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Per- and polyfluoroalkyl substances (PFAS) have received global public attention because of their wide distribution in aquatic environments and potential adverse effects to humans and wildlife. Due to the lack of analytical standards and the enormous numbers of these compounds, current target-based methods (e.g., LC-MS/MS) are not suitable for the analysis of new/unknown PFAS and transformation products. Therefore, PFAS sum parameter analysis is becoming increasingly important. For PFAS determination of surface waters, solid phase extraction (SPE) is commonly implemented for clean-up and pre-concentration of samples.
Thus, within this work, single-layer SPE methods (based on Strata™-X, Strata™-X-AW, Strata™-NH2 and Oasis-HLB) were investigated for maximum PFAS coverage utilizing extractable organically bound fluorine (EOF) analysis. Thereby, the optimization procedure relied on the analysis of 3 surface water samples in Berlin, Germany, which were affected by the effluent discharge of wastewater treatment plants. To analyse the SPE elution profiles for EOF and inorganic fluorine, high resolution-continuum source-graphite furnace molecular absorption spectroscopy (HR-CS-GFMAS) and ion chromatography (IC) were used, respectively.
Highest EOF concentrations were achieved by using Strata-X/Strata-XAW as SPE sorbents and methanol as eluent. Furthermore, combinations of the most promising SPE sorbents were selected (X/XAW, XAW/X, HLB/X and WAX/GCB) to extract a wider range of PFASs. By comparing multi-layer SPE methods, lower EOF concentrations were obtained for all investigated combination phases compared to the analysed single phases. For the commercially available combination phase Strata-PFAS (WAX/GCB) for all three river water samples, lower EOF concentrations (1.5 times lower) were determined compared to Strata-X.
The results have shown that single-layer SPE systems are currently superior compared to combination phases for PFAS sum parameter analysis. The multi-layer SPE methods need further optimization regarding appropriate sorbent combinations, loading volumes and elution conditions. The developed single-layer SPE methods can help to elucidate pollutions hotspots and discharge routes.
Emission testing of volatile organic compounds (VOC) from materials and products is commonly based on emission test chamber measurements. To ensure the comparability of results from different testing laboratories their measurement performance must be verified. For this purpose, Bundesanstalt für Materialforschung und -prüfung (BAM) organizes an international proficiency test every two years using well-characterised test materials (one sealant, one furniture board and four times a lacquer) with defined VOC emissions. The materials fulfilled the requirements of homogeneity, reproducibility, and stability. Altogether, 41 VOCs were included of which 37 gave test chamber air concentrations between 10 and 98 µg/m³. This is the typical concentration range to be expected and to be quantified when performing chamber tests. Four compounds had higher concentrations between 250 and 1105 µg/m³. The relative standard deviations (RSD) of BAM proficiency tests since 2008 are compared and the improvement of the comparability of the emission chamber testing is shown by the decrease of the mean RSD down to 23% in 2021. In contrast, the first large European interlaboratory comparison in 1999 showed a mean RSD of 51%.
Gypsum (CaSO4∙2H2O) and anhydrite (CaSO4) are among the dominant evaporite minerals in the Atacama Desert [1]. They are distributed ubiquitously, and play a key role in local landscape evolution.
The formation mechanism of especially anhydrite has been a matter of scientific debate for more than a century [2]. To date, there exists no model that can reliably predict anhydrite formation at earth’s surface conditions. While thermodynamics favor its formation [3], it is hardly achieved on laboratory time scales at conditions fitting the Atacama Desert. Long induction times for nucleation have recently been modeled by Ossorio et al. [4]. However, anhydrite can be readily found in the Atacama Desert. Recently, the mineral was synthesized in flow-through reactors as a byproduct of K-jarosite dissolution at high water activity (aw=0.98) and room temperature [5], even-though the thermodynamic stability field begins only under a value of ~0.8. Additionally, recent studies investigated the nano-structure of various calcium-sulfates, which advocate for highly non-classical crystallization behavior [6]. The specific roles of particulates, ionic or organic reagents working as catalysts for the non-classical crystallization pathway remain to be determined.
