Displays

Plant protection products (PPPs) are used routinely in modern agriculture and they can reach surface waters from treated fields or equipment handling areas. Assessing water contamination for a broad set of PPPs is challenging due to the episodic occurrence of concentration peaks. The traditional workflow of taking samples in the field, transferring to the lab, possible storing, and sample preparation and analysis strongly limits sampling frequency and duration of sampling campaign, in particular for labile PPPs.

Here we present for the first time results from the on-site platform MS²field quantifying hundreds of PPPs with 20 minutes temporal resolution continuously yielding concentrations in real-time. MS²field is a fully automated mobile unit to be deployed in the field, where it collects water samples and performs target and non-target high-resolution mass spectrometry with limits of quantification in the low range of ng/l. For the presented application, MS²field was deployed in a small agricultural catchments in 2019 (May – July, 41 days of observation) in the Swiss Plateau close to Lake Constance. This application resulted in 3000 samples, which can be analyzed for up to 600 compounds yielding 1.8 million measured concentrations.

The high temporal resolution allows first for a proper quantification of peak concentration. Overall, the time-series encompassed nine rain events, during which extreme concentration peaks occurred. The fungicides fluopyram achieved 30 µg/l and cyprodinil exceeded 5 µg/l, while the herbicide napropamide reached 5 µg/l. Also during dry periods, high concentrations were observed: fungicides peaked to 2 µg/l, herbicides to 0.9 µg/l, and insecticides to 0.1 µg/l.

Yet, the temporal resolution makes it possible to investigate in great detail the PPPs dynamics during rainfall events of different characteristics yielding insights about potential PPPs sources and pathways. To that end, we compared the measured concentrations of tens of selected PPPs with meteorological observations and water level data available at 10 minutes resolution for the different events.

The high-time resolution relationships between measured concentrations and water levels of these compounds revealed interesting patterns. For the same PPP, the patterns generally differed widely across different rainfall events. For some groups of different PPPs we observed very similar patterns during the same event. However, this similarity did not always hold across different events. This suggests that the patterns were controlled by event-specific combinations of PPPs availability and hydrological response in different parts of the catchment.

The measured concentrations-water level relationships were often hysteretic in nature. Supply limitation and transport limitation might control hysteresis. Supply limitation may refer to the lack of PPP residues in the environment; otherwise, strong adsorption can decrease PPPs availability. Transport limitation may predominate during hydrological conditions not suitable for a substantial mobilization and movement of PPPs. Comparison of different hysteresis patterns shall provide insights into the interplay between site- and event-specific mobilization of PPPs and their chemical properties leading to the understanding of how to minimize water contamination in the future.

How to cite: la Cecilia, D., Dax, A., Stravs, M., Ort, C., Singer, H., and Stamm, C.: Continuous high-frequency pesticides monitoring reveals underestimated environmental threats and unique insights into transport patterns, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9601, https://doi.org/10.5194/egusphere-egu2020-9601, 2020.

In many countries, agroecological schemes are implemented in order to reduce water quality impairment from agricultural pesticide use. However, demonstrating the success or failure of these schemes is challenging because other influencing factors can confound their effects. For instance, in-stream pesticide concentrations have been found to vary greatly due to the interannual variability in weather conditions (e.g., the timing, intensity, and duration of precipitation events) and pesticide application practices (e.g., the variability in timing and spatial application of differing pesticides that have different chemical properties).

Our current work aims to investigate the necessary conditions to detect significant trends in pesticide concentrations in the context of the Swiss National Action Plan (NAP), which aims to halve the pesticide risk from agricultural activities within Swiss river networks by 2027. We use a modelling approach to explore possibilities and limitations of the existing monitoring scheme for separating long-term effects of the NAP from interannual variability due to weather conditions. For that purpose, we use an existing model for simulating pesticide transport at the catchment scale. After calibration, we simulated 10 years of herbicide concentrations with and without (i.e., the counterfactual) an assumed 50% reduction of the pesticide applied and evaluated the resulting concentration levels.

Our results indicate that the interannual variability due to weather conditions can exceed even a 50% change in pesticide application. This implies that the concentration levels themselves are insufficient to demonstrate the effectiveness of the NAP within a reasonable time horizon of a decade. This is because the lowering of in-stream pesticide concentrations may be due to the timing and intensity of precipitation relative to the application of pesticides and not from the effectiveness of pesticide mitigation measures. Therefore, we explore ways to account for the weather effects on the pesticide concentration levels. Furthermore, we found that comparing the pesticide concentrations in years that have both above average precipitation during pesticide application periods and contain precipitation events that occur shortly after pesticide application can lead to more robust statements about the effectiveness of the mitigation measures. Preliminary double mass analyses of cumulative rainfall during the application period versus cumulative maximum concentrations suggest that significant trends can be identified with 11 years of data (6 years before NAP implementation and 5 years into it). We are currently exploring how sensitive our results are to pesticide properties, such as sorption and degradation half-lives.

How to cite: Chow, R., Sceidegger, R., Doppler, T., Dietzel, A., Fenicia, F., and Stamm, C.: Counterfactual hydrological pesticide transport modelling: Can we detect long-term in-stream pesticide trends due to mitigation?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3478, https://doi.org/10.5194/egusphere-egu2020-3478, 2020.

Pesticides high-tier, long-term environmental risk assessments (ERA) are based on the combination of complicated mechanistic models to evaluate regulatory compliance. The modeling framework often involves large sets of input factors (model parameters, initial and boundary conditions, and other model structure options). How can we identify the relative importance of human, chemical, physical and biological drivers on the assessment results? Is there a case for “the right answers for the right reasons”? For the case of pesticide mitigation practices like vegetative filter strips (VFS) for runoff mitigation, what are the important factors controlling or limiting their efficiency under different field settings? We evaluate the combination of the current ERA frameworks (US EPA PWC and EU FOCUS SWAN) in combination with VFSMOD, an established and commonly used numerical model for the analysis of runoff, sediment, and pesticide transport in VFS. We present a systematic study of the importance of different field conditions that have been proposed in the past as limiting the efficiency of VFS in realistic settings: flow concentration (channelization) through the filter, timing of pesticide application compared to other drivers, assumptions about the degradation and remobilization of pesticide trapped in the filter between runoff events, seasonal presence of a shallow water table near the receiving water body. We identify instances in which the importance commonly assigned to these factors is not supported by the mechanistic analysis, where other factors different than those proposed largely control the results of the assessments.

How to cite: Muñoz-Carpena, R., Fox, G., and Ritter, A.: Effectiveness of Vegetative Filter Strips for Mitigation in Higher-Tier Pesticide Exposure Assessments: Mechanistic Analysis with VFSMOD, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1617, https://doi.org/10.5194/egusphere-egu2020-1617, 2020.

Non-point source pollution has become the main pollution source of surface water , among which colloidal pollutants are a kind of important non-point source pollutants. Rainfall runoff is the main factor that causes non-point source pollutants to migrate to water. Vegetative filter strips is an effective measure to control non-point source pollution. Vegetative density is one of the important factors affecting pollutant removal efficiency. In order to clarify the removal efficiency of colloidal non-point source pollutants by vegetative filter strips with different densities under rainfall conditions, it is necessary to study the effects of vegetative density and rainfall intensity on the migration and removal mechanism of colloids in vegetative filter strips. Based on the numerical model established by coupling non-Darcy flow water balance equation and colloid transport equation, combined with laboratory experiments and numerical simulation, the removal mechanism of colloid at different migration distances was studied under the conditions of fixed inflow, different rainfall intensity and vegetative density.

