with minor changes to immune protein abundance and antimicrobial activity between individuals placed on diferent diets, regardless of infection status.
Conclusions: We show that cockroach feeding behaviour can be modulated by a pathogen, resulting in an illness-induced anorexia-like feeding response and a shift from a C-enriched to a more P:C equal diet. However, our results also indicate that such responses do not provide signifcant immune protection in B. orientalis, suggesting that the host’s dietary shift might also result from random rather than directed behaviour. The lack of an apparent beneft of the shift in feeding behaviour highlights a possible reduced importance of diet in immune regulation in these invasive animals, although further investigations employing pathogens with alternative infection strategies are warranted.
Zur Weiterentwicklung der Probenpräsentation wurde ein Adapter entwickelt, der Emissionsprüfkammer und Bewertungstrichter miteinander verbindet und dadurch eine der direkten Messung vergleichbare Geruchsbewertung ermöglicht. Die analytischen Messungen zeigen, dass es kaum Unterschiede in der Zusammensetzung der Probenluft in der Kammer im Vergleich zum Probenbehälter gibt. Bei den olfaktorischen Messungen kam es jedoch bei der Bewertung der Probenluft mit Hilfe des Adapters zu Minderbefunden. Anschließende Untersuchungen zeigten, dass beim Ausschalten des Geräts Umgebungsluft über den Trichter in den Adapter strömt und zu einer Verdünnung der Probenluft führt. Um dies zu vermeiden, werden derzeit weitere Messungen durchgeführt.
Eine weitere Versuchsreihe wurde durchgeführt, um den Messaufwand bei der Bewertung der empfundenen Intensität zu reduzieren. Die entwickelte „größer-oder-kleiner/gleich“ Abfrage kann hier hilfreich sein. Die Untersuchungen im Luftqualitätslabor und im Rahmen eines Ringversuches mit verschiedenen Laboren, zeigen, dass die Abfrage in fast allen Fällen zu den gleichen Ergebnissen führt, wie die normgerechte aber aufwendigere Ermittlung der empfundenen Intensität mithilfe des Vergleichsmaßstabes.
The roles extracellular polymeric substances (EPS) play in mineral attachment and weathering were studied using genetically modified biofilms of the rock-inhabiting fungus Knufia petricola strain A95. Mutants deficient in melanin and/or carotenoid synthesis were grown as air-exposed biofilms. Extracted EPS were quantified and characterised using a combination of analytical techniques. The absence of melanin affected the quantity and composition of the produced EPS: mutants no longer able to form melanin synthesised more EPS containing fewer pullulan-related glycosidic linkages. Moreover, the melanin-producing strains attached more strongly to the mineral olivine and dissolved it at a higher rate. We hypothesise that the pullulan-related linkages, with their known adhesion functionality, enable fungal attachment and weathering. The released phenolic intermediates of melanin synthesis in the Δsdh1 mutant might play a role similar to Fe-chelating siderophores, driving olivine dissolution even further. These data demonstrate the need for careful compositional and quantitative analyses of biofilm-created microenvironments.
Nine different bacterial isolates were recovered from landfills. Each isolate was obtained in pure culture. As a consortium, the bacteria degrade polyethylene. The complete genome sequence of strain G2 was determined by PacBio sequencing. Using the TYGS server for taxonomic classification, strain G2 was assigned to the species Pseudomonas veronii.
For more than 110 years, BAM has been producing reference materials for a wide range of application fields. With the development of new analytical methods and new applications as well as continuously emerging more stringent requirements of laboratory accreditation with regard to quality control and metrological traceability, the demand and requirements for reference materials are increasing. This trend article gives an overview of general developments in the field of reference materials as well as developments in selected fields of application in which BAM is active. This includes inorganic and metal analysis, gas analysis, food and consumer products, and geological samples. In addition to these more traditional fields of application, developments in the areas of optical spectroscopy, particulary fluorescence methods, and nanomaterials are considered.
Warum eine Kreislaufwirtschaft ohne Abfallverbrennung nicht funktionieren wird, beschreibt die Dechema im Positionspapier „Abfallverbrennung in der Zukunft“. Experten der Fachgruppe „Abfallbehandlung und Wertstoffrückgewinnung“ von ProcessNet, einer gemeinsamen Initiative der Dechema und der VDI-Gesellschaft Verfahrenstechnik und Chemieingenieurwesen, haben es erstellt.