Here, we present recent results from flow-through experiments as well as analyses of anhydrite samples from the Atacama Desert. Flow-through experiments were performed to systematically explore the domains of flow rate, composition, ionic-strengths and starting materials. Neither primary, nor secondary anhydrite was produced in any of these experiments. Analyses on Atacama samples reveal the existence of at least three distinct anhydrite facies, with differing mineralogy and micro- to nano-structures. The facies are (1) aeolian deposits with sub-µm grain sizes, (2) (sub-)surface nodules that formed from aeolian deposits and (3) selenites with secondary anhydrite rims. Possible mechanisms of their formation will be discussed.
Algal biofilm façades are an alternative to traditional green façades which can help to improve biodiversity and air quality within cities. They present a low maintenance approach in which subaerial algae are grown directly on concrete substrates. The intrinsic bioreceptivity of the substrate is a critical factor in successful facade colonisation. Existing research has identified several environmental and material properties which influence concrete bioreceptivity, however a consensus has yet to be made on which properties are most influential and how the interaction between properties may promote algal biofilm growth under specific conditions.
Even after autoclaving for 2 weeks in the temperature range of 120 to 200 °C, CEM I paste with a water-to-cement ratio of 0.5 still contains some low-crystalline C-S-H. The conversion of low-crystalline C-S-H to crystalline is faster with increasing temperature. The observed low-crystalline and crystalline C-S-H phases (reinhardbraunsite, jaffeite) indicate that the samples have not reached equilibrium yet under these experimental conditions. However, there is a good agreement between experiment and thermodynamic modelling for the other solids indicating that the used datasets are suitable for this application.
Microplastics are solid polymeric particles with a size of 1-1000 μm (ISO/TR21960:2020), which can be emitted from mismanaged waste into the environment, where microplastic is now ubiquitous. What happens to the microplastics after ending up in the environment, which risks entail and what effects it has are not sufficiently clarified up to now. The most certain issue is that the plastic particles in the environment are exposed to natural ageing, are fragmenting and degrading, such that the potential risk to ecosystems and humans is increasing due to the formation of smaller and smaller particles, potentially even including nanoplastics, if these are ingested before their further degradation. Therefore, and in view of a possible registration of polymers under REACH in the future, it is necessary to investigate the degradation of thermoplastic polyurethanes (TPU) regarding hydrolysis stability to evaluate possible risks and effects to the environment.
In the present studies, one thermoplastic polyurethane – with and without hydrolysis stabilizer – is exposed to different pH buffers at 50°C for 14 days to investigate hydrolysis depending to different pH values (acid, alkali and neutral) based on OECD guideline TG111. The hydrolysis behavior of the TPUs is characterized by surface sensitive techniques and on bulk properties. First degradation effects can be detected by SEC. Hydrolysis, especially under acidic and basic conditions, leads to chain scissions to lower molecular masses. Furthermore, the degradation products which indicate the structure of the bulk material were detected by thermo-analytical methods like TGA-FTIR for the small degradation products and the thermo extraction/desorption-gaschromatography/mass spectrometry (TED-GC/MS) for bigger degradation products. Acidic and basic hydrolysis shows the same degradation behavior which is caused by a preferred scission of the ester and urethane functionalities. Surface-sensitive techniques such as XPS demonstrate less carboxylic acid formation at acidic than at alkaline pH value in the TPU without stabilator, where as the TPU with stabilator ages to the same extent in both pH ranges. Altogether, the hydrolysis of TPUs – independently of added stabilizer or not – in acid and alkali environment is accelerated compared to the neutral hydrolysis.
Surfaces of metallic copper and copper alloys effectively inactivate microorganisms and viruses. However, the exact inactivation mode is still under debate. Main factors are assumed to include direct contact with the metallic surface, influx of Cu(I)/Cu(II) ions and the generation of reactive oxygen species (ROS). Laser-induced periodic surface structures (LIPSS) are frequently reported to act antibacterial, mainly by prevention of bacterial adhesion due to a limited number of possible adhesion points or by increasing the overall surface of intrinsically antibacterial materials. In time-kill experiments with E. coli and S. aureus we analyzed the impact of LIPSS on the toxicity of metallic copper and brass. We also conducted ROS accumulation assays and conclude that the application of LIPSS is not generally straight forward to obtain or improve antibacterial surfaces. Thus, the antibacterial effects of LIPPS.
