Phytates represent the most abundant organic phosphorus compounds, occurring primarily as constituents of plant residues in soil. The availability of phytate-related phosphorus to plant nutrition is constrained by the scarce pathways of phytate hydrolysis and can be improved by bio-technological approaches involving microbial bioactivation of soil-bound phosphates. With this purpose, we developed a three-stages experimental methodological framework comprising: 1) selection of beneficial microorganisms, 2) monitoring of phytate decomposition, and 3) indexing of phytase efficiency. Within this framework, we 1) revealed the capability of soil bacteria Bacillus megaterium IMV B-7287, B. megaterium DSM 32, and Kocuria rosea B-42 to metabolize sodium phytate as a sole source of carbon and phosphorus under nutrient limitation highlighting their value for the development of sustainable phosphorus management strategies; 2) combined application of vanado-molybdate photocolorimetry, UV-absorption spectroscopy and fluorescence spectrometry to facilitate the tracing of microbial phytate transformation in solution with a model Na-phytate substrate and the quantitation of phytase efficiency in soil upon rhizobox cultivation; 3) suggested a fluorometric phytate-decomposition ratio as an index expressing the efficiency of phytase activity for quantitation of phytate-originating phosphate released into soil. The applicability of this approach was tested on the rhizosphere of maize. The acquired phytate-decomposition maps show phytase efficiency to be higher in maize-root system developing from bacterized seed. Non-bacterized maize delivers relatively weaker phytate decomposition sites confined within a close root vicinity.

This study evaluates whether existing long-term monitoring data are sufficient to distinguish natural background concentrations from anthropogenic influences on chemical river water quality in Lake Sevan basin. A comprehensive dataset covering physicochemical parameters, nutrients, and trace metals was analyzed for nine major tributaries with different geological settings and land-use characteristics. Multivariate statistical analysis was applied to identify baseline conditions and deviations attributable to human activities. The results indicate that water chemistry is primarily controlled by lithology and hydrological regime, particularly in minimally impacted headwater regions. In contrast, elevated concentrations of nutrients (e.g., nitrate and phosphate) and selected trace elements were associated with agricultural runoff, urban discharge, and localized industrial inputs. Spatial patterns reveal clear gradients of increasing anthropogenic impact downstream and in densely populated sub-basins. The study also demonstrates that, while the current monitoring network is suitable for assessing the overall chemical status of rivers, it is less effective in defining natural background levels and quantifying individual pollution sources due to limited upstream reference conditions. Overall, this approach provides a scientific basis for improved water quality management and policy implementation in the Lake Sevan basin. The findings highlight the importance of integrating long-term monitoring data with statistical tools to support sustainable watershed management in vulnerable catchments.

Uncontrolled mine site leakage poses massive indirect environmental pollution, particularly when harmful substances, like arsenic, infiltrate water bodies, affecting humans. Arsenic contamination, recognized as a severe environmental catastrophe, exemplifies the water quality footprint from a Moroccan cobalt mine supplying electric car construction. Applying the water quality footprint method, we determined that 30-615 m3 of virtual dilution water per electric car would be needed to reduce arsenic pollution below natural background levels in a scenario that assumes that 49 % of the cobalt from the respective mine enters the production of battery materials aligning with recent global cobalt demand and use figures. In such a scenario, this single mine's water quality footprint would constitute up to 0.15 % of Morocco's annual water availability, concerning all electric cars produced annually with cobalt from this mine, and would take up half the annual capacity of one seawater desalination plant. While the databasis ouf our analysis is limited and uncertainties are high, our findings underscore the need to avoid problem shifting so that climate-friendly technologies can develop their potential, prompt reflection on due diligence in supply chains under German and upcoming European legislation and highlight the shared responsibility of industry, society and politics.