Cellulose ethers, like methyl cellulose (MC) or hydroxypropyl cellulose (HPC), are widely used in conservation. They also occur as additives and rheology modifiers in various products like dispersions or gels. Do such products release harmful volatile organic compounds (VOC) during their accelerated aging? A mass testing series utilizing the Oddy test of 60 commercial cellulose ethers ranks the products in safe for permanent use (P, no corrosion), only for temporary use (T, slight corrosion), and unsuitable at all (F, heavy corrosion). Results show that 55% of the products passed the test whereas 33% are for temporary use as slight corrosion occurred on at least one metal coupon and only 11% failed the Oddy test. Raman measurements of the corrosion products identified oxides like massicot, litharge, cuprite, and tenorite among carbonates (hydrocerussite, plumbonacrite), and acetates like basic lead acetate, lead acetate trihydrate as well as lead formate as main phases. For example, commercial, industrial Klucel® G (HPC) scored a T rating through slight corrosion on the lead coupon. Basic lead acetate among other phases indicates the presence of acetic acid. Additional measurements of the sample with thermal desorption GC–MS utilizing the BEMMA scheme confirm the high acetic acid outgassing and reveal the presence of a small amount of formaldehyde.
Nine different bacterial isolates were recovered from landfills. Each isolate was obtained in pure culture. As a consortium, the bacteria degrade polyethylene. The complete genome sequence of strain G9 was determined by PacBio sequencing. Using the TYGS server for taxonomic classification, strain G9 was assigned to the species Micromonospora aurantiaca.
Herein we report the synthesis of a zeolitic imidazolate framework (ZIF-8) by an easy “mix and wait” procedure. In a closed vial, without any interference, the mixture of 2-methylimidazole and basic zinc carbonate assembles into the crystalline product with approx. 90% conversion after 70 h. The reaction exhibits sigmoidal kinetics due to the self-generated water which accelerates the reaction.
The environmental impact assessment of materials is usually based on laboratory tests, mostly in combination with models describing the longterm fate of the substances of interest in the targeted environmental compartment. Thus, laboratory tests are the fundamental link to achieve appropriate assessment conclusions which makes it essential to generate consistent results. This just as applies to the leaching of cementitious materials. In Europe, the leaching behavior of monolithic building materials is tested in the Dynamic Surface Leaching Test following the specification CEN/TS 16637–2. An interlaboratory comparison on European level regarding this technical specification showed relatively high intra- and interlaboratory variations for the tested materials (monolithic copper slag and cement stabilized coal fly ash). Therefore the German Committee for Structural Concrete (DAfStb) framed a guideline to specify additional testing conditions for cementitious materials. To assess the possible improvement by this guidelines measures, a round robin test with 11 participants from Germany and the Netherlands was conducted. This work aims to provide insight into the factors to be considered in the testing of alkaline materials, including sample preparation, and highlights crucial procedures and their manifestation in the results. All evaluated parameters showed improved results compared to the earlier round robin test. The relative standard deviations for repeatability (RSDr) and reproducibility (RSDR) of the elements calcium, barium, antimony, chromium, molybdenum and vanadium, which are the parameters evaluated in both round robin tests, were RSDr = 4%, 4%, 2%, 5%, 5%, and 5% respectively (4% in average) for this work, in comparison to the European round robin test with an average RSDr of 29% (17%, 17%, 20%, 40%, 36%, and 42%). The RSDR improved from 41% (30%, 36%, 29%, 57%, 40%, and 56%) to 14% (12%, 8%, 6%, 28%, 15%, and 12%). CO2 ingress during testing and the inaccuracy of eluate analytics for concentrations close to the determination limits were identified as the main sources of error.