Bacteria are ubiquitous and colonize all types of surfaces, including those in close proximity to humans, such as skin, food, and everyday objects. This raises the question of whether their presence represents a problem to be mitigated or a potential source of benefit to be harnessed, thereby stimulating scientific inquiry into the role of surface-associated bacteria in diverse domains ranging fromhuman health to industrial biotechnology. Aim: The objective of this project is to explore the impact of modifying surface topography on bacterial adhesion behavior. By manipulating the physical characteristics of the substrate, the attachment and detachment dynamics of bacteria can potentially be modified, leading to novel strategies for controlling bacterial colonization in various applications, such as medical devices. Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were tested on LIPSS-covered Fused Silica samples.
Fungal biofilms on materials: describing and modelling growth of the black fungus Knufia petricola
(2023)
Fungi that grow as biofilms are associated with clinical settings as well as various cases of material fouling and material damage. Black fungi as biofilm formers have been rarely studied so far. Their conspicuous dark pigmentation, EPS production, adhesion capabilities and adaptations to stresses allow black fungi to develop biofilms on materials under harsh conditions. For example, rock-inhabiting black fungi withstand sun irradiation and dehydration and are therefore ubiquitous on arid surfaces like solar panels and marble monuments.
To understand and control their ability to colonise and deteriorate materials, one should assess and model black fungi’s growth patterns. But so far, no mathematical model has been developed to describe their growth. Knufia petricola A95, representing rock-inhabiting fungi from Chaetothyriales, is genetically amenable and can serve as a model for biofilm studies in black fungi. The primary objective of this project is to develop a growth model for K. petricola A95 which will enable to define and predict material colonisation of black fungi.
Dedicated experimental work with K. petricola will allow the quantitative assessment of the impact of environmental conditions (e.g. pH, nutrients, etc.) on the growth behaviour at the biofilm and single cells level. Data which will be used to validate and develop an individual-based model (based on the iDynoMICS modelling platform) that explains how fungal biofilms form, colonise materials, and cause deterioration.
Thus far, research has been conducted on the impact of different concentrations and sources of major elements (e.g. C, N, …), as well as trace elements (e.g. Cu, Mg, …), on the colony shape and biomass of Knufia petricola A95 biofilms. To study the behaviour of single cells, the length of the cell cycle in different growth media has been determined via the combined use of microfluidic devices and confocal microscopy.
Dihydroxynaphthalene (DHN) melanin is produced by diverse Ascomycetes via slightly differing biosynthetic routes. The polyketide synthases (PKS) release the heptaketide YWA1, the hexaketide AT4HN or the pentaketide T4HN. The first two products are deacetylated by ‘yellowish-green’ hydrolases to T4HN, and T4HN is further converted by a core set of enzymes to DHN. Final polymerization steps are accomplished by multicopper oxidases. DHN melanogenesis is often regulated in a spatial and temporal fashion resulting e.g., in melanized reproduction and survival structures of the foliar plant pathogen Botrytis cinerea (Schumacher 2016, Mol Microbiol). In contrast, microcolonial black fungi exhibit constitutive melanogenesis. Here, DHN melanin builds a protective layer around all vegetative cells thus contributing to the survival of diverse environmental stresses even without specialized reproduction structures. For studying the regulation and relevance of DHN melanogenesis for tolerance of abiotic and biotic stresses, adhesion to substrates and subsequent damage of colonized surfaces, the rock-inhabiting fungus Knufia petricola was chosen as gene functions in this fungus can be studied by CRISPR/Cas9-based genome editing. The putative melanogenic genes were identified in the genome of K. petricola, deleted to confirm their involvement in DHN melanogenesis and co-expressed in Saccharomyces cerevisiae for reconstruction of the synthesis pathway. Phenotypes of deletion mutants are studied for specifying the functions of DHN melanin in K. petricola.