volV) (0123456789().,-volV) can move into the groundwater specified in the exposure assessment option as well as the magnitude of residues in groundwater. The objective may also include determining degradation rates in soil as a function of depth, persistence and movement of residues in groundwater, efficacy of mitigation measures, or confirmation of more detailed studies on a wider range of sites. Sampling schedules should consider the expected time required for an active substance to move through the soil into groundwater, as well as expected persistence in both soil and groundwater. Movement and persistence can be affected by both site characteristics and properties of the active substance and its metabolites. The need to tailor study designs to objectives, exposure assessment options, compound properties and site characteristics complicates the development of standardised study designs. Therefore, this report includes a number of example designs.Other key points that must be addressed by study designs are the vulnerability of the chosen sites compared to the vulnerability of all use areas supported by the study, the product use before and during the study, and the connectivity of the sampled groundwater to treated fields. Demonstrating connectivity (a quality criterion in the EU assessment of monitoring sites to exclude false negative measurements) is more challenging for catchment or aquifer monitoring compared to shallow wells installed as part of in-field or edge-of-field studies. This report includes an extensive discussion on assessing vulnerability of monitoring sites. This includes information on different approaches to vulnerability assessment and mapping as well as for setting monitoring sites into context. Lists of available methods and data sources available at the European level are also included. In addition to information on study design and estimating vulnerability, this report includes information on a number of other topics: avoiding contamination during sampling and/or analysis, avoiding influencing residue movement as a result of purging during sampling, and proper study documentation (Good Laboratory Practices and/or quality criteria). Procedures that are discussed include site selection (new or existing wells), installation of monitoring wells, sample collection, and analysis of samples. The report also provides information on causes of outliers (abnormally high concentrations not the result of normal leaching through soil), the use of public monitoring data, information on further hydrological characterisation (such as use of tracers, groundwater age dating, and geophysical methods), and information that should be included in reports providing results of groundwater studies. AbstractGroundwater monitoring is recommended as a higher-tier option in the regulatory groundwater assessment of crop protection products in the European Union. However, to date little guidance has been provided on the study designs. The SETAC EMAG-Pest GW group (a mixture of regulatory, academic, and industry scien...

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The study of mechanisms controlling preferential flow and transport in variably saturated fractured clayey till is often hindered by insufficient spatial resolution or unknown measuring volume. With the objective to study these mechanisms while circumventing the obstacles, tracer experiments with two fluorescent tracers Acid Yellow 7 (AY7) and Sulforhodamine B (SB) were performed at three different rain events for a fall and a summer season. Irrigated areas were excavated down to depths of 2.8 m and the movement of both tracers in the exposed profiles was delineated simultaneously by high spatial resolution apparent concentration maps (pixel approximately 1 mm(2)) obtained with an imaging device. The device consists of a light source and a CCD camera, both equipped with tracer-specific-filters for fluorescent light. The fluorescence images were corrected for nonuniform lighting, changing surface roughness, and varying optical properties of the soil profile. The resulting two-dimensional apparent concentration distribution profiles of the tracers showed that: (i) relative low water content in the upper 10 cm of the irrigated till in summer had a pronounced retardation effect on the AY7-migration and no effect on the SB-migration; (ii) the dead-end biopores were not activated in the fall season; (iii) only 3D fracture-plans connected to hydraulically active 1D-biopores contributed to the leaching; (iv) the tracer migration primary followed macropores during both seasons, though AY7 also followed a topsoil piston transport in summer; (v) the highest tracer pixel apparent concentrations were often found in macropores and most pronounced in the summer season; and (vi) 3D-dilution in fractures seems to play a dominating role in AY7-migration in the fall season.

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Abstract. The application of nitrogen (N) fertilisers to crops grown on tile-drained fields is required to sustain most modern crop production, but it poses a risk to the aquatic environment since tile drains facilitate rapid transport pathways with no significant reduction in nitrate. To maintain the water quality of the aquatic environment and the provision of food from highly efficient agriculture in line with the EU's Water Framework Directive and Nitrates Directive, field-scale knowledge is essential for introducing water management actions on-field or off-field and producing an optimal differentiated N-regulation in future. This study strives to provide such knowledge by evaluating on 11 years of nitrate-N concentration measurements in drainage from three subsurfacedrained clayey till fields (1.3-2.3 ha) representing approximately 71 % of the surface sediments in Denmark dominated by clay. The fields differ in their inherent hydrogeological field settings (e.g. soil-type, geology, climate, drainage and groundwater table) and the agricultural management of the fields (e.g. crop type, type of N fertilisers and agricultural practices). The evaluation revealed three types of clayey till fields characterised by: (i) low net precipitation, high concentration of nitrate-N, and short-term low intensity drainage at air temperatures often below 5 • C; (ii) medium net precipitation, medium concentration of nitrate-N, and short-term medium-intensity drainage at air temperatures often above 5 • C; and (iii) high net precipitation, low concentration of nitrate-N and long-term high intensity drainage at air temperatures above 5 • C. For each type, on-field water management actions, such as the selection of crop types and introduction of catch crops, appeared relevant, whereas offfield actions only seemed relevant for the latter two field types given the temperature-dependent reduction potential of nitrate off-field. This initial well-documented field-scale knowledge from fields that are representative of large areas in Denmark is a first step towards establishing a differentiated N-regulation for clayey till areas. Additionally, it provides a unique starting point by identifying important parameters for future mapping of catchment-scale variations in nitrate concentrations and fluxes.