Black microcolonial fungi (Ascomycetes from Arthonio-, Dothideo-, and Eurotiomycetes) are stress-tolerant and persistent dwellers of natural and anthropogenic extreme habitats. They exhibit slow yeast-like or meristematic growth, do not form specialized reproduction structures and accumulate the black pigment 1,8-dihydroxynaphthalene (DHN) melanin in the multilayered cell walls. To understand how black fungi live, survive, colonize mineral substrates, and interact with phototrophs genetic methods are needed to test these functions and interactions. We chose the rock inhabitant Knufia petricola of the Chaetothyriales as a model for developing methods for genetic manipulation. Here, we report on the expansion of the genetic toolkit by more efficient multiplex CRISPR/Cas9 using a plasmid-based system for expression of Cas9 and multiple sgRNAs and the implementation of the three resistance selection markers genR (geneticin/nptII), baR (glufosinate/bar), and suR (chlorimuron ethyl/sur). The targeted integration of expression constructs by replacement of essential genes for pigment synthesis allows for an additional color screening of the transformants. The black-pink screening due to the elimination of pks1 (melanin) was applied for promoter studies using GFP fluorescence as reporter. The black-white screening due to the concurrent elimination of pks1 and phs1 (carotenoids) allows to identify transformants that contain the two expression constructs for co-localization or bimolecular fluorescence complementation (BiFC) studies. The co-localization and interaction of the two K. petricola White Collar orthologs were demonstrated. Two intergenic regions (igr1, igr2) were identified in which expression constructs can be inserted without causing obvious phenotypes. Plasmids of the pNXR-XXX series and new compatible entry plasmids were used for fast and easy generation of expression constructs and are suitable for a broad implementation in other fungi. This variety of genetic tools is opening a completely new perspective for mechanistic and very detailed study of expression, functioning and regulation of the genes/proteins encoded by the genomes of black fungi.
The diffusive gradients in thin-films (DGT) technique shows in many publications a superior correlation to the amount of plant-available phosphorus (P) in soil. However, this technique cannot give information on the plant-available P species in soil. Therefore, we combined DGT with solution 31P nuclear magnetic resonance (NMR) spectroscopy. This was achieved by using a modified DGT device in which the diffusive layer had a larger pore size, the binding layer incorporated an adsorption material with a higher capacity, and the device had a larger exposure area. The spectroscopic investigation was undertaken after elution of the deployed DGT binding layer in a NaOH solution. Adsorption tests using solutions of known organic P compounds showed that a sufficient amount of these compounds could be adsorbed on the binding layer in order for them to be analyzed by solution 31P NMR spectroscopy. Furthermore, various intermediates of the hydrolysis of trimetaphosphate in soil could be also analyzed over time.
The halophilic γ-proteobacterium Halomonas elongata DSM 2581T thrives at salt concentrations well above 10 % NaCl (1.7 M NaCl). A well-known osmoregulatory mechanism is the accumulation of the compatible solute ectoine within the cell in response to osmotic stress. While ectoine accumulation is central to osmoregulation and promotes resistance to high salinity in halophilic bacteria, ectoine has this effect only to a much lesser extent in non-halophiles. We carried out transcriptome analysis of H. elongata grown on two different carbon sources (acetate or glucose), and low (0.17 M NaCl), medium (1 M), and high salinity (2 M) to identify additional mechanisms for adaptation to high saline environments. To avoid a methodological bias, the transcripts were evaluated by applying two methods, DESeq2 and Transcripts Per Million (TPM). The differentially transcribed genes in response to the available carbon sources and salt stress were then compared to the transcriptome profile of Chromohalobacter salexigens, a closely related moderate halophilic bacterium. Transcriptome profiling supports the notion that glucose is degraded via the cytoplasmic Entner-Doudoroff pathway, whereas the Embden-Meyerhoff-Parnas pathway is employed for gluconeogenesis. The machinery of oxidative phosphorylation in H. elongata and C. salexigens differs greatly from that of non-halophilic organisms, and electron flow can occur from quinone to oxygen along four alternative routes. Two of these pathways via cytochrome bo' and cytochrome bd quinol oxidases seem to be upregulated in salt stressed cells. Among the most highly regulated genes in H. elongata and C. salexigens are those encoding chemotaxis and motility proteins, with genes for chemotaxis and flagellar assembly severely downregulated at low salt concentrations. We also compared transcripts at low and high-salt stress (low growth rate) with transcripts at optimal salt concentration and found that the majority of regulated genes were down-regulated in stressed cells, including many genes involved in carbohydrate metabolism, while ribosome synthesis was up-regulated, which is in contrast to what is known from non-halophiles at slow growth. Finally, comparing the acidity of the cytoplasmic proteomes of non-halophiles, extreme halophiles and moderate halophiles suggests adaptation to an increased cytoplasmic ion concentration of H. elongata. Taken together, these results lead us to propose a model for salt tolerance in H. elongata where ion accumulation plays a greater role in salt tolerance than previously assumed.