Der Einsatz von Filtern zur Reduzierung von Stickstoff- und Phosphoreinträgen aus der Landwirtschaft in die Oberflächengewässer wurde in Deutschland bisher kaum untersucht. In einem Workshop wurde der Stand der Untersuchungen von Projekten in Polen, Dänemark, Deutschland und Frankreich vorgestellt. Um das Potential dieser Maßnahmen auszuschöpfen, sind die Entwicklung von Entscheidungsunterstützungssystemen für geeignete Einsatzorte und weitere Demonstrationsprojekte unter Feldbedingungen notwendig.

The herbicide Glyphosate was detected in River Havel (Berlin, Germany) in concentrations between 0.1 and 2 µg/L (single maximum outlier: 5 µg/L). As the river indirectly acts as drinking water source for the city's 3.4 Mio inhabitants potential risks for drinking water production needed to be assessed. For this reason laboratory (sorption and degradation studies) and technical scale investigations (bank filtration and slow sand filter experiments) were carried out. Batch adsorption experiments with Glyphosate yielded a low KF of 1.89 (1/n = 0.48) for concentrations between 0.1 and 100 mg/L. Degradation experiments at 8 °C with oxygen limitation resulted in a decrease of Glyphosate concentrations in the liquid phase probably due to slow adsorption (half life: 30 days).During technical scale slow sand filter (SSF) experiments Glyphosate attenuation was 70-80% for constant inlet concentrations of 0.7, 3.5 and 11.6 µg/L, respectively. Relevant retardation of Glyphosate breakthrough was observed despite the low adsorption potential of the sandy filter substrate and the relatively high flow velocity. The VisualCXTFit model was applied with data from typical Berlin bank filtration sites to extrapolate the results to a realistic field setting and yielded sufficient attenuation within a few days of travel time. Experiments on an SSF planted with Phragmites australis and an unplanted SSF with mainly vertical flow conditions to which Glyphosate was continuously dosed showed that in the planted SSF Glyphosate retardation exceeds 54% compared to 14% retardation in the unplanted SSF. The results show that saturated subsurface passage has the potential to efficiently attenuate glyphosate, favorably with aerobic conditions, long travel times and the presence of planted riparian boundary buffer strips.

The Aquisafe project aims at mitigation of diffuse pollution from agricultural sources to protect surface water resources. The first project phase (2007-2009) focused on the review of available information and preliminary tests regarding (i) most relevant contaminants, (ii) system-analytical tools to assess sources and pathways of diffuse agricultural pollution, (iii) the potential of mitigation zones, such as wetlands or riparian buffers, to reduce diffuse agricultural pollution of surface waters and (iv) experimental setups to simulate mitigation zones under controlled conditions. The present report deals with (i), providing information on trace substances, which enter surface water predominantly via diffuse sources in rural or semi-rural environments. In particular, it provides a priority list of relevant substances to aid planning of monitoring programs at waterworks, which abstract surface water from rural watersheds, for which information on substance use is sparse. As this ranking is limited to substances for which broad data sets are available from literature, it is compared to actual screening programs in predominantly rural catchments in Brittany (France) and Indiana (USA). The literature review identified pesticides as the dominant known diffuse contaminant group in rural and semi-rural settings (section 2.1). This is confirmed for the agriculturally dominated Ic Catchment in France and Upper White River Watershed in the USA, where pesticides were found to dominate the diffuse source compounds (section 3). Seven agricultural pesticides were detected in the Ic Catchment with AMPA and atrazine being the most common compounds, detected in 54 % and 41 % of all the samples, respectively. In the White River Basin 26 of the 38 detected compounds were pesticides making them the largest group of chemicals detected. Based on literature values on pesticide detection in surface waters in Germany, France and the USA, a priority list was established in section 2.2 of this report (see Table on page vi). Only seven substances were among the 20 most relevant pesticides, both in the USA and in Europe. Accordingly, US and European substances are distinguished in the priority list. Most frequently detected substances were atrazine, metolachlor and simazine for the USA, AMPA (metabolite of glyphosate), diuron and atrazine for France and diuron, atrazine and isoproturon for Germany. The importance of atrazine in Europe is interesting, since it was already banned at the time of the monitoring, indicating the high persistency of atrazine in groundwater. In some cases in Germany, concentrations in surface waters were found to follow typical seasonal application patterns, indicating illegal use (pers. Comm.. M. Bach). Although the list of substances in the USA and in Europe differ, there is an agreement to the fact that many of the pesticides applied in agriculture find their way into surface waters. The concentrations found are often beyond 0.1 µg/L. For the EU this level already corresponds to the drinking water limit. Thus, if surface water is used for drinking water production pesticides seem to be of high relevance. In finished drinking water, frequently-used Isoproturon and Bentazon were most frequently detected in Germany and France. The importance for drinking water production is emphasized by frequent detections above 0.1 µg/L in finished drinking water in nine waterworks in the US. Regarding drinking water regulation, the thresholds in the USA are substance-specific and generally more than one magnitude higher than 0.1 µg/L. As a result threshold exceedance was mainly found for Atrazine. In terms of treatability in water works, the priority list includes the efficiency of classical treatment (flocculation, filtration, ozonation) and of powdered activated carbon (PAC), which is often added in emergency situations. Particularly problematic are triazines (such as atrazine), phenoxy-type substances (such as 2,4-D and Mecoprop) and Anilides/Anilines (such as Metolachlor and Acetochlor). The pesticides found in the screenings are in good agreement with the priority list of most problematic pesticides for the US and Europe. AMPA and atrazine, the substances detected most frequently in the Ic catchment, as well as 2,4-D and dichlorprop, which were found in high concentrations > 0.1 µg/L in one sample are all included in the Europe top 20 of the priority list. Other substances on the list may not have been found because they were not measured, because of relatively high analytical detection limits of the screening or simply because they are not used in the basin, dominated by corn and wheat cultures. In the White River Basin, atrazine, acetochlor and simazine were detected at concentrations exceeding early warning levels utilized by several states in the United States, indicating their high relevance concerning drinking water production. They are also included in the US top 20 of the priority list. The priority list is a reliable basis for potentially problematic pesticides. It can thus be used as a starting point for monitoring programs in rural catchments, where no specific information on pesticide use are available. If looking for pesticides in surface water, it is important to take times of application of regarded pesticides into consideration, as shown by strong fluctuations in atrazine concentrations in the source water of a waterworks in Indiana (Figure 12 of this report). The screening results indicate that also other contaminants than pesticides may play a role in rural catchments. In the screening in the semi-rural catchments in Indiana, twelve of the detected 38 substances were not pesticides, but belonged to other groups, such as domestic use products, manufacturing additives or gasoline hydrocarbons. Of these twelve substances, seven were only found in one of the two catchments, showing a strong catchment-specific relationship. The findings indicate that other substances than pesticides may be of local importance, though in the case study all 12 substances were at least 50-fold below human health benchmarks (if defined). We conclude that the pesticide priority list given below is a good starting point for diffuse pollution screening even though it may possibly not be sufficient if major local influences, such as factories, large roads with stormwater discharges, CSO or specific local pesticide uses are present.