The results show that: 1) Although there is no infiltration, the colloid diffuses from surface water into saturated sand, which increases the removal efficiency of colloid. 2) Increasing vegetative density will increase the removal efficiency of colloids in vegetative filter strips. With the increase of density, the velocity of flow decreases, which decreases the deposition capacity of colloids on vegetative and increases the diffusion of colloids from surface water to soil. 3) Under rainfall conditions, the presence of rainfall increases the removal efficiency of colloids by vegetative filter strips. Although rainfall weakens the ability of vegetative to deposit colloids, it enhances the ability of colloids to diffuse to soil. The deposition capacity of colloids on vegetative increased with the increase of rainfall intensity. 4) The interception ability of vegetative enhances the diffusion ability of colloids to soil, and enhances the removal efficiency of colloids by vegetative. 5) In the vegetative filter strips, the adsorption coefficient of colloids decreases with the migration distance, mainly due to the heterogeneity of colloids. In the process of colloid migration, the absolute value of surface potential and the colloid with smaller particle size along the course are easy to be removed by vegetative filter strips because of the smaller barrier between colloid and plant, the smaller second energy potential well and the strong adsorption capacity of colloid deposition.

The research results provide important theoretical basis and reference for designing vegetative filter strips to remove colloidal non-point source pollutants under rainfall conditions.

How to cite: Yu, C. and Sun, Y.: Effects of Rainfall and Vegetation Conditions on Colloid Transport in Saturated Vegetative Filter Strips, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3278, https://doi.org/10.5194/egusphere-egu2020-3278, 2020.

Recent efforts to tackle diffuse water pollution from agriculture (DWPA) have focussed on improving farmers’ awareness under the expectation that this would contribute to adoption of best management practices (BMPs) and result in water quality improvements. To date, however, no study has studied the full awareness-behaviour-water quality pathway; with previous studies having mostly addressed the awareness-behaviour link relying on disciplinary approaches. Here, we investigated whether awareness-focussed approaches to mitigating DWPA work, addressing the pathway in full using a multidisciplinary approach. We did this by working with Welsh Water (a utility company in the UK) on their Weed wiper project which encourages farmers to consider ‘smarter’ ways of weed, pest and disease control and promotes the safe storage, use and disposal of pesticides and thus safeguard drinking water sources. One aim of this project was to mitigate pesticide pollution in watercourses, through a free ‘weed wiper’ hire trial. The main goal of the trial was to promote farmers’ awareness and uptake of BMPs to tackle the rising concentrations of the pesticide MCPA (2-methyl-4-chlorophenoxyacetic acid) in drinking water sources in three catchments in Wales. Weed wipers are a proven and effective method of managing weeds and have multiple benefits. By wiping an herbicide directly onto weeds, weed wipers dramatically reduce spray drift in comparison to more traditional methods, such as boom or knapsack spraying. Using less chemical can save land managers money and reduce the risk to their health, water and the wider environment. Using factorial analysis of variance, we analysed MCPA concentrations from 2005 to 2019 for all water treatment works (WTWs) in the three catchments where the weed wiper trial had occurred and all the WTWs within three control catchments that had not been part of the trial but were in a similar location and of a similar characteristics. This was followed by semi-structured in-depth interviews with institutional stakeholders and farmers with varying degrees of exposure to the Weed wiper project.  Results show that MCPA concentration for both treatment and control catchments had reduced following the weed wiper trial, however, considerably larger (38.9%) decreases were observed in the treatment catchments than in the control catchments (10%) and these differences were statistically significant (p<0.05, n= 2858). Results from the stakeholder interviews suggest that the weed wiper project had contributed to changes in behaviour and that these are very likely to have resulted in the water quality improvements. Further analysis revealed, however, that other psychosocial, agronomic, catchment and climate factors also influenced farmers’ behaviour. Therefore, while awareness is an important step towards improving water quality, policymakers need to consider the role of these other variables in their interventions and how they interact with awareness. This research is the first one to cover the full awareness-behaviour-water quality pathway, and to combine different scientific disciplinary 'knowledges' with local non-scientific knowledge to explain water quality responses within the context of awareness-focussed interventions. 

How to cite: Okumah, M.: Do awareness-focussed approaches to mitigate diffuse pollution work? A study on combined behavioural and water quality evidence, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7640, https://doi.org/10.5194/egusphere-egu2020-7640, 2020.

With an exponentially growing number of micropollutants dispersed in the environment and an increasing financial effort associated with the detection of very low concentrations in water bodies, models at catchment scale have become an essential tool to identify potential hotspots, to prioritize monitoring campaigns and to support river basin management plans. The choice of the model approach generally brings with it compromises between complexity and accuracy and depends on the specific goals and needs. In this work we compare and critically discuss the performance and the suitability of two different modelling approaches applied at the mesoscale (catchments area between 9 km² and 300 km²). We present the results for two perfluorinated compounds, namely Perfluorooctanoic acid (PFOA) and Perfluorooctanesulfonic acid (PFOS). Both are well-known hazardous pollutants, but not much is known about the spatial distribution of the contamination in river basins.

The first model (MoRE, Modeling of Regionalized Emissions) is a relatively data intensive, semi-empiric tool conceived for regionalized pathway analysis. We applied it in all Austrian river catchments to estimate yearly loads and annual mean concentrations. The parametrization relied on a targeted monitoring and on composite samples across several environmental compartments (Zoboli et. al., 2019). We validated the model at 12 quality measurement stations with yearly loads and annual mean concentrations. The second tool is a fate process-based model train developed within the EU SOLUTIONS project for the Danube River Basin (Lindim et al., 2016), which we validated at the same water quality stations. The model train estimates daily concentrations based on emissions and substance properties. It requires only few regional data, mainly regarding hydrology, and thus the parametrization is much easier.

The MoRE model showed very good agreement for the loads for PFOA (NSE 0.81, mNSE 0.68) and PFOS (NSE 0.89, mNSE 0.76) and partially good agreement regarding the annual mean concentrations: PFOA (R² 0.41, NSE 0.22, mNSE 0.11) and PFOS (R² 0.8, NSE 0.73, mNSE 0.53). The SOLUTIONS model train showed a systematic overestimation of annual mean concentrations for most of the stations for PFOA (R² 0.19, NSE -5.1, mNSE -0.78) and PFOS (R² 0.61, NSE -9.5, mNSE -1.4). As our observation data consist of long-term composite samples, we were not able to compare the daily concentrations given by the model with the samples. Thus, we could not investigate the temporal pattern of the model deviation.

Despite some limitations, the comparison indicates that the higher parametrization effort required by the MoRE model yields more accurate results. Where parametrization data is available, MoRE shall be preferred, since it also provides information about the contribution of different emission pathways (e.g. groundwater and interflow, wastewater treatment plants, industry) to the total emissions. SOLUTIONS brings clear advantages when parametrization data is scarce or for very large river basins. However, it would benefit from a further refinement based on the more detailed system understanding provided by MoRE. A future line of research would thus be their parallel application in combination with a targeted monitoring able to cover both spatial and temporal variability.

How to cite: Kittlaus, S., Zoboli, O., van Gils, J., Clara, M., Gabriel, O., Hochedlinger, G., Broer, M., Krampe, J., and Zessner, M.: Fate of micropollutants at catchment scale and prediction of river concentrations. Which model to choose? A case study for perfluorinated compounds in Austria, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8722, https://doi.org/10.5194/egusphere-egu2020-8722, 2020.

Water-based microbial pathogens are often responsible for the spread of waterborne diseases in polluted coastal waters. However, difficulties in directly measuring pathogens have resulted in Faecal Indicator Bacteria (FIB) being commonly used as risk indicators in coastal and bathing water management. FIB groups, particularly those of E coli and enterococci, are easily quantified in laboratory tests and are used worldwide to assess health risks in bathing and shellfish harvesting waters.