The complex composition of dissolved organic matter (DOM) has been extensively studied by modern high-resolution analytical methods. However, DOM reactivity is still enigmatic due to a lack of experimental data with sufficiently high temporal resolution to resolve the intrinsic dynamics within DOM. Likewise, extensive isomeric overlap prevents studying transformation of DOM components with respect to their chemical properties, e.g., molecular polarity. Online ultrahigh-performance liquid chromatography with ultrahigh-resolution mass spectrometry (UHPLC-UHRMS) increases the resolution of isomeric DOM composition across a wide range of polarity. We performed a TiO2-aided photo-irradiation experiment with wastewater treatment plant effluent with high temporal sampling resolution (8 time points, 5 h irradiation). Besides new products (<10%) and removed components (25-60%), intermediate products (IntP) were also found, representing 20-60% of components within distinct polarity fractions. The reaction time to reach the peak magnitude maximum was positively related to the H/C ratio of IntP. About 35% of the DOM components showed different reactivities for different polarity fractions. If applied to experiments in the future, our approach offers new perspectives for biogeochemical interpretation and provides important information for drinking water processing or wastewater treatment with respect to potential toxic IntP.

Tire wear particles (TWP) are a rising issue with emerging ecotoxicological concerns, so that the new Euro 7 regulation is going to set emission limits for tire abrasion. On road surface, TWP incorporate various (non-)traffic related particles (containing heavy metals) forming tire and road wear particles (TRWP). During rainfall, these composite particles are mobilized via drainage systems into the aquatic environment, where TRWP may release incorporated and adsorbed heavy metals from the road into the surrounding water. Consequently, these heavy metals may become bioavailable to aquatic organisms. To evaluate the potential release of heavy metals from TRWP and their bioavailability, we applied a sequential extraction (Community Bureau of Certified References, BCR) to TRWP samples from a highway tunnel and go-kart lanes. For TRWP samples in the aquatic environment, sequential extraction indicated high bioavailability for Cd, Zn (> 50 % under aerobic conditions) and Pb (> 70 % under anaerobic conditions). The relative mobility of the investigated trace elements followed the order: Zn > Pb > Cd >> Cu > Co > As >> Ni > Cr. Furthermore, experiments using river water from the Freiberger Mulde showed that newly adsorbed Cd and Zn on TRWP from the surrounding water are only weakly bound and thus readily bioavailable (Cd > 95 %, Zn > 85 %). These findings indicate that TRWP can significantly influence the mobility and bioavailability of heavy metals in aquatic systems, which is crucial for assessing ecological risks and predicting the potential impact of TRWP as carriers of toxic metals to aquatic biota.

Not only the quality but also the fate of natural organic matter (NOM) is of broad environmental interest. NOM reactivity is insufficiently understood due to a lack of experiments with high temporal resolution, particularly with respect to polarity of NOM molecules. By coupling ultrahigh performance liquid chromatography (UHPLC) with ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), insights into the polarity (hydrophilic versus hydrophobic) of NOM compounds can be obtained.Previous studies addressing NOM reactivity often focused on the fate of molecules – suggesting whether a molecule was degraded, a new molecule was produced, or if the molecule remain unchanged i.e., was resistant to the process of interest. By high time resolution, the reaction time course of molecules can be tracked. Of particular interest is, whether intermediate products can be observed, meaning their abundance initially increases and then decreases during an experiment. In this study, we irradiated a sample from a wastewater treatment plant with light, capturing data with a temporal resolution of 8 time points.Full profile UHPLC-FT-ICR-MS chromatograms were segmented into 13 one-minute wide segments. Molecular formulas were assigned up to masses of 1000 Da by allowing at most two nitrogen atoms and one sulfur as non-oxygen hetero atoms.The main findings indicate that the average (from 13 segments) number of intermediate products (800) was in the same order of magnitude as degraded components (1000). The average number of resistant molecules was lower (250), while the number of products was one order of magnitude smaller (65) compared to the intermediate products. More polar CHNO products and intermediate products were detected compared to CHO, which exhibited a higher number of products, degraded MFs and intermediate products with decreasing polarity. The polarity resolution, as evidenced by chromatographic retention, revealed that the same MF can have different reactivity.From approximately 10,000 assigned MFs more than 2,000 were identified both as degraded and intermediate product, depending on their polarity. About 100 MFs were classified as both products and intermediate products. Notably, at least three reactivity types – product, intermediate product and degraded – could be assigned to about 90 MFs.In conclusion, the investigation of DOM reactivity requires a combination of high mass resolution (FT-ICR-MS), chromatographic / polarity resolution and high temporal or spatial resolution within the experiment time setup.

