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Numerous research results have already pointed towards the negative influence of increased mental stress on educational processes and motivational criteria. It has also been shown that the global public health crisis induced by COVID-19 was related to anxiety symptoms and elevated levels of distress. To holistically elucidate the dynamics of the pandemic-related mental stress of first-year medical students, the associated parameters of three different cohorts were measured at the beginning of the pandemic-related restrictions on university life in Germany (20/21), at the peak of the COVID-19-related restrictions (21/22) and during the easing of the restrictions in the winter term 22/23. In a repeated cross-sectional study design, the constructs of worries, tension, demands and joy were collected from first-year medical students (n = 578) using the Perceived Stress Questionnaire. The results demonstrate significantly increased values of the constructs worries (p < 0.001), tension (p < 0.001) and demands (p < 0.001) at the peak of the pandemic related restrictions compared to the previous and following year as well as significantly decreasing values of general joy of life during the observed period of 3 years (all p-values < 0.001). A confirmatory factor analysis was performed to verify the questionnaire’s factor structure regarding the addressed target group during the pandemic (CFI: 0.908, RMSEA: 0.071, SRMR: 0.052). These data, collected over a period of three years, provide information regarding dynamically manifesting mental stress during the COVID-19 pandemic, and refer to new areas of responsibility for the faculties to adequately counteract future crisis situations.

The variability of the molecular composition of dissolved organic matter (DOM) in soils is predominantly explained by microbial mineralization and assimilation as well as interactions with mineral surfaces and soil organic matter (SOM). From a temperate site with calcareous soil it is established that the molecular composition of DOM shifts from plant-derived towards microorganism-derived signals in soil depth profiles. This variability is largely explained by microbial activity and only to a minor degree by soil-derived parameters like texture and SOM. Here we analyze the molecular composition of DOM in depth profiles of tropical rainforest soils in order to compare its variability to the temperate site as the tropical ecosystems have larger variability in soil texture and mineralogy and lower SOM content. We collected porewater in soil profiles of four ecosystems belonging to two major Amazon rainforest types, terra firme forest on clay soils and white-sand forest on sandy soils. We analyzed the molecular composition of DOM using solid-phase extraction and ultrahigh resolution mass spectrometry.The concentration and composition of DOM differed strongly between the sandy white-sand and clayey terra firme sites. DOM concentration in white-sand soils was much higher and decreased less with depth compared to the terra firme forests. Topsoil DOM in white-sand forests was characterized by high abundance of aromatic plant-derived compounds, whereas it reflected a stronger microbial imprint in terra firme sites. The molecular composition of DOM changed significantly with depth at all sites. In both terra firme and one white-sand forest the transformation was consistent with the expected shift from plant-derived signals towards increasing microbial reworking. The Bray-Curtis dissimilarity between topsoil and greater depth was considerably higher in terra firme compared to white-sand soils with values of 0.32 +- 0.06 and 0.14 +- 0.04, respectively, suggesting much slower DOM transformation in sandy soils. The dissimilarity was correlated similarly to pH, clay content and mineralogy (Pearson R2 = 0.27, 0.21 and 0.23, respectively). The high dissimilarity in the terra firme sites that vary strongly in clay content and mineralogy was only significantly correlated to pH (R2 = 0.16). This suggests that clay content and mineralogy, likely linked to DOM adsorption, were less important for the observed depth trend, which aligns with results from the temperate site. The significant effect of soil pH on the molecular transformation is in line with the importance of microorganisms for DOM transformation as soil pH is a major control on microbial community structure. Overall, our results suggest that similar processes control DOM transformation in temperate and tropical ecosystems, which are likely linked to microbial processing and formation of DOM.