Dublin Bay off the east coast of Ireland extends to over 300 km² and is home to species and habitats of high conservation importance. Its significant environmental, economic, cultural, recreational and tourism importance to the 300,000 people living within the Bay area and to the wider Dublin population is reflected in its 2015 Biosphere designation from the United Nations Educational, Scientific and Cultural Organisation (UNESCO). Recent years however, have seen an increase in pressures on the water quality in Dublin Bay with diffuse and point source pollution discharges from both the urban and rural catchments connected to the bay being a cause of increasing concern for the responsible authorities charged with managing the coastal waters in the context of national and European legislations, particularly the EU Bathing Water Directive (2006/7/EC).

Here we present the development of a 3-Dimensional numerical model for simulating the transport and fate of FIB (namely E.coli and Intestinal Enterococci) in the receiving waters of Dublin Bay. A dynamic decay rate, which included the effects of salinity, temperature and light intensity was adopted in the model, and was shown to offer advantages over the use of constant decay rate models for simulating the bacterial die-off. More importantly however, the analyses of sediment samples taken from the intertidal zone in the bay revealed relatively high faecal bacteria concentrations. The developed model in this study allows for the effects of sediment on bacteria transport processes in surface waters and in particular, the release of bacteria from sediments into the water column. The model was validated with measurements of current speed and direction at multiple points in Dublin Bay, and with faecal indicator bacteria concentrations (E.coli and Intestinal Enterococci) determined for neap and Spring tides in both wet and dry conditions. Results from model simulations agreed well with observed data. The model represents a high-level strategic tool that will be used to understand how water quality pressures in Dublin Bay may be altered under different climate change scenarios. The work presented forms part of the EU INTERREG funded Acclimatize project (www.acclimatize.eu/) that is investigating the longer-term water quality pressures in Dublin Bay that may arise in the context of a changing climate.

How to cite: Gao, G., Corkery, A., O’Sullivan, J., Meijer, W., O’Hare, G., Masterson, B., Reynolds, L., Martin, N., Sala-Comorera, L., and Muldoon, C.: Fate and transport modelling of faecal indicator bacteria in Dublin Bay, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11479, https://doi.org/10.5194/egusphere-egu2020-11479, 2020.

Dichloromethane (DCM) is a toxic industrial solvent frequently detected in multi-contaminated aquifers. DCM often co-occurs with chlorinated ethenes resulting in complex mixtures posing challenges to predict its fate in groundwater. Changes in hydrochemistry and redox conditions in groundwater due to fluctuations in the water table may affect the extent and pathways of pollutant biodegradation. In this context, Compound-Specific Isotope Analysis (CSIA) is a useful tool to evaluate natural degradation of halogenated hydrocarbons. In this study, the impact of water table fluctuations on DCM biodegradation was examined in two laboratory aquifers using dual-element isotope analysis - the stable isotope fractionation of two elements (e.g., ¹³C and ³⁷Cl), and high-throughput biomolecular approaches. The aquifers were supplied with contaminated groundwater from the former industrial site Thermeroil (France). High-resolution sampling and monitoring of pore water allowed examining, under steady and transient conditions, the aquifers response with respect to hydrochemistry and microbial composition. A dual C-Cl stable isotope approach (Λ^C/Cl = Δδ¹³C/Δδ³⁷Cl) was developed using GC-IRMS (C-DCM) and GC-MS (Cl-DCM) to estimate the extent of DCM degradation and to identify DCM degradation pathways. Under the experimental steady conditions, dissolved oxygen (<1.2 mg/L) and increasing Fe²⁺ concentrations at lower depths of the aquifer models indicated iron-reducing prevailing conditions, while mass transfer of oxygen increased during water table fluctuations. Pronounced carbon isotope fractionation of DCM was associated with larger DCM mass removal under transient conditions (>90%) compared to steady conditions (mass removal of 35%). Under transient conditions, carbon enrichment factors (ε_C) became larger over time ranging from -18.9 ± 3.4‰ to -33 ± 0.3‰ whereas chlorine enrichment factors (ε_Cl) remained constant (-3.6 ± 0.7‰). In contrast, a similar ε_C of -20 ± 3.5‰ (beginning of transient condition) but a larger ε_Cl of -10.8 ± 2‰ were determined under steady conditions. As Λ^C/Cl values are independent of complicating masking effects, and thus reflect reaction mechanisms, dual C-Cl isotope plots suggested distinct DCM degradation pathways under steady and transient conditions with Λ^C/Cl values of 1.68 ± 0.26 and 3.41 ± 0.50, respectively. Even though a contribution of different mechanisms may take place during transient conditions, Λ^C/Cl values fall in the range of S_N1 pathways reported for Ca. Dichloromethanomonas elyunquensis (Λ^C/Cl = 3.40 ± 0.03).  The distinct Λ^C/Cl values may imply mechanistically distinct C-Cl bond cleavage reactions subjected to microbial adaptations during dynamic hydrogeological conditions. Although bacterial communities did not significantly change over time, the occurrence of Geobacter under both steady and transient conditions supports DCM degradation under iron-reducing prevailing conditions. Altogether, our results highlight that water table fluctuations enhance DCM biodegradation and influence DCM degradation pathways compared to steady conditions. This integrative study provides new insights into in situ degradation of DCM in contaminated aquifers and accounts the effects of dynamic water tables on DCM degradation.

How to cite: Prieto Espinoza, M., Weill, S., Belfort, B., Lehmann, F., Masbou, J., Müller, E., Vuilleumier, S., and Imfeld, G.: Reactive transport of dichloromethane in laboratory aquifers: insights from dual-element isotope analysis and biomolecular approaches, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15103, https://doi.org/10.5194/egusphere-egu2020-15103, 2020.

Antibioresistance may develop in different contexts (e.g. hospitals, wastewater treatment plants, animal farming) through various processes. Because municipal landfills may have received medication waste coming from citizens but also from hospitals, they may represent a source of antibioresistance disseminating in the natural environment. Together with the fate of pharmaceuticals and endocrine disruptors, we studied the fate of antibioresistance from a former municipal landfill located in Nantes, France. Both municipal and hospital waste were deposited in this landfill between 1969 and 1987. The total volume of waste is around 2 million cubic meters.

We sampled leachates from the landfill, as well as groundwater upstream and downstream the landfill. Extraction (SPE or liquid/liquid) on frozen or fresh samples allowed quantifying 30 pharmaceutical molecules and 8 other emerging by LC/MSMS, UPLC/MSMS or GC/MSMS. The abundance of total cultivable communities was determined by counting on non-selective medium. Culture media used in clinical microbiology (drigalski / ceftazidime, Msuper CARBA and ESBL) were used to determine the proportion of the bacterial community that is resistant to antibiotics. Eventually, the diversity of the total communities was studied by PCR-TTGE and by 16S metabarcoding (MiSeq Illumina).

Over of the whole substances sought, 11 pharmaceutical molecules (not antibiotics), have been quantified in the leachates and 2 endocrine disruptors (bisphenol A and triclosan). Most substances were also recovered in groundwater immediately downstream the site (including carbamazepine) at concentrations ranging between 0.1 µg/L and 10 µg/L. The number of detected substances was lower a few hundred meters far from the landfill. More especially bisphenol A and diclofenac show lower concentrations ranging from 0.1 to 1 µg/L and about 0.1 µg/L respectively). Similar observations were shown for antibioresistance. The bacteria from leachates show a more important antibioresistance than in the other groundwater samples. The transfer of antibioresistant bacteria seems limited downstream the landfill, with nevertheless higher content at the immediate downstream. The natural attenuation may be explained by several processes, some being the same as for metals and PAH.