The Aquisafe project aims at mitigation of diffuse pollution from agricultural sources to protect surface water resources. The first project phase (2007-2009) focused on the review of available information and preliminary tests regarding (i) most relevant contaminants, (ii) system-analytical tools to assess sources and pathways of diffuse agricultural pollution, (iii) the potential of mitigation zones, such as wetlands or riparian buffers, to reduce diffuse agricultural pollution of surface waters and (iv) experimental setups to simulate mitigation zones under controlled conditions. The present report deals with (iv) and evaluates the suitability of the technical scale experimental site at the UBA in Berlin, Marienfelde for simulating processes that impact the fate and transformation of nutrients in wetlands / riparian zones. A 3-month pilot investigation (Sep. to mid Nov. 2007) was conducted in order to assess the impact of vegetation on nitrate (NO3-) removal in slow-sand filters (SSFs) and identifying possible interference of glyphosate with N and C cycling processes in these systems. SSFs are engineered bio-reactors that can mitigate the transfer of a wide range of pollutants including nutrients and organic contaminants to water bodies. Two vertical-flow experimental SSFs (average area: 60 and 68 m2, depth: 0.8 and 1.2 m, respectively) at the UBA facilities in Berlin were used in this study: one unplanted and the other vegetated with Phragmites australis. The SSFs received water amended with nitrate (NO3-) and phosphate (PO4 -) without and with glyphosate (added for 2 weeks). Mineral N concentration at the mixing cell, SSF surface, 40 cm depth and at the SSF outlet was measured at least twice per week to calculate N removal rates. Physical water properties (pH, redox potential, temperature) and greenhouse gas emission (CO2, CH4 and N2O) were also monitored to gain insights into controlling processes. Results showed that N removal rates were several-fold higher in the vegetated than in the non-vegetated SSFs averaging 663 mg N m-2 d-1 (57 % of input) and 114 mg N m-2 d-1 (14 % of input), respectively. In both systems, most of the N removal occurred in the top 40 cm of the SSFs. Marked temporal variation in N removal rates was also detected with rates in general 3 times higher in late summer compared to mid/late autumn. In the latter period, a net release of N was observed in the non-vegetated SSF. The seasonal variation in N removal could be related to a lack of vegetation growth and thus plant N uptake, and may also reflect of the sensitivity of denitrification to climatic factors as suggested by strong (r2 > 0.77) linear relationships between weekly N removal rates and SSF water temperature. A clear impact of glyphosate addition on nitrate concentrations could not be observed. Denitrification, the process most responsible for the removal of nitrogen from waters and soils seems to be unaffected by the addition of glyphosate under the conditions in the experiment. The impact of glyphosate, if any, was probably much smaller compared to the strong influence of temperature on N dynamics in the SSFs. Difficulty of maintaining a constant concentration of glyphosate during dosing may have also contributed to this outcome. Nitrous oxide emission accounted for < 3 % of the total N removed was always lower in the vegetated (< 0.1 - 0.3 mg N2O-N m-2 d-1) than in the non-vegetated SSF (0.2 - 3.8 mg N2O-N m-2 d-1). Conversely, CH4 emission was always higher in the vegetated (range: +0.4 to +49.5 mg CH4-C m-2 d-1) than in the non-vegetated SSF (range: -2.1 to +1.32 mg CH4-C d-1). These results, in connection with much lower oxidation reduction potential readings in the vegetated filter, suggest that the reduction of N2O to N2 was important in the SSF systems and that N2 was the dominant N gas produced. Thus, N2 production must be quantified in order to establish N mass balance of SSF systems. The results show that technical-scale experiments can realistically simulate mitigation systems, while having control over contaminant loading, flow conditions and monitoring. Important lessons learnt for future applications are the following (i) Denitrifying conditions can be established in both SSF of the experimental site by adjusting to low flow conditions (0.23 m³/h) and dosing nitrate. (ii) Dosing of trace contaminants (in this case glyphosate) needs to be improved, but will remain difficult for the large amounts of water involved. The results underline the importance of measurements in the mixing cell. (iii) Since seasonal effects play an important role in mitigation zone performance, any experiments need to be done in parallel, rather than in succession to be able to compare the results.

The Aquisafe project aims at mitigation of diffuse pollution from agricultural sources to protect surface water resources. The first project phase (2007-2009) focused on the review of available information and preliminary tests regarding (i) most relevant contaminants, (ii) system-analytical tools to assess sources and pathways of diffuse agricultural pollution, (iii) the potential of mitigation zones, such as wetlands or riparian buffers, to reduce diffuse agricultural pollution of surface waters and (iv) experimental setups to simulate mitigation zones under controlled conditions. The present report deals with (ii) and aims at identifying numerical modelling tools that can assess the origin of contaminants as well as the impact of different mitigation measures regarding water quality aspects on a catchment scale. In order to test the identified modelling tool in the further course of the Aquisafe project a case study was found in Brittany (France) in agreement with Veolia Eau: the small watershed of the river Ic. Due to intensive agricultural land use the nitrate concentration exceeds the threshold for surface water used for drinking water purpose (which is the main concern of Veolia Eau). Additionally, trace contaminants (pesticides) were detected in the surface water ever since measurements have been carried out. Therefore modelling shall mainly support the water supplier in actions aiming at reducing the nitrate concentration in the surface water. An additional task could later on be the application of the model in order to assess the effectiveness of mitigation measures against trace contamination. In order to choose the most appropriate model a model comparison was carried out using a three step approach. The first step was a screening of different information sources and resulted in the identification of 44 existing models. The second step was a pre-selection according to essential criteria in order to identify models that fulfil the basic requirements for a) the Ic nitrate issue and b) the Aquisafe trace contaminant issue. In a third step a multicriteria analysis was carried out using 6 additional criteria followed by a final recommendation. The essential criteria used for the pre-selection of the models were a) the inclusion of major hydrological processes, b) the inclusion of the nitrogen cycle (for the Ic nitrate issue) or the inclusion of trace contaminants (for the Aquisafe trace contaminant issue) c) the size of catchments that can be modelled, d) the temporal and spatial resolution and e) the possibility to include management options and/or mitigation measures. For the Ic nitrate issue this resulted in the selection of the models: HBV-NP, HSPF, SWIM, SWAT, WASMOD and Mike She. For the Aquisafe trace contaminant issue only four models remained after the pre-selection process: DRIPS, HSPF, SWAT and Mike She. Additional criteria were then applied and resulted in the recommendation to use the model SWAT for further investigations in both cases due to sufficient accuracy and included processes (full hydrological model with water quality simulation (nutrients and trace contaminants) as well as a wide range of successful applications (amongst others). This report presents a wide range of models with their capabilities and limits. It contains criteria which were identified with the stakeholders in order to choose the most appropriate model. The approach presented in this report shall support the decision process of selecting a model for a certain problem regarding water quality and includes only a recommendation. The final decision on which model shall be applied, will be taken in agreement with the stakeholders Veolia Eau and Goel’Eaux.

The Aquisafe project aims at mitigation of diffuse pollution from agricultural sources to protect surface water resources. The first project phase (2007-2009) focused on the review of available information and preliminary tests regarding (i) most relevant contaminants, (ii) system-analytical tools to assess sources and pathways of diffuse agricultural pollution, (iii) the potential of mitigation zones, such as wetlands or riparian buffers, to reduce diffuse agricultural pollution of surface waters and (iv) experimental setups to simulate mitigation zones under controlled conditions.