Lake Bosumtwi in tropical Ghana has been known for its recurrent fish kills, but they have recently been reported to happen less frequently. The lake formed in a meteorite impact crater in Ghana, West Africa. It plays an important role for the local inhabitants for recreation and for fisheries. The lake is deep, and recent observations indicate that recirculation is incomplete. In general, the deep water is anoxic. Fish kills have been associated with the mixing events in the slightly colder rainy season. As unpleasant smells from the water during deep mixing had been reported, the question arose whether toxic gases that had accumulated in the deep water could be responsible; namely, hydrogen sulphide or large amounts of carbon dioxide were considered the most probable candidates. The analysis of the water properties, however, did not detect any hydrogen sulphide nor immensely large concentrations of carbon dioxide. On the contrary, the presence of large amounts of bound nitrogen could be substantiated. We hence concluded that most probably bound nitrogen was responsible for the fish kills on two paths (1) as bound nitrogen as ammonium forms toxic ammonia when mixed into high pH surface water and (2) depletes oxygen when it is oxidized in the surface waters.

Tire wear particles (TWP) are potential pollutants of emerging concern. Therefore, the EU is set to regulate the TWP emissions under the new Euro 7 emission standard. For Germany it is estimated that up to 20,000 t TWP reach the aquatic environment. Main transport pathways are via road runoff and separate sewage systems. Studies indicate that, apart from ecotoxicological concerns, the negatively charged surface of TWP can adsorb heavy metals like Cr, Ni, Zn, Cd and Pb, potentially deteriorating the chemical water quality of rivers. As rivers usually undergo a salt gradient from their source to the sea this may change the adsorption of heavy metals. We investigated the influence of salinity on the heavy metal adsorption on TWP using water samples from the Freiberger Mulde (Saxony, Germany), enriched with NaCl to simulate the salinity representative of different rivers in the Elbe catchment area, and additional water samples (Elbe, Saale, Bode, Schlenze). The adsorption of Cd and Zn appear to be highly salt-dependent. Above 12 mg L-1 Cl-, no significant adsorption was observed. It is assumed that both metals form [MCl4]2- complexes which are repelled from the negative surface of TWP. The potential in building these complexes is high enough to dissolve previously adsorbed Cd from TWP. These findings are important for assessing water quality of river systems as well as runoff filtration and water retention systems. In winter, for instance, when de-icing salt is applied, Cd and Zn bound on TWP may be mobilized entering water systems.

Transformation and degradation of dissolved organic matter (DOM) are of considerable magnitude in large rivers but studies investigating a river system from source to sea are scarce. DOM composition changes from headwaters to tide-impacted river stretches due to natural processes, but is also influenced by anthropogenic impacts on river morphology and water quality. We tested the hypotheses that (1) aromatic, oxygen-rich, and large molecules of terrestrial DOM in upstream regions are transformed to more saturated, nitrogen-rich, and smaller molecules towards the tidal and coastal parts, and (2) chlorophyll a concentration and salinity are important explanatory variables of DOM transformation. We tracked the longitudinal dynamics of DOM composition and relevant drivers along the Elbe River in Central Europe from the Czech headwater region via the lowland freshwater section and the tidal region to the coastal waters of the North Sea applying a Lagrangian sampling approach. Chlorophyll a concentration and oxygen saturation increased longitudinally in the river but showed a distinct minimum in the estuary upstream of the salinity gradient whereas dissolved nutrients were depleted by algae in the freshwater part and were released at algal die-off in the estuary. DOM was dominated by aromatic, oxygen-rich components of terrestrial origin in the upstream region. However, the imprint of this terrestrial signal constantly decreased with increasing river stretch while the proportion of organic nitrogen increased towards the estuary and coastal regions. Analyses of DOM transformations along the river-estuary-ocean gradient revealed that decarboxylation was the most frequent transformation and that phytoplankton and salinity were major explanatory variables of DOM quality. Overall, our unique data set demonstrated a distinct sequence of DOM transformation along the land-ocean gradient highlighting the large activity of riverine and estuarine systems in terms of organic carbon dynamics.