The lake Laacher See (East Eifel, Germany) is affected by eutrophication due to high phosphorous concentration for stagnant waters averaging 34 µg/l (range of 25–40 µg/l P since the year 2000). These elevated concentrations have been monitored since the 1950s and an oligotrophic status could not be achieved despite various measures [2]. A linear correlation was determined between dissolved phosphate (211 – 643 μg/l) and vanadium (6.7 – 28.4 μg/l) in groundwaters of the Ringseitert volcanic complex (West Eifel) with implications for drinking water use [4]. These issues are the motivation to investigate the geogenic input of phosphorous into Laacher See and of vanadium into groundwaters by fluid-rock-interaction.Laacher See is the water-filled crater area of the Plinian-erupted Laacher-See-volcano, which belongs to the East Eifel Volcanic Field with an active volcanism for 0.46 Ma [6]. The catchment of this lake includes rocks of siliciclastic Lower Devonian basement, scoria cones and lava flows of basanitic and tephritic compositions, and phonolithic to foiditic tephra from the Rieden volcanic complex. The youngest volcanic unit is the phonolithic, strong geochemically zoned tephra from the Laacher-See-volcano, which ejected 6 km³ magma in form of pumice and ash 12.9 ka ago [3,6].The dissolution of apatite (primary) and vivianite (secondary phosphate phase) is assumed to be the reason of geogenic input of phosphorous and vanadium by groundwater flow. A particularity of the Laacher See area is the occurrence of mofettes that lead to elevated concentrations of CO2, decreased pH and enhanced apatite dissolution [5]. The hydrochemical modelling program PHREEQC is used to investigate the equilibrium state of phosphate and vanadium in groundwaters at specific Eh/pH-conditions, p(CO2)-values and compositions. In addition, residence times calculated by hydraulic conductivities and dissolution rates from batch experiments are used to distinguish between rate-limited or equilibrium process in phosphate dissolution. Data on phosphorous concentrations and pH of soils in the vicinity of the Laacher See and their equilibrium solutions are evaluated to their geological, geochemical and anthropogenic background and provide clues to phosphorous sources [1].In future studies, bulk rock concentrations will be measured using XRF and total digestion, and detailed dissolution rates will be measured using extended batch experiments to combine these findings into a conceptual hydrogeological model of geogenic phosphate and vanadium input to lake Laacher See.References:[1] Armbruster, M. & Wiesler, F. 2012. Ermittlung der P-Gehalte entlang von 10 Transekten am Laacher See. LUFA Speyer, Speyer. P.24 (unpublished)[2] Block, U. et al. 2015. Übersicht über die Phosphatthematik am Laacher See. Fachhochschule Bingen. P.41[3] Bogaard, P.v.d. & Schmincke, H.U. 1984. The eruptive center of the late quaternary Laacher see tephra. Geologische Rundschau, 73, 933-980, http://doi.org/10.1007/BF01820883.[4] Härter, L.M. et al. 2020. Vorkommen von Vanadium im Grundwasser der Vulkaneifel. Grundwasser, 25, 127-136, http://doi.org/10.1007/s00767-020-00447-x.[5] Pan, H.B. & Darvell, B.W. 2009. Calcium Phosphate Solubility: The Need for Re-Evaluation. Crystal Growth & Design, 9, 639-645, http://doi.org/10.1021/cg801118v.[6] Schmincke, H.-U. 2007. The Quaternary Volcanic Fields of the East and West Eifel (Germany). In: Ritter, J.R.R. & Christensen, U.R. (eds) Mantle Plumes: A Multidisciplinary Approach. Springer Berlin Heidelberg, Berlin, Heidelberg, 241-322, http://doi.org/10.1007/978-3-540-68046-8_8

International audience; In the current study, contrasting growth behaviour of redox sensitive Fe0 nanoparticles (nZVI)was observed on different clay surfaces i.e., 1:1 non-swelling kaolinite (K-nZVI) and 2:1swelling bentonite (B-nZVI). Osmotic swelling of bentonite led to Fe0 nucleation and growthof 5-7 nm size particles in the broadened interlayer spaces. B-nZVI had negative zeta potentialdue to the domination of the surface charge of bentonite clay. Whereas kaolinite has showndominant surface growth of nZVI particles (>24.8±7.4 nm) and positive zeta potential,suggesting domination of Fe0 nanoparticles (nZVI) characteristics. This surface-dependentvariation led to higher and faster removal of oxy-anions with K-nZVI, i.e., chromium andarsenic (87.5 and 157.35 mg/g) than B-nZVI (18.4 and 86.9 mg/g). In comparison, B-nZVI hasshown higher sorption of cations i.e., nickel and cadmium (36 mg/g and 46 mg/g) than K-nZVI(25 and 27 mg/g). XPS and pXRD analysis of reaction precipitates confirmed reductivesorption of chromium, co-precipitation/ complexation of arsenic, electrostatic attraction andcomplexation of nickel and cadmium as major removal mechanisms. Drastically higher totalcontaminant sorption capacities of B-nZVI (327 mg/g) and K-nZVI (372 mg/g) in multicontaminant(Cr+As+Ni+Cd) solutions than individual capacities in mono-ionic solutions wasdue to co-operative effects and newer sites induced via sorption and redox-transformation ofother ionic species. K-nZVI removed chromium and arsenic to below drinking waterpermissible limits whereas B-nZVI succeeded in separating nickel and cadmium to drinkablelevels in groundwater, freshwater, river water, and wastewater samples, emphasizing theirapplicability in high cationic—low anionic and low cationic-higher anionic speciescontaminated waters, respectively.

Anthropogenic phosphorus (P) input from fertilised and unfertilised topsoils into surface water and re-dissolution from sediments can be key drivers of eutrophication. This study aimed to (1) analyse the P input processes into streams/rivers particularly via erosion from fertilised and unfertilised fields and (2) study the effectiveness of the riparian strip in reducing P emissions from diffuse sources. For the investigation, Cambisol-Tschernosem and Luvisol samples from Loess were taken from Thuringian test fields (Germany). Three laboratory simulations were designed to analyse P re-dissolution and leaching behaviour from topsoils and sediments and further extrapolated to a realistic scenario based on the P input path into receiving waters via erosion. Organic bonded phosphorus and orthophosphate were leached out at the beginning. Upscaling to a realistic scenario showed that the main source of P in receiving waters was leaching from sediment interstitial sites (57.5%) via percolation while the P re-dissolution via diffusion (13%), due to two heavy rain events (17%), and leaching from soil interstitial sites (12.5%) only played a minor role. The risk of eutrophication exceeded the threshold total P of 0.10 mg L-1 given as an orientation value by the Federal/State water consortium (LAWA). This was observed in percolates from all sandy soils (0.17–0.85 mg L-1), only slightly in the clayey soils (≤ 0.11 mg L-1) but not in either streambed sediment (≤ 0.08 mg L-1). However, local differences such as steeper slope, different soil compositions such as higher sand and lower clay percentages, and poorer buffering due to lower lime and aluminium content were identified as reasons for a higher risk of eutrophication.

Objectives: Accurate self-assessment and -reflection of competencies are crucial skills for all health professions. The National Competence-Based Learning Objectives Catalogue (NKLM) guiding medical faculties in Germany points out reflection as a non-technical skill and competency-based medical education (CBME) as important approaches. In this context, the role and structure of curricula and skills labs evolved. Especially in peer-assisted trainings, reflection of competencies is important to improve self-regulated learning. Traditionally, we assume self-reflection skills to evolve automatically with learners’ experience. This approach aims to find empirical evidence for this assumption and implements self-reflection of competencies in clinical skills education. Here, we quantify the influence of age and semester of study and its interaction on the concordant self-reflection of students’ own competencies. Methods: Investigation was based on a retrospective analysis of evaluation data from peer-assisted “first aid” and “physical examination” courses in the skills labs of the medical faculty at the Ruhr-University Bochum, Germany. Participants were asked for self-assessed competencies before (pre) and after (post) the course. Additionally, they were asked to retrospectively re-rate their “before” competencies after completing the course (post-pre). Differences between pre and post-pre competencies were assessed as the concordant self-reflection in a moderated regression analysis. Group means and standard deviation were depicted using univariate analysis of variance (ANOVA) with post-hoc Tukey HSD testing in IBM SPSS Statistics V.28. Moderated regression and simple slope analyses were conducted to calculate interaction effects of age and semester of study on the concordant self-reflection. Results: As expected, participants (n = 168) showed significant progress in subjective self-assessment (pre vs. post) in all 18 assessed domains in the course (all p < 0.001). Additionally, participants self-assessed their previous competencies after the course (post-pre) differently than before the course (pre) in 11 out of 18 domains. Hereby, the interaction of age and semester of study explained a significant part of variance in the first aid course (∆R2 = 0.008, ∆F (1;1020) = 8.53, p < 0.005) and in the physical examination course (ΔR2 = 0.03, ΔF (1;10,280) = 10.72, p < 0.001). Conclusions: We quantified that interaction of age and semester has a significant influence on concordant self-reflection skills using a moderated regression analysis. Assumed as an indicator, we conclude that advanced and older students show less differences in pre- vs. post-pre-ratings. This has implications for curriculum development, postulating that an exposure to self-reflection as a metacognitive process should be introduced early in order to train competencies in health professionals. Prospective studies with competency-based assessments are necessary to validate findings.

Chromite ore processing residues (COPR) are real environmental threats, leading to CrO42-, i.e., Cr (VI) leaching into groundwater. It is of serious concern as Cr (VI) is proven to be carcinogenic. Here we emphasize the application of novel and eco-friendly chitin functionalized iron-enriched hydroxyapatite nanocomposite (HAP-Fe0-Ct) in the remediation of Cr (VI)-contaminated groundwater samples collected from Khan Chandpur, India, where the level of Cr (VI) is found to be 11.7 mg/L in a complex aqueous matrix having 793 mg/L of total dissolved solids. Chitin functionality in the composite has resulted in positive zeta potential at circum-neutral pH, favoring electrostatic attraction of chromate ions and resulting in its bulk surface transport. The HAP-Fe0-Ct showed faster kinetics of removal with efficiency (qm = 13.9 ± 0.46 mg/g) for Cr (VI). The composite has shown sorption equilibrium and 100% removal of Cr (VI) within 3 h of interaction time in groundwater samples. No Cr (VI) leaching in the acid wash process at pH 3.5 also suggests chromium’s strong chemisorption onto nanocomposite. During the interaction in aqueous solutions, the reduced iron (Fe0) on the nanocomposite becomes oxidized, suggesting the probable simultaneous reduction of Cr (VI) and its co-precipitation. Continuous column extraction of chromate ions was also efficient in both spiked solutions (39.7 ± 0.04 mg/g) and COPR contaminated water (13.2 ± 0.09 mg/g). Reusability up to three cycles with almost complete Cr (VI) removal may be attributed to surface protonation, new binding sites generation, and electron transfer from Fe0 core through defects. The study concludes that HAP-Fe0-Ct could be utilized for continuous Cr (VI) removal from COPR contaminated complex groundwater matrices.

It is our great pleasure to briefly introduce our motivation to collect scientific contributions for this Special Issue, entitled “Nano Geochemistry” [...]

Fungi living in heavy metals and radionuclides contaminated environments, namely the Chernobyl Exclusion Zone need to be able to cope with these pollutants. In this study, the wood-rot fungus Schizophyllum commune was investigated for its metal tolerance mechanisms, and for its ability to transport such metals through its hyphae. Effects of temperature and pH on tolerance of Cs, Sr, Cd, and Zn were tested. At concentrations allowing for half-maximal growth, adapted strains were raised. The strontium-adapted strain, S. commune 12-43 Sr, showed transport of specifically Sr over distances on a cm-scale using split plates. The adaptation did not yield changes in cell or colony morphology. Intracellular metal localization was not changed, and gene expression profiles under metal stress growing on soil versus artificial medium showed a higher impact of a structured surface for growth on soil than with different metal concentrations. In the transcriptome, transporter genes were mostly down-regulated, while up-regulation was seen for genes involved in the secretory pathway under metal stress. A comparison of wildtype and adapted strains could confirm lower cellular stress levels leading to lack of glutathione S-transferase up-regulation in the adapted strain. Thus, we could show metal transport as well as specific mechanisms in metal stress avoidance.

The Long-term In-situ Test (LIT) of the Colloid Formation and Migration project (CFM) at the Grimsel Test Site, investigates the generation of bentonite colloids and, hence, radionuclide mobilization within a well-defined and controlled shear zone in a crystalline rock. In this context, the determination of radionuclide aqueous speciation is essential to understand whether radionuclides are easily transported or immobilized by precipitation or uptake processes in the bentonite barrier included in a repository concept for nuclear waste, and mimic in the LIT experiment. The objective of this work is to determine the aqueous speciation of seven radionuclides (i.e. 75Se(VI), 99Tc(VII),233U(VI), 237Np(V), 241Am(III), Th(IV) and 242Pu(IV)) by thermodynamic calculations in different water compositions representing the geochemical evolution through the LIT. A comparison of the results obtained from two different modelling groups allows the identification of the geochemical key parameters affecting radionuclide mobility in this context and the corresponding numerical and conceptual uncertainties. Particularly, silicate complexes of trivalent actinides and uranium(VI) carbonato complexes (i.e. CanUO2(CO3)3(4-2n) n = 1 or 2) seem to be crucial in these environments, even at reducing conditions. Conceptual uncertainties like inclusion/exclusion of tetravalent actinide-bearing colloids formation and polyselenides have clearly been identified.

In the frame of studies on the safe disposal of nuclear waste, there is a great interest for understanding the migration behavior of 99Tc. 99Tc originating from nuclear energy production and global fallout shows environmental levels down to 107 atoms/g of soil (∼2 fg/g). Extremely low concentrations are also expected in groundwater after diffusion of 99Tc through the bentonite constituting the technical barrier for nuclear waste disposal. The main limitation to the sensitivity of the mass spectrometric analysis of 99Tc is the background of its stable isobar 99Ru. For ultratrace analysis, the Accelerator Mass Spectrometry (AMS) setup of the Technical University of Munich using a Gas-Filled Analyzing Magnet System (GAMS) and a 14 MV Tandem accelerator is greatly effective in suppressing this interference. In the present study, the GAMS setup is used for the analysis of 99Tc in samples of the seawater reference material IAEA-443, a peat bog lake, and groundwater from an experiment of in situ diffusion throug...

To assess a reliable safety case for future deep underground repositories for highly active nuclear waste the retention of radionuclides by the surrounding host rock must be understood comprehensively. Retention is influenced by several parameters such as mineral heterogeneity and surface roughness, as well as pore water chemistry (e.g., pH). However, the interplay between those parameters is not yet well understood. Therefore, we present a correlative spectromicroscopic approach to investigate sorption of the actinide Cm(III) on: 1) bulk K-feldspar crystals to determine the effect of surface roughness and pH (5.5 and 6.9) and 2) a large feldspar grain as part of a complex crystalline rock system to observe how sorption is influenced by the surrounding heterogeneous mineralogy. Our findings show that rougher K-feldspar surfaces exhibit increased Cm(III) uptake and stronger complexation. Similarly, increasing pH leads to higher surface loading and stronger Cm(III) binding to the surface. Within a heterogeneous mineralogical system sorption is further affected by neighboring mineral dissolution and competitive sorption between mineral phases such as mica and feldspar. The obtained results express a need for investigating relevant processes on multiple scales of dimension and complexity to better understand trivalent radionuclide retention by a potential repository host rock.