How to cite: Le Guern, C., Lepinay, A., Aujoulat, F., Capiaux, H., Jumas-Bilak, E., Lebeau, T., Licznar, P., Flahaut, B., Augris, P., Bodéré, G., and Béchet, B.: Fate of antibioresistance, pharmaceuticals and endocrine disruptors from a former municipal landfill, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11743, https://doi.org/10.5194/egusphere-egu2020-11743, 2020.

Sulfamethoxazole (SMX) is one of the antibiotics most commonly detected in aquatic and terrestrial environments and is still widely used, especially in low income countries. The Katari watershed encompassing the biggest city in the Altiplano and having its outlet in the Titicaca lake was studied:  ten soils having contrasting properties were collected throughout the watershed. SMX displacement experiments were carried out in repacked soil columns to explore SMX reactive transfer and to assess the contamination risk of water resources in the Bolivian Altiplano. Relevant sorption processes were identified by inverse modelling of experimental breakthrough curves. Different processes were identified depending on the soil type:  irreversible sorption, instantaneous and rate-limited reversible sorption. SMX mobility was lower in soils located upstream of the watershed (organic and acidic soils - Regosol) and was related with a higher adsorption capacity compared to the soils located downstream (lower organic carbon content - Cambisol). SMX was be classified as a moderately to highly mobile compound in the studied watershed, linked to soil properties such as pH, OC and soil texture. Sulfamethoxazole can potentially threaten the quality of surface and groundwater pollution in the lower part of the studied catchment, threatening Lake Titicaca water quality.

How to cite: Archundia Peralta, D., Duwig, C., Spadini, L., Morel, M.-C., Prado, B., Orsac, V., and Martins, J. M. F.: Sulfamethoxazole mobility and risk of contamination of water resources at the catchment scale (Katari - Titicaca Lake, Bolivia), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22128, https://doi.org/10.5194/egusphere-egu2020-22128, 2020.

The most widely implemented mitigation measure to reduce transfer of pesticides and other pollutants to surface water bodies via surface runoff are vegetative filter strips (VFS). To reliably model the reduction of surface runoff, eroded sediment and pesticide inputs into surface water by VFS in a risk assessment context, an event-based model is needed. The most commonly used dynamic, event-based model for this purpose is VFSMOD. VFSMOD simulates reduction of total inflow (ΔQ) and reduction of incoming eroded sediment load (ΔE) mechanistically. These variables are subsequently used to calculate the reduction of pesticide load by the VFS (ΔP). There are several options in VFSMOD to calculate ΔP, notably the empirical Sabbagh equation (either with original or revised regression coefficients) and a regression-free, mechanistic mass-balance approach (Reichenberger et al., 2017).

Four studies with 16 hydrological events were selected from the experimental data compiled by Reichenberger et al. (2019), representing different levels of data availability and uncertainty. A first set of VFSMOD simulations, with parameterization according to the settings in the tool SWAN-VFSMOD, was run with the aim to compare the performance of the different pesticide trapping equations.  The simulations yielded a general overestimation of ΔE, suggesting that the SWAN-VFSMOD parameterization of sediment filtration is too optimistic. However, a reliable prediction of ΔE is important for the reliability of predicted ΔP, in particular for strongly sorbing compounds.

In a second step, a maximum-likelihood-based calibration and uncertainty analysis with the DREAM-ZS algorithm was performed for each hydrological event and the target variables ΔQ and ΔE. Overall a good match of measured ΔQ and ΔE was achieved, but only a few parameters could be well constrained.

In a third step, in order to reduce the observed equifinality, the hydraulic parameters were fixed to the best parameter sets obtained during the second phase, and only sediment filtration parameters were calibrated with DREAM-ZS.

The most important parameter characterizing the incoming sediment in VFSMOD is the median particle diameter DP. A set of empirical equations to predict DP from soil texture (Foster et al., 1985) was used as supporting information in the calibration of DP.         

The poster will present an improved, generic parameterization methodology for sediment trapping in VFSMOD that can be used for regulatory VFS scenarios.

How to cite: Reichenberger, S., Sur, R., Kley, C., Sittig, S., and Multsch, S.: Improved parameterization of sediment trapping in VFSMOD, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1253, https://doi.org/10.5194/egusphere-egu2020-1253, 2020.

Vegetative filter strips (VFS) are commonly implemented in the field to mitigate runoff pesticide inputs into surface waters and protect aquatic ecosystems. The efficiency of this mitigation practice can be evaluated within the current regulatory high-tier, long-term environmental risk assessments (ERA) in combination with VFSMOD, an established and commonly used numerical model for the analysis of runoff, sediment, and pesticide transport in VFS. For every rainfall/runoff event in the long-term time series, VFSMOD takes the PRZM calculated edge-of-the-field surface runoff, eroded sediment yield, and dissolved and particle-bound pesticide load.  It then calculates infiltration, sedimentation and pesticide trapping in the VFS during the event, and the outflow into the downslope aquatic body for further calculations and risk analysis. Importantly, at the end of each event, VFSMOD calculates the amount of pesticide residue retained in the filter (sediment-bound and infiltrated in the liquid phase), its degradation until the next event in the series, and the fraction of pesticide residue that is remobilized and added to the next runoff event. In earlier VFSMOD versions, full remobilization of the pesticide residue sorbed to sediment and that dissolved in the soil surface mixing layer (typically the top 0.5-5 cm) was calculated conservatively. Recent VFSMOD ERA applications for very highly-sorbed (i.e. pyrethroids) or persistent pesticides indicate that the full remobilization scheme might be too conservative in some cases. In this work, we evaluate new alternative partial remobilization schemes in VFSMOD, i.e. no remobilization of adsorbed residues, but full remobilization of dissolved residues in the mixing layer, or alternatively just a fraction of the mixing layer by diffusive exchange with the runoff. We evaluate the effects of the alternative remobilization schemes on observed total VFS pesticide reductions from available field data. In addition, employing global sensitivity analysis, we assess the relative importance of the alternative remobilization model structures in the context of the expected field variability of other known drivers of VFS efficiency (hydrology, soils, vegetation, pesticide chemical characteristics). The study provides science-based recommendations for future high-tier pesticide ERA with VFS mitigation.

How to cite: Muñoz-Carpena, R., Reichenberger, S., and Sur, R.: Effect of Remobilization of Pesticide Residues in Vegetative Filter Strips for Mitigation in Higher-Tier Pesticide Exposure Assessments with VFSMOD, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1615, https://doi.org/10.5194/egusphere-egu2020-1615, 2020.

Transformation products (TP) of pesticides are found everywhere in the aquatic environment. Their dynamic formation and subsequent transport from agricultural fields to adjacent water bodies can be estimated by using environmental fate models, which is done e.g. in the registration process for plant protection products in the European Union. In this study, an overview of models, transformation simulation concepts and model applications for TP estimation including leaching and catchment scale models is given. The review is restricted to models which were tested against field data in peer-reviewed publications. The models included in this review are GLEAMS, MACRO, RZWQM(2), PEARL, PRZM, Pelmo, LEACHM, HYDRUS 1-D, ZIN-AgriTra and the Field Release Model (FRM).

Investigating model structures revealed, that six transformation schemes, i.e. possible transformation pathways, are implemented in the models. Only one of the reviewed models, PELMO, uses a completely flexible scheme. In all other models, pathways are restricted. An assessment of model complexity, including hydrological processes and transformation-affecting processes, resulted in PELMO having the highest transformation but the least hydrological complexity among leaching models. RZWQM is the leaching model with the highest hydrological complexity and ranks second in transformation processes. Among the three catchment scale models, ZIN-AgriTra ranks highest in both, hydrological and transformation complexity.

Even though the number of publications of TP model applications is rather low, the number of leaching models is adequate (eight models). At the catchment scale, however, only two models with proven applications exist in the literature. A spatio-temporal analysis of all models revealed a gap in catchment and regional-scale models with a daily or lower temporal resolution. Thus, well-developed and applied catchment-scale models should be extended by a TP module. This would enable scientists and authorities to estimate TP concentrations or to analyse the environmental fate of TPs at the larger catchment scale. At the same time, the fate processes in models should be updated to reflect the current state of knowledge, especially more flexible transformation schemes and the formation of TPs in different compartments (i.e. plant, soil, water). The integration of pathway prediction models such as the University of Minnesota Pathway Prediction System could enhance the assessment of the large number of pesticide TPs in the aquatic environment.

How to cite: Gassmann, M.: Modelling the transfer of pesticide transformation products from agricultural fields to the aquatic environment – state of knowledge and future challenges, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2168, https://doi.org/10.5194/egusphere-egu2020-2168, 2020.

Atrazine has been banned in Europe since 2003, but is still a widely used herbicide in the rest of the world. It presents an environmental threat due to its environmental persistence and ecotoxicity. Although soil bacteria have evolved effective biodegradation pathways, atrazine persists in soils at low concentrations making soils to potential continuous sources of groundwater pollution. Experiments using isotopologues of atrazine in simplified systems (chemostat and retentostat) indicate, that limited mass transfer across the cell membrane controls atrazine degradation at low concentrations. We extended and parameterized an existing mathematical model of atrazine degradation in the chemostat/retentostat system using laboratory data. By integrating this modeling approach into a more complex soil model, the role of mass transfer across bacterial cell membranes can be assessed against other rate limiting processes of atrazine biodegradation in soil at low concentrations.

How to cite: Chavez Rodriguez, L., Pagel, H., Streck, T., and Ingalls, B.: From Chemostat/Retentostat to Soil: Modeling bioavailability limitations on atrazine degradation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11754, https://doi.org/10.5194/egusphere-egu2020-11754, 2020.

Agricultural pesticides can enter surface waters through various pathways and impair the water quality. In the past, numerous studies have been conducted for certain entry paths such as surface runoff, direct drift into water bodies or preferential flow to drainage systems. Man-made hydraulic shortcuts (e.g. road storm drains or manholes of tile drainage systems) might potentially also play a major role for pesticide inputs into surface waters. However, they have been largely overlooked in the past. This study is the first one to measure pesticide concentrations in hydraulic shortcuts in agricultural catchments.

For our analysis, we selected a small catchment (2.8km²) with predominant arable land use in the Swiss Plateau. We installed a rain event-based sampling system at six locations in the catchment: water level proportional samplers at four road storm drainage inlets, one auto sampler in a manhole collecting water from the tile and road drainage system, and another auto sampler in the stream at the outlet of the catchment. In addition, we measured rainfall in the catchment as well as discharge or water level at each of the six sampling locations.

During spring and summer of 2019, samples were collected during 19 rain events. In a first step, the samples from the drainage inlets were analyzed. Liquid chromatography coupled to high-resolution mass spectrometry was used to quantify concentrations of 40 pesticides known to be applied in the catchment.

The obtained results support the hypothesis that hydraulic shortcuts can be relevant for pesticide transport. First, a wide variety of compounds was detected: 33 substances were found in the samples, 7 were not detected. Per rain event, 4 to 15 pesticides were measured on average. Second, some of the compounds were found in very high concentrations: some exceeded concentrations of 5 µg/L and reached up to 60 µg/L.

Ecological quality criteria are known for 15 of the analyzed substances. Based on the sum of the respective risk quotients, nearly a third of the samples posed an acute ecological risk. In most cases, the elevated risk could almost exclusively be attributed to the two herbicides Dimethenamide and Terbuthylazine, as well as to the fungicide Epoxiconazole. Azoxystrobin, Cyproconazole, Mesulfuron-methyl, Metamitron and Metribuzin added to the overall risk to a lesser extent.

In a next step, samples taken by the auto sampler will be analyzed to obtain time series of the rain events and to link the findings from storm drain inlets to the concentration dynamics observed in the receiving drainage system and the river itself.

How to cite: Dax, A., Schönenberger, U., Beck, B., Vogler, B., Singer, H., and Stamm, C.: Pesticide concentrations in hydraulic shortcuts exceed environmental quality criteria, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9507, https://doi.org/10.5194/egusphere-egu2020-9507, 2020.

Pesticides from agricultural origin may harm surface water quality and pose a risk for aquatic organisms. In Europe, the regulations on agricultural pesticide usage are currently focusing on “classical” pesticide transport pathways, such as surface runoff, spray drift into surface waters, or tile drainage flow. Recent studies have shown that in certain cases also so-called hydraulic shortcuts (e.g. road storm drains, or manholes of the tile drainage systems) can be of major importance for pesticide transport into surface waters. However, until now research has widely neglected this transport pathway.

In this study, we investigated the relevance of hydraulic shortcuts for the pesticide transport from arable land to surface waters in Switzerland. We selected twenty small catchments throughout the Swiss midlands as study areas by performing a weighted random selection on a nation-wide hydrological catchment stratification dataset. On average, they have an area of 3.5 km² with a fraction of 44 % of arable land. In the agricultural areas of these catchments, we mapped hydraulic shortcuts using different data sources: Field surveys, high-resolution aerial images captured by a fixed-wing drone as well as plans of the road storm drains and the tile drainage systems. Subsequently, we modelled the hydrological connectivity of arable areas to surface waters using a digital elevation model and a D-infinity flow direction algorithm. Within this model, we distinguished between areas with a direct and indirect (i.e. via shortcuts) surface water connectivity.

Our model results show that major fractions of the arable areas with surface water connectivity are not connected directly, but via hydraulic shortcuts: The fraction of indirectly connected areas ranges between 18 % and 90 %, with a median of 52 % for the 20 catchments. In order to check the model robustness we performed sensitivity analyses for different model parameters, such as sink filling depth, maximal flow length, or parameters addressing the influence of roads, forests, and hedges. In certain cases, changes of those model parameters have a strong influence on the absolute extent of directly and indirectly connected areas. However, their fractions compared to the total connected area were insensitive to changes in the model parameters.

In addition, we will present the results of a model predicting the fraction of arable land connected to shortcuts within a catchment, depending on auxiliary quantities (e.g. length of roads of a certain type, land use, slope). Using this model, we can estimate the arable land fraction per catchment on a national scale.

How to cite: Schönenberger, U. and Stamm, C.: What pesticide legislation forgot about: Pesticide transport through hydraulic shortcuts, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16396, https://doi.org/10.5194/egusphere-egu2020-16396, 2020.

High-quality, safe, and sufficient drinking water is essential for life: we use it for drinking, food preparation and cleaning. Agriculture is the biggest source of pesticides and nitrate pollution in European fresh waters. Pesticide occurrences in rivers result from diffuse runoff from farmland or from point sources from the farmyard. Although many best management practices (BMPs) to mitigate these diffuse and point sources are developed and widely disseminated for several years, the effective implementation of mitigation measures in practice remains limited. Therefore, the Waterprotect project has been set up to improve the knowledge and awareness of the impact of crop protection products on the water quality among the many actors, to identify the bottlenecks for implementation of suitable BMPs and further develop new governance strategies to overcome these issues for a more effective drinking water protection. As all actors share the responsibility to deal with the water quality, government agencies (e.g. environmental agencies), private actors (e.g. drinking water company, input supplier, processing industry) and civil society actors (e.g. farmers) are involved in the project. Processes to cope with the problem are initiated in 7 action labs among which the Belgian Bollaertbeek action lab. The study area is a small agricultural catchment where surface water is used as intake to produce drinking water for the nearby city. The area is sensitive to erosion and based on a physical analysis and risk analysis of the catchment, the implementation of filling and cleaning places on individual farms and buffer strips along the watercourse are proposed as suitable measures to tackle the pollution problem. In order to implement them, mechanisms to increase the involvement of targeted farmers and alternative governance systems are studied. Results of the analysis of the water quality issues and the water governance system in the Belgian Bollaertbeek action lab and the strategies to try to improve the uptake of mitigation measures to improve water quality will be presented.

How to cite: Seuntjens, P., Pauwelyn, E., Belmans, E., Joris, I., Dupon, E., Kerselaers, E., Borremans, L., Lammens, S., and Keupers, I.: Stimulating implementation of best management practices to reduce pesticide loads to surface water in a small agricultural catchment, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21802, https://doi.org/10.5194/egusphere-egu2020-21802, 2020.

The exposure assessment of plant protection products (PPP) at drinking water abstraction points is of growing interest for authorities, water suppliers, industry, and other stake holders and is hence particularly addressed in the EU regulatory framework (regulation 1107/2009). However, there is no generic guidance available on the derivation of drinking water abstraction concentrations in the EU. An exception is the national approach of the Netherlands, a simplistic but very solid first Tier approach, which considers edge-of-field PEC_sw, use intensity including cropping area within a drinking water catchment, application practice and dissipation in the water system amongst others.  The Dutch approach underlies worst-case assumptions e.g. all agricultural land is connected and releases water to a water body. Our work explores the feasibility of a general tiered EU-wide approach to derive realistic PPP concentrations at drinking water abstraction points. Specifically, our goals are: (i) the characterization of EU-wide drinking water catchments, (ii) the identification of vulnerable catchments based on agricultural area or specific crops, (iii) to enable substance specific modelling for agricultural area/crop using a landscape-level assessment model.

On this account, we analyzed the European catchments for specific crops on the basis of the Water Framework Directive (WFD). The focus was on catchment characteristics (e.g. crop area, soil hydraulic properties) which have a strong impact on runoff as well as drainage generation and therefore on the mixing of PPPs in surface water. In a first step, the spatial variation of the mixing factor by crop area was investigated taking into account the stream course from headwater catchment to a larger main river. In the second step, we identified typical abstraction areas for surface water and groundwater using proxy data (e.g. protection zones and other proxy data) with the aim to explore the most vulnerable combinations in the EU. These data can then be used for the definition of specific (vulnerable) scenarios regarding the mixing of PPPs in surface water for a specific crop on EU level.

It is expected that these data in combination with landscape-level modelling using the Soil and Water Assessment tool (SWAT) can be used as starting point for a tiered exposure assessment to derive generic mixing factors and drinking water concentrations at abstraction locations.

How to cite: Gebler, S., Schröder, T., and Li, S.: The road towards an EU-wide tiered approach assessment of pesticide concentration at drinking water abstraction locations - a combined approach of GIS analysis and modelling on catchment level, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10174, https://doi.org/10.5194/egusphere-egu2020-10174, 2020.

Biocides added to facade renders and paints prevent algae and fungi growing at conventional buildings. During rain events biocides leach from facades into the urban environment and its compartments i.e. soil, surface water and groundwater. In many cases polluted façade runoff reaches partly sealed pavements and a major part infiltrates. Transport and transformation processes of biocides below these pavements are largely unknown. It may be hypothesized that concentrated infiltration in joints surrounding paving stones may enhance water percolation and accelerate solute transport. This would mean that partly sealed pavements beneath building facades are hotspots for the entry of biocides into groundwater. This study aims at testing this hypothesis using an experimental mass balance approach.

Five weighable lysimeters in freestanding boxes represent a small-scale section of an urban environment. Three lysimeter have a sealed or partly sealed plaster surface (concrete stones, granite stones with sand joints, and grass paver). The other two lysimeter represent unsealed surfaces, one of them contains a 10cm soil layer with grass cover. The fifth lysimeter acts as a control and has a 40cm layer of filter gravel. Below all surface layers there is 20cm of crushed sand and 10cm of filter gravel. This setup follows typical guidelines of urban construction.

A hose with holes represents the linear leachate of a façade during a rain event. In pre-tests isotopically depleted (collected snowmelt) and enriched (spiked with a heavy standard) water serves to illustrate differences between areal and linear infiltration. Then Terbutryn dissolved in water acts as the main contaminant. It is a biocidal ingredient of a variety of paints and renders. Additional tracers such as bromide, uranine and sulforhodamine B help to illustrate the solute transport inside the lysimeters. Brilliant blue is used to visualize infiltration patterns.

For the experiment the boxes are saturated to field capacity. Pulses of the Terbutryn and tracer solution are poured on the gutter to represent a series of rainfall events with façade leaching. The entire percolate is collected at the bottom of the lysimeter and water samples are taken at regular intervals. After the experiment, the lysimeter matrices are sampled for Terbutryn, three prominent transformation products and for the different tracers. In parallel, physico-chemical soil properties are assessed. This experiment will provide new insights into processes that promote biocide leaching from building facades into urban groundwater.

How to cite: Linke, F. and Lange, J.: An experiment to assess the influence of urban pavements on biocide leaching from facades into urban soil and groundwater, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5336, https://doi.org/10.5194/egusphere-egu2020-5336, 2020.

Drinking water security in the UK is facing increasing pressure from rising demand, fuelled by population growth and rising periods of drought. Monitoring and regulation of water quality and related internal biogeochemical processes within drinking-water reservoirs is therefore paramount to maintaining security of supply, as well as allowing continued efficient and cost-effective management. In aquatic systems, internal biogeochemical processes are controlled by a complex set of oxygen-controlled forcing mechanisms; as diffuse pollution inputs from upstream catchments enter oxygen-dynamic reservoirs that frequently include nutrient- and metal-rich sediment, deleterious soluble chemical species (e.g., trace metals such as manganese, Mn) can be released from the sediment to the overlying water. Mn in particular is a problem for drinking water treatment plants. In light of oxygen-related water quality issues, almost all UK drinking water utilities use aeration systems to optimise oxygen concentrations and corresponding water quality and ecosystem health. 

Blagdon Lake in Somerset, SW England is one such medium-size (1.8km2), shallow depth (max: 13.1m) drinking-water reservoir underlain by Mn-rich sediments. The goal of this project was to investigate the dynamics of Mn release into the overlying water, by coupling a catchment model (SWAT) and a reservoir model (CE-QUAL-W2) together. The coupled whole-system model would be assessed using multiple atmospheric, land-use, and catchment management scenarios to discern the driving processes of Mn release and quantify risk to future water security.

An extensive five-month field campaign was undertaken in Summer 2019 to build water quality time series and calibration datasets for the reservoir model (CE-QUAL-W2). Techniques and equipment deployed during the field work included: water sample filtration & soluble/insoluble Mn analysis at 2m depth intervals; permanently installed thermistor chains using Onset TidbiT v2 loggers at 1m depth resolution; water quality profiles from an EXO3 Sonde, logging pH, chlorophyll-α, conductivity, and turbidity; and surface sediment core Mn analysis. This data was then collated with atmospheric data (ERA5), and existing datasets of nutrient concentration data at multiple inflows (inc. NO2/NO3, Ammonium, Total P/Ortho P). Initial analysis of the data collected during the field campaign suggest that periods of stratification align with elevated Mn concentrations in the water column, directly relating soluble Mn release to air temperature.

How to cite: Waterhouse, J., Kjeldsen, T., and Bryant, L.: Investigating manganese dynamics in a coupled catchment-reservoir system: Lake Blagdon – SW England , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19160, https://doi.org/10.5194/egusphere-egu2020-19160, 2020.

Groundwater contamination resulted from anthropogenic activity often proves to be a persistent feature of the affected groundwater regime. The contaminated groundwater body is a complex and dynamic entity commonly called the “contaminant plume”, it is characterized by spatially dependent concentration pattern that exhibits temporal changes. In order to assess the actual state of the plume contemporaneous sampling of all assigned monitoring wells is necessary. These contemporaneous samplings should provide compatible results, just like subsequent sampling campaigns. Differences between consecutive concentration patterns help to understand the temporal behavior of the plume.

A monitoring well provides direct contact between the water originating from of the screened aquifer and the atmosphere. The water within the well may undergo physicochemical changes, between sampling events, mainly when aquifer water movement at the screened section of the well is slow. Among diverse alterations the stagnant water within the well may be depleted in volatile components, enriched in dissolved oxygen therefore the chemistry of the stagnant water within the well is typically not representative of the aquifer water. These alterations would not confine to the water contained inside of the well casing, they will diffuse into the aquifer at the screened section. The extent of this altered zone is hard to calculate, as it depends on a number of factors. The sampling procedure should ensure that representative formation water is sampled instead of altered water.

It is well known for long that sampling procedure can affect sample integrity. Most standardized sampling procedures consist a pre-sampling purge phase to avoid the sampling of stagnant water instead of aquifer water. Most procedures aim to define the necessary extent of the purging in well volumes (from three-five to twenty volumes). The other approach is to purge the well until all or some of certain field parameters (such as pH, specific electric conductivity, temperature, dissolved oxygen, oxidation-reduction potential, turbidity) stabilize, however definitions for parameter stabilization criteria are not uniform. Parameter stabilization approach is used mostly, when low-flow sampling technique is applied. In addition to the stabilization of field parameters low-flow technique requires water level stabilization as well.

The test site is a chlorinated hydrocarbon contaminated site, the affected subsurface consists of layered sandy aquifers and silt-clay aquicludes. Three monitoring wells were repeatedly tested quarterly on five sampling occasions. Field parameters were measured in a flow through cell and recorded regulary. Three samples were taken during purging: at the beginning of the purging; after extraction of three well volumes; and when field parameters are stabilized. The samples were analysed for organic and inorganic components.

Results indicate that at wells with lower contaminant concentrations insufficient purging may result in overestimating the proportion of contaminant degradation products over primer contaminant components.

How to cite: Mathe, A. R., Kohler, A., and Kovacs, J.: Testing the relation between pre-sample purge extent, parameter stabilization and dissolved contaminant concentration at a DNAPL site, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-948, https://doi.org/10.5194/egusphere-egu2020-948, 2020.

The distributed physically-based model ECOMAG-HM was applied to simulate cycling of water and heavy metals (HM) (copper, zinc, manganese) on the surface, in soil, groundwater and river water of the Nizhnekamskoe Reservoir (NKR) watershed under various scenarios of economic activity and climate changes*. The NKR watershed is located in the South Ural region of Russia and has an area of 186000 km2. This watershed is characterized by high background concentrations of HM due to wide occurrence of ore deposits and considerable concentration of ore-parent elements in rocks. The main purpose of the study was to quantify the contribution of point (wastewater) and diffuse sources to pollution of water bodies, which is necessary for planning measures to reduce HM pollution in the watershed. The first objective of the study was to assess the ECOMAG-HM model potential for large scale modelling water quality parameters at the different hydrological and hydrochemical monitoring stations by comparing simulated and observed the hydrological and hydrochemical regimes in the historical period on the main river and its tributaries. The local areas of the catchment were identified, which were not covered by hydrochemical observations, with significant levels of river water HM contamination. The maps of simulated spatial fields of genetic components of runoff and HM washoff to the river network were designed. The contribution of anthropogenic sources to the HM runoff formation was estimated and it has been established that with the current level of anthropogenic load, the contribution of wastewater point discharges does not exceed 4%. Scenarios and consequences of increasing the amount of HM discharged as part of wastewater are considered. The time scale of the catchment self-purification from HM was evaluated. The results showed that in the absence of external impacts on the catchment area, a decrease of HM content in river waters over a 400-year period will not be exceed 10%. Climate change impact assessment on water quantity and quality was simulated for future period on the level 2050 for copper. The results are (a) the average annual river flow will increase by 11%, (b) the average annual flow of copper - by 18%, (c) the increase in copper runoff was mainly due to an increase in river runoff, (d) the change in average annual concentrations of copper in river runoff is insignificant (+7%). 
Acknowledgements. The work was financially supported by the Russian Science Foundation (grant no. 17-7730006).

*Motovilov, Yu.G., Fashchevskaya, T.B. Simulation of spatially-distributed copper pollution in a large river basin using the ECOMAG-HM model // Hydro. Sci. J., 2019, V. 64, Is. 6, pp. 739–756.

How to cite: Motovilov, Y. and Fashchevskaia, T.: Simulation of river pollution by heavy metals under different scenarios of anthropogenic load on watershed and climate changes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11171, https://doi.org/10.5194/egusphere-egu2020-11171, 2020.

Acid sulphate soils (AS soils) are in literature described as the “nastiest soils in the world” (Dent & Pons, 1995 pg.1) affecting swathes of land around the globe. The changed oxygen conditions in the soil as a result of altered ground water levels, causes a severe decrease in pH, consequently enabling metals to leach out to recipient water streams (e.g. Åström, 2001). In northern Scandinavia, several fish kills have been reported due to leaching AS soils (e.g. Hudd and Kjellmann, 2002) allowing for these areas to be the focal point of prior investigations (e.g. Nordmyr et al., 2008; Lax, 2005; Åström, 2001). However, seasonally lowered local groundwater levels caused by altered temperature and precipitation pattern in Scandinavia increases the need for additional research in southern Scandinavia. Therefore, this study investigates the impacts of AS soils on water chemistry in Halland, SW Sweden; an area previously covered by the Littorina sea. In order to estimate potential metal emissions after a period of low groundwater levels, in situ surface water sampling was conducted from smaller ditches draining an active AS soil into a nearby canal. Additional hydro-chemical parameters, such as pH, redox potential and electric conductivity were simultaneously measured in situ and groundwater data from nearby wells were retrieved. The concentrations of several metals, such as Al, Cu, Fe and V were analysed using an inductively coupled plasma mass spectrometry (ICP-MS) instrument and the total organic carbon (TOC) in the samples were determined. The results provided a clear indication of leaching acids to the surface water, through elevated concentrations of numerous metals, along with a pH of 3.82 - 6.64 in the surface water. Several metals such as Al and Mn, were highly elevated, in some cases close to 100 times higher than the background levels. No signal was found in the groundwater data retrieved, presumably due to the great difference in depth between private wells and the AS soil layer.

Sources:

Dent, D. L., & Pons, L. J. (1995). A world perspective on acid sulphate soils. Geoderma, 67(3-4), 263-276, DOI: 10.1016/0016-7061(95)00013-E.

Åström, M. (2001). The effect of acid soil leaching on trace element abundance in a medium-sized stream, W. Finland. Applied Geochemistry, 16(3), 387-396, DOI: 10.1016/S0883-2927(00)00034-2.

Hudd, R., Kjellman, J., 2002. Bad matching between hatching and acidification: a pitfall for the burbot, Lota lota, off the river Kyrönjoki, Baltic Sea. Fisheries Research 55, 153-160, DOI: 10.1016/S0165-7836(01)00303-4.

Lax, K. (2005). Stream plant chemistry as indicator of acid sulphate soils in Sweden. Agricultural and Food Science, 14(1), 83-97, DOI: 10.2137/1459606054224165.

Nordmyr, L., Åström, M., & Peltola, P. (2008). Metal pollution of estuarine sediments caused by leaching of acid sulphate soils. Estuarine, coastal and shelf science, 76(1), 141-152, DOI: 10.1016/j.ecss.2007.07.002.

How to cite: Lindgren, A. and Giese, M.: Sulphate soils and the abundance of metals in the surrounding water - a case study from Halland, SW Sweden. , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8257, https://doi.org/10.5194/egusphere-egu2020-8257, 2020.

The Great Salt Lake (GSL) in northern Utah is a key natural resource for migratory waterfowl and the local economy. The quality and quantity of water reaching the Great Salt Lake are of concern, particularly as competing interests along source rivers, such as the Bear River, seek to divert and capture more water to meet their needs. This project presents preliminary field study and aims to improve the scientific understanding of the chemical mixing taking place where freshwater rivers discharge into the Great Salt Lake. Water samples were collected in 16 locations in mixing zones between the Bear River Bay, marshes of the mouth of the Ogden River, and shallow water zones in the Great Salt Lake. Water samples were acidified with nitric acid and filtered through 0.2 micrometer filter. Field in-situ parameters: temperature, pH, ORP, dissolved oxygen, and electric conductance were measured using Troll 9500 probe and concentrations of forty elements were analyzed in ICP-MS and ICP-OES. Field in-situ measurements indicated that pH is weekly alkaline with saline waters typically being more alkaline than fresh water. Saline waters are more reducing than fresh waters. Fresh water flows were extensive in very shallow environments. Extremely shallow environments were more affected by high salinity mud deposits. The results indicate higher concentrations of heavy metals transported from the Bear River Bay to the Great Salt Lake than from the Ogden River. The pattern of elemental concentrations is complex. Fresh water fluxes penetrate shallow saline waters over relatively long distances (hundreds of meters). The depth of lake waters was predominantly less than 0.5 meter. ICP-OES measurements showed that overall Bear River samples had somewhat higher concentrations of major ions than in in the Ogden River. ICP-MS measurements indicated similar patterns between trace elements in the Bear River and in the Ogden River. Both areas have relatively higher concentrations of Al, Fe, and Mn. Concentrations of Pb, As, Se, and Hg are also relatively high. Correlation between in-situ parameters indicates complex relationship between different elements. For example more acidic conditions do not necessarily result in higher concentration of metals. Higher concentrations of metals correlate better with more reducing conditions. Concentrations of metals did increase significantly at more acidic conditions, but they typically characterized less saline waters. We will attempt hydrochemical modeling in the next phase of this research which will be verified by laboratory experiments of mixing of waters in question. This will allow controlling the parameters since natural dynamic flow systems driven by wind in a very shallow water and freshwater fluxes flowing far into saline water bodies might compromise accuracy of thermodynamic modeling.

How to cite: Matyjasik, M.: Water Chemistry in Estuaries Around Great Salt Lake, Utah, USA., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12272, https://doi.org/10.5194/egusphere-egu2020-12272, 2020.

Clean water is a precious resource and policies/programmes are implemented worldwide to protect and/or improve water quality. Faecal pollution can be a key contributor to water quality decline causing eutrophication through nutrient enrichment and also pathogenic contamination. The robust sourcing of faecal pollutants is important to be able to target the appropriate sector and to engage managers.  Biomarker technology has the potential for source confirmation, by using, for example, the biomarker suite of steroids. Steroids have been used in the differentiation of human and animal faeces; however, there is no unequivocal extraction technique regarding either suite’s analysis. Some of the methods used include: i) Soxhlet extraction, ii) Bligh and Dyer (BD) extraction, and iii) accelerated solvent extraction (ASE). The less costly and time intensive technique of ASE is particularly attractive, but a current research gap concerns further comparisons regarding ASE lipid extraction of soils/slurries compared with the more traditionally used methods of Soxhlet and BD extraction. Accordingly, a randomised complete block experiment was implemented to assess for differences between the three extraction methods, differences between the different sample types, and the interactions between these two factors. Following GC-MS, it was found that there was no significant difference between the steroid extraction method used, regardless of the type of sample used, for the quantity of each steroid extracted. It was concluded that ASE could be used confidently instead of the more established steroid extraction methods, thereby delivering time and cost savings.

How to cite: Manley, A., Collins, A., Joynes, A., Mellander, P.-E., and Jordan, P.: A comparative study of lipid extraction methods for the quantification of steroidal biomarkers within soil and cattle slurry, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17244, https://doi.org/10.5194/egusphere-egu2020-17244, 2020.

Biological communities present in the subsurface are essentially involved in processes influencing the water quality. Characterising the temporal and spatial dynamics of microbial communities is key to understand processes in place and their influence on water quality – particularly when used for drinking water production. Due to limitations in automation of sampling and detection of conventional, cultivation-based microbial methods, a fully automatic flow cytometer (FCM) was employed in combination with sampling for DNA sequencing at a water works in Berlin, where drinking water is derived from groundwater recharged via infiltration basins. The DNA sequencing enables a complete "meta genomic" analysis and taxonomic profiling including bacterial, archaea, viral, eukaryotic DNA and the identification of antibiotic resistance genes. The FCM determines the total number of bacterial cells in a water sample (total cell count, TCC), the number of cells that have lost membrane integrity (defect cell count, DCC) and allows statements about the ratio of low nucleic acid content to cells with high nucleic acid content (LNA/HNA). In this study, FCM was installed in a continuously flowing sampling line measuring surface water (basin water) and groundwater (observation and abstraction well) along a flow path for high-frequency microbial monitoring. The combination of automatic FCM with DNA sequencing aims at i) optimizing monitoring strategies, and ii) developing a (quantitative) microbial risk assessment for managed aquifer recharge systems.   

How to cite: Sprenger, C., Schwarzmüller, H., Menz, C., Throniker, O., Gnirss, R., and König, A.: Use of flow cytometry and DNA sequencing as a proxy for characterising microbial communities during managed aquifer recharge, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21877, https://doi.org/10.5194/egusphere-egu2020-21877, 2020.

Abstract:

Prevalence and provenance of antibiotic-resistant bacteria (ARB), antibiotic resistance genes (ARG) and metal concentrations were compared in river Kelani of Sri Lanka and Sabarmati and Brahmaputra of India. The prevalence of E. coli was 10-27, 267-76,600 and <50 CFU ml^-1 in aforementioned rivers, respectively. Isolated E. coli colonies were subjected to resistance test with norfloxacin (NFX), ciprofloxacin (CIP), levofloxacin (LVX), kanamycin monosulphate (KM), tetracycline (TC), and sulfamethoxazole (ST). The isolates were predominantly multi-antibiotic resistant, with greater resistance to TC and ST. Brahmaputra River showed greater resistance to all tested antibiotics. Sabarmati River showed higher resistance to TC and ST than Kelani. Genes conferring resistance to tetracyclines, sulphonamides, b-lactams and fluoroquinolones were common. ARG, gyrA, tetW, sul1 and ampC were detected in Kelani River, additionally, aac-(6’)-1b-cr, and blaTEM were detected in Brahmaputra River. In both countries, less polluted segments exhibited more copies of ARG. Faecal contamination was decoupled from percentage antibiotic resistance and metal contamination, suggesting to separate of hospital waste from domestic waste with specific guidelines.

Keywords: Antibiotic Resistance; Brahmaputra; E. coli; Kelani River; Sabarmati, Gene

How to cite: Kumar, M., Chaminda, T., Hanafi, S., Patel, A., Mazumder, P., Thakur, A., Honda, R., and Sewwandi, H.: Comparative Prevalence and Provenance of Antibiotic-Resistant Bacteria and Antibiotic Resistance Genes in Tropical Rivers of Sri Lanka and India, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22121, https://doi.org/10.5194/egusphere-egu2020-22121, 2020.