During the last decades, intensive forest dieback due to drought events and bark beetle infestation was globally observed leading to accumulation of deadwood. However, data on molecular composition of deadwood DOM, of its bacterial and photo-transformation, and of the interaction of these processes are scarce. Here, we investigate the fate of DOM leached from deadwood into streams. We hypothesized that (a) bacterial degradation dominates quantitatively over photodegradation in stream water, (b) bacterial degradation is further promoted by labile and easily degradable photoproducts, and (c) DOM compositional changes reflect both the bacterial and light transformation. A leachate of spruce branches and bark in pure water was used for a degradation experiment in a 2 x 2 factorial design without and with stream bacteria and light, respectively. Dissolved organic carbon concentration did not change in dark incubation without bacteria but decreased slightly (3%) in the light. The decrease with bacteria in the dark was stronger (9%), that is, photodegradation of spruce leachate was less important than bacterial degradation (a). Photodegradation and bacterial degradation added in the light plus bacteria treatment (12%), and bacterial degradation was similar in light and dark, indicating no quantitative priming by easily available photoproducts but some qualitative modifications were detected (b). Light induced the production of mostly small and polar molecules, mainly from stream water DOM, while bacteria preferentially degraded nonpolar molecules from dead-wood leachate (c). Our results indicate distinct transformation pathways and high microbial availability for deadwood-derived DOM as compared to stream water DOM that may stimulate heterotrophic processes in headwater streams.

Tire wear particles are an increasing issue in particle emissions to the environment. Germany-wide approximately 100,000 t tire wear particles are emitted every year into the environment which are estimated to be one third of the microplastic emissions. Up to 20% are estimated to reach inland surface waters. Their behavior in the aquatic environment is understudied. Tire wear particles have an overly hydrophobic surface that is capable of adsorbing substances like trace elements. In this study we investigated the adsorption and desorption of trace metals onto and from the particle surface of tire-related samples in water samples of the Freiberger Mulde, a river with naturally elevated concentration of trace elements. The priority trace metals Cr, Ni, Zn, Cd and Pb show a significant adsorption onto the particle surface of tire-related samples. Tire wear particles themselves revealed adsorption of mainly Ni, Cd and Pb. Regarding the German classification for suspended matter in freshwaters, an endangering of the chemical water quality is expected due to the adsorption process and not due to the particles themselves. Upcoming electromobility is expected to increase the Zn (increased tire abrasion) and decrease the Cu amount (reduced brake abrasion) released to freshwaters.

Uncontrolled mine site leakage poses massive indirect environmental pollution, particularly when harmful substances, like arsenic, infiltrate water bodies, affecting humans. Arsenic contamination, recognized as a severe environmental catastrophe, exemplifies the water quality footprint from a Moroccan cobalt mine supplying electric car construction. Applying the water quality footprint method, we determined that 30 to 610 m3 of virtual dilution water per electric car would be needed to reduce arsenic pollution below natural background levels. This single mine's water quality footprint constitutes up to 0.3 % of Morocco's annual water availability, concerning all electric cars produced annually with cobalt from this mine, and corresponds to the full annual capacity of one seawater desalination plant. This underscores the risk of problem shifting with climate-friendly technologies, prompts reflection on due diligence in supply chains under German and upcoming European legislation and highlights the shared responsibility of industry, society and politics.

&lt;p&gt;Natural organic matter (NOM) is often still a black box considering its isomeric composition. From the analytical point of view the highest resolution of NOM can be achieved by Fourier-transform ion cyclotron resonance mass spectroscopy (FT-ICR-MS). This analytical tool generates elemental compositions of thousands of NOM components (molecular formulas, MFs) which can be extracted from aqueous samples (e.g., via solid phase extraction) and which are ionizable (e.g. via electrospray ionization). The comparison of NOM quality in waters of different ecosystems has generated useful insights about ecosystem-specific molecular differences. However, NOM is not an inert mixture of compounds and can undergo chemical changes by photochemical or microbial reactions or adsorptive fractionation. By following the relative intensity changes of single MFs during simple experiments close to nature or monitoring, elucidation of the reactivity of the underlying NOM compounds is possible.&lt;/p&gt; &lt;p&gt;We have combined a photochemical degradation experiment close to nature with monitoring results from two German drinking water reservoirs with the perspective to disentangle photochemical and microbial reactions in the reservoirs. Bacterial induced transformations were widely excluded in the photo degradation experiment by filtration of the sample water before irradiation. During the reservoir monitoring, both microbial and photochemical reactions can be suggested from relative intensity differences of single MFs during lake stratification (between epi- and hypolimnion). MFs show intensity changes both in the photo experiment and in the lake monitoring are regarded as photo labile or photo products. Those MFs with intensity differences only in the lake monitoring can be regarded as microbial reactive.&lt;/p&gt; &lt;p&gt;A great number of highly reactive MFs were found to be present in all samples of both the photo degradation experiment and the lake monitoring. MFs like C&lt;sub&gt;9&lt;/sub&gt;H&lt;sub&gt;12&lt;/sub&gt;O&lt;sub&gt;6&lt;/sub&gt;, C&lt;sub&gt;10&lt;/sub&gt;H&lt;sub&gt;14&lt;/sub&gt;O&lt;sub&gt;6&lt;/sub&gt;, C&lt;sub&gt;10&lt;/sub&gt;H&lt;sub&gt;14&lt;/sub&gt;O&lt;sub&gt;7&lt;/sub&gt;, C&lt;sub&gt;11&lt;/sub&gt;H&lt;sub&gt;16&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt; were photo products, MFs like C&lt;sub&gt;20&lt;/sub&gt;H&lt;sub&gt;16&lt;/sub&gt;O&lt;sub&gt;14&lt;/sub&gt;, C&lt;sub&gt;19&lt;/sub&gt;H&lt;sub&gt;14&lt;/sub&gt;O&lt;sub&gt;13&lt;/sub&gt;, C&lt;sub&gt;18&lt;/sub&gt;H&lt;sub&gt;12&lt;/sub&gt;O&lt;sub&gt;12&lt;/sub&gt; were photo degraded. MFs like C&lt;sub&gt;10&lt;/sub&gt;H&lt;sub&gt;10&lt;/sub&gt;O&lt;sub&gt;7&lt;/sub&gt; and C&lt;sub&gt;9&lt;/sub&gt;H&lt;sub&gt;10&lt;/sub&gt;O&lt;sub&gt;7&lt;/sub&gt; could be suggested to be microbial products because they showed elevated intensity in epilimnetic waters but minor reactivity in the photo experiment.&lt;/p&gt; &lt;p&gt;Our studies (1, 2, 3) provide the attempt to follow NOM reactivity by visualization of single MFs relative intensities versus time and / or space.&lt;/p&gt; &lt;p&gt;1) Wilske, C.et al.,Water MDPI (2020) 12 (2).&lt;/p&gt; &lt;p&gt;2) Herzsprung P. et al., Environ. Sci. Technol. (2020), 54, 13556-13565&lt;/p&gt; &lt;p&gt;3) Wilske C. et al., Water MDPI (2021), 13, 1703.&lt;/p&gt;

Road traffic induced tire wear particles (TWP) attracted widespread attention due to their potential environmental impact. Here, the adsorption process of heavy metals like Pb2+ and Cd2+ on tire wear particles produced by filing (TWP-f) is studied to elucidate the underlying kinetics and thermodynamics. This work includes voltammetric experiments to investigate the concentration and temperature dependency of the adsorption. The adsorption kinetics in buffer solution spiked with heavy metals follows a pseudo-second-order rate equation involving rate-controlling boundary layer adsorption and a side-by-side intraparticle diffusion process. Meanwhile, the adsorption tendencies under the studied conditions for TWP-f were Pb2+ > Cd2+. The equilibrium adsorption data were modulated by the Langmuir, Freundlich, and Dubinin-Radushkevich (DR) isotherms. Both the Freundlich and DR isotherms were found to be feasible for describing the adsorption on TWP-f. The adsorption energy obtained from the DR isotherm is 1.6 kJ mol-1 for Pb2+ and 2 kJ mol-1 for Cd2+, indicating physisorption as the dominating force. According to the Freundlich isotherm, multilayer adsorption is proposed. The thermodynamic parameters show that the adsorption of Pb2+ and Cd2+ is endergonic. Due to small Gibbs enthalpy values near the thermodynamic equilibrium, the adsorption process is mainly dependent on the ambient conditions. So, close-to-nature experiments were conducted to verify the received results. Therefore, tire and road wear particles including road sediments (TRWP+RS) were added to prefiltered freshwater samples of the river Freiberger Mulde (having naturally elevated trace element concentrations). The adsorption kinetics were investigated by ICP-MS/MS emphasizing the pseudo-second-order rate equation. Moreover, it is suggested that the tire wear particles in the TRWP+RS sample are majorly responsible for the adsorption of at least Cd2+.

The decomposition of allochthonous organic matter, such as leaves, is a crucial ecosystem process in low-order streams. Microbial communities, including fungi and bacteria, colonize allochthonous organic material, break up large molecules, and increase the nutritional value for macroinvertebrates. Environmental variables are known to affect microbial as well as macroinvertebrate communities and alter their ability to decompose organic matter. Studying the relationship between environmental variables and decomposition has mainly been realized using leaves, with the drawbacks of differing substrate composition and consequently between-study variability. To overcome these drawbacks, artificial substrates have been developed, serving as standardizable surrogates. In the present study, we compared microbial and total decomposition of leaves with the standardized substrates of decotabs and, only for microbial decomposition, of cotton strips, across 70 stream sites in a Germany-wide study. Furthermore, we identified the most influential environmental variables for the decomposition of each substrate from a range of 26 variables, including pesticide toxicity, concentrations of nutrients, and trace elements, using stability selection. The microbial as well as total decomposition of the standardized substrates (i.e., cotton strips and decotabs) were weak or not associated with that of the natural substrate (i.e., leaves, r² < 0.01 to r² = 0.04). The decomposition of the two standardized substrates, however, showed a moderate association (r² = 0.21), which is probably driven by their similar composition, with both being made of cellulose. Different environmental variables were identified as the most influential for each of the substrates and the directions of these relationships contrasted between the substrates. Our results imply that these standardized substrates are unsuitable surrogates when investigating the decomposition of allochthonous organic matter in streams. Environ Toxicol Chem 2023;42:2007-2018. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

The molecular composition of dissolved organic matter (DOM) is of relevance for global carbon cycling and important for drinking water processing also. The detection of variation of DOM composition as function of time and space from a methodological viewpoint is essential to observe DOM processing and was addressed so far. High resolution concerning DOM quality was achieved with Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS). However almost none of the existing FTICR-MS data sets were evaluated addressing the fate of single mass features / molecular formulas (MFs) abundance during experiments. In contrast to former studies we analyze the function of MF abundance of time and space for such MFs which are present in all samples and which were formerly claimed as recalcitrant in not all but a great number of studies. For the first time the reactivity of MFs was directly compared by their abundance differences using a simple equation, the relative intensity difference (δRI). Search strategies to find out the maximum δRI values are introduced. The corresponding MFs will be regarded as key MFs (KEY-MFs). In order to test this new approach data from a recent photo degradation experiment were combined with monitoring surveys conducted in two drinking water reservoirs. The δRI values varied over one order of magnitude (more than five-fold). MFs like C9H12O6 and C10H14O6 revealed high biogeochemical reactivity as photo products. Some of the KEY-MFs were identical with MFs identified as disinfection byproducts precursors in recent studies. Other KEY-MFs were oxygen-rich and relatively unsaturated (poly-phenol-like) and hence relevant to flocculation procedures.

The European Marine Strategy Framework Directive (MSFD) requires good ecological status of the marine environment. This also includes the Wadden Sea located in the southeastern part of the North Sea and its chemical status of sediments. Based on results from campaigns conducted in the 1980s, 32 surface sediment samples were taken in 2014 to check whether the sampling strategy required for characterizing the trace element content in sediments is representative and to determine the degree of pollution and potential changes over the last decades. For this purpose the elemental mass fractions of 42 elements were assessed in the <= 20 mu m grain size fraction of the surface sediments. Based on cluster analysis a clear correlation between the element distribution and the geographical location of the sampling locations of the German Wadden Sea could be found. As a result of the principal component analysis, three sub-catchments were significantly separated from each other by the characteristic element dis-tributions in the sediments (Norderney and Weser, Elbe and offshore areas, and North Friesland). With the help of discriminant analysis, the classification was confirmed unambiguously. Small anomalies, such as potentially contaminated sites from WWII, could be identified. This proved that the sampling strategy for sediment char-acterization with reference to trace elements in the Wadden Sea of the German Bight is representative. The impact of regulation and changes on the overall sediment quality is most evident when looking at the environmentally critical elements such as As, Cd, Hg, and Cr. For these elements the mean mass fractions show a significant reduction over the last three decades. Current sediments feature only slightly elevated mass fractions of Ag, Cd, Ce, Cs, Nd, Pb and Se at some sampling locations.

Dissolved organic matter (DOM) is ubiquitous in aquatic systems. Discharge of DOM to reservoirs via shallow ground and surface waters from the catchment poses major problems for drinking water production. Knowledge had been generated about mobilization and discharge of DOM in catchments based on the bulk parameter dissolved organic carbon (DOC) (1-3) or on bulk optical parameters describing its quality (4). The decomposition of DOC in catchments and reservoir waters was reported using DOC, bulk optical and carbon isotope analysis (5, 6). For drinking water treatment, removal of humic substances by coagulation / flocculation and the formation of disinfection byproducts are the most pressing challenges. The treatment success depends strongly on the chemical quality of DOM, which probably consists of thousands or even millions of different molecules. The identification of the isomeric structure of each molecule is still far from any instrumental analytical realization. From the analytical point of view the highest resolution of DOM can be achieved by Fourier Transform-Ion Cyclotron Resonance Mass Spectroscopy (FTICR-MS). This analytical tool generates elemental compositions of thousands of DOM components which are water extractable (solid phase extractable DOM, SPE-DOM) and which are ionizable (electrospray ionization, ESI). Using FTICR-MS, knowledge has been generated about the formation potential of disinfection byproducts and its composition (7) and about the flocculation behavior as function of the raw water DOM quality (8). Only few knowledge exists about DOM quality variations in the reservoirs and their catchments based on sum formulas from FTICR-MS analysis (8 - 11). Also little is known about transformations of drinking water treatment relevant sub fractions within the complex DOM in catchments and reservoir waters. As a first result of FTICR-MS measurements we observed that few components (sum formulas) showed high abundance differences as function of depth during reservoir stratification. Some poly-phenol-like components (relevant for flocculation) declined in the epilimnion of a drinking water reservoir potentially due to photo degradation. Some of the (more aliphatic) photo products, which were enriched in the epilimnion, are suspected to be disinfection byproduct precursors. This knowledge can be used to investigate the adaptation of the raw water subtraction depth in the reservoir. 1) Blaurock K et al., Hydrol. Earth Sys. Sci. Disc. (2021), https://doi.org/10.5194/hess 2) Werner BJ et al., Biogeosci. (2019), 16, 4497-4516 3) Musolff A et al., J. Hydrol. (2018), 566, 205-215 4) Da Silva MP et al., Biogeosci. (2020), 17, 5355-5364 5) Kamjunke N et al., Sci. Tot. Environ. (2016), 548-549, 51-59 6) Morling K et al., Sci. Tot. Environ. (2017), 577, 329-339 7) Phungsai P et al., Environ. Sci. Technol. (2018), 52, 3392-3401 8) Raeke J et al., Wat. Res. (2017), 113, 149-159 9) Da Silva MP et al., J. Geophys. Res. Biogeosci. (2021), 126, e2021JG006425 10) Herzsprung P et al., Environ. Sci. Technol. (2020), 54, 13556-13565 11) Wilske C et al., Water MDPI (2021), 13, 1703

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.