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The European Commission asked the European Food Safety Authority (EFSA) to prepare a statement on a framework for the environmental risk assessment (ERA) of transition metals (e.g. iron and copper) used as active substances in plant protection products (PPPs). Non‐degradability, essentiality and specific conditions affecting fate and behaviour as well as their toxicity are distinctive characteristics possibly not covered in current guidance for PPPs. The proposed risk assessment framework starts with a preliminary phase, in which monitoring data on transition metals in relevant environmental compartments are provided. They deliver the metal natural background and anthropogenic residue levels to be considered in the exposure calculations. A first assessment step is then performed assuming fully bioavailable residues. Should the first step fail, refined ERA can, in principle, consider bioavailability issues; however, non‐equilibrium conditions need to be taken into account. Simple models that are fit for purpose should be employed in order to avoid unnecessary complexity. Exposure models and scenarios would need to be adapted to address environmental processes and parameters relevant to the fate and behaviour of transition metals in water, sediment and soils (e.g. speciation). All developments should follow current EFSA guidance documents. If refined approaches have been used in the risk assessment of PPPs containing metals, post‐registration monitoring and controlled long‐term studies should be conducted and assessed. Utilisation of the same transition metal in other PPPs or for other uses will lead to accumulation in environmental compartments acting as sinks. In general, it has to be considered that the prospective risk assessment of metal‐containing PPPs can only cover a defined period as there are limitations in the long‐term hazard assessment due to issues of non‐degradability. It is therefore recommended to consider these aspects in any risk management decisions and to align the ERA with the goals of other overarching legislative frameworks., This publication is linked to the following EFSA Supporting Publications article: http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2021.EN-6501/full

The Panel received a mandate from the European Commission to assess the genotoxic potential of triazine amine based on available information submitted by the applicants. Available information includes experimental genotoxicity data on triazine amine, Quantitative Structure–Activity Relationship (QSAR) analysis and read across with structurally similar compounds. Based on the overall weight of evidence, the Panel, in agreement with the cross‐cutting Working Group Genotoxicity, concluded that there is no concern for the potential of triazine amine to induce gene mutations and clastogenicity; however, the potential to induce aneugenicity was not adequately investigated. For a conclusion, an in vitro micronucleus assay performed with triazine amine would be needed.

The EFSA Panel on Plant Protection Products and their Residues was requested to establish health‐based reference values for groundwater metabolites (LM2, LM3, LM4, LM5 and LM6) of the active substance terbuthylazine based on the available evidence, unless the evidence was considered insufficient to do so. The request was accepted under the explicit circumstance that the reassessment would be made according to a different methodology than the routine methodology currently applied for the assessment of metabolites in groundwater. While for metabolites LM2, LM4 and LM5, it was concluded that the reference values for terbuthylazine are applicable, substance‐specific reference values could not be derived for metabolites LM3 and LM6. The applied threshold of toxicological concern (TTC) approach has shown that metabolites LM3 and LM6 are of potential concern for consumer health, since at least one representative groundwater leaching scenario results in exposure above the relevant threshold. Moreover, other sources of exposure to LM3 and LM6 could not be excluded with certainty. It is therefore recommended to address the specific toxicities of metabolites LM3 and LM6.

In the EU registration procedure, the assessment of the leaching to groundwater and the exposure of soil organisms as a result of the use of plant protection products is based on the use the FOCUS groundwater scenarios and the EFSA soil exposure scenarios, respectively. This user manual describes the use of the graphical user interface of the new FOCUSPEARL version, i.e. version 5.5.5, that facilitates the application of the scenarios for these assessments. In addition a description of the input and output files is given which helps the user to use the FOCUSPEARL model without the interface.

© 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority. The EFSA Panel on Plant Protection Products and their Residues reviewed the guidance on how aged sorption studies for pesticides should be conducted, analysed and used in regulatory assessment. The inclusion of aged sorption is a higher tier in the groundwater leaching assessment. The Panel based its review on a test with three substances taken from a data set provided by the European Crop Protection Association. Particular points of attention were the quality of the data provided, the proposed fitting procedure of aged sorption experiments and the proposed method for combining results obtained from aged sorption studies and lower-tier studies on degradation and adsorption. Aged sorption was a relevant process in all cases studied. The test revealed that the guidance could generally be well applied and resulted in robust and plausible results. The Panel considers the guidance suitable for use in the groundwater leaching assessment after the recommendations in this Scientific Opinion have been implemented, with the exception of the use of field data to derive aged sorption parameters. The Panel noted that the draft guidance could only be used by experienced users because there is no software tool that fully supports the work flow in the guidance document. It is therefore recommended that a user-friendly software tool be developed. Aged sorption lowered the predicted concentration in groundwater. However, because aged sorption experiments may be conducted in different soils than lower-tier degradation and adsorption experiments, it cannot be guaranteed that the higher tier predicts lower concentrations than the lower tier, while lower tiers should be more conservative than higher tiers. To mitigate this problem, the Panel recommends using all available higher- and lower-tier data in the leaching assessment. The Panel further recommends that aged sorption parameters for metabolites be derived only from metabolite-dosed studies. The formation fraction can be derived from parent-dosed degradation studies, provided that the parent and metabolite are fitted with the best-fit model, which is the double first-order in parallel model in the case of aged sorption.

GeoPEARL_NL is used as a higher tier instrument in the leaching assessment of plant protection products in the Netherlands. Because the soil organic matter contents in arable soils in the current version were too high, a new soil organic matter for the Netherlands was needed.

In the EU the risk of leaching of plant protection products is assessed according to the new regulation 1107/2009. For the assessment of this risk the FOCUS Groundwater scenarios have been developed. The PEARL model is one of the models that can be used to calculate the leaching concentration in groundwaterfor these scenarios. At the national level, the GeoPEARL model is used to assess the 90th percentile in space of the plant protection product in its area of use. In this report a description is given of all processes considered to describe the fate of the plant protection product in the plant-soil system, such as transport inthe soil matrix and in the macropore domain of the soil, transformation, volatilisation and sorption in soil, and processes at the plant canopy (volatilisation, penetration into the plant tissue and phototransformationon the plant surface). The PEARL model is integrated with the hydrological model SWAP. This report describes the most important processes to describe the hydrology of the soil system. Furthermore, the recent additions of the PEARL model for paddy rice systems, as well as those to simulate the fate ingreenhouse systems are also presented.

In the new Dutch decision tree for the evaluation of pesticide leaching to groundwater, spatially distributed soil data are used by the GeoPEARL model to calculate the 90th percentile of the spatial cumulative distribution function of the leaching concentration in the area of potential usage (SP90). Until now it was not known to what extent uncertainties in soil and pesticide properties propagate to spatially aggregated parameters like the SP90. A study was performed to quantify the uncertainties in soil and pesticide properties and to analyze their contribution to the uncertainty in SP90. First, uncertainties in the soil and pesticide properties were quantified. Next, a regular grid sample of points covering the whole of the agricultural area in the Netherlands was randomly selected. At the grid nodes, realizations from the probability distributions of the uncertain inputs were generated and used as input to a Monte Carlo uncertainty propagation analysis. The analysis showed that the uncertainty concerning the SP90 is 10 times smaller than the uncertainty about the leaching concentration at individual point locations. The parameters that contribute most to the uncertainty about the SP90 are, however, the same as the parameters that contribute most to uncertainty about the leaching concentration at individual point locations (e.g., the transformation half-life in soil and the coefficient of sorption on organic matter). Taking uncertainties in soil and pesticide properties into account further leads to a systematic increase of the predicted SP90. The important implication for pesticide regulation is that the leaching concentration is systematically underestimated when these uncertainties are ignored.

BACKGROUND: For the registration of pesticides in the European Union, model simulations for worst-case scenarios are used to demonstrate that leaching concentrations to groundwater do not exceed a critical threshold. A worst-case scenario is a combination of soil and climate properties for which predicted leaching concentrations are higher than a certain percentile of the spatial concentration distribution within a region. The derivation of scenarios is complicated by uncertainty about soil and pesticide fate parameters. As the ranking of climate and soil property combinations according to predicted leaching concentrations is different for different pesticides, the worst-case scenario for one pesticide may misrepresent the worst case for another pesticide, which leads to ‘scenario uncertainty’. RESULTS: Pesticide fate parameter uncertainty led to higher concentrations in the higher percentiles of spatial concentration distributions, especially for distributions in smaller and more homogeneous regions. The effect of pesticide fate parameter uncertainty on the spatial concentration distribution was small when compared with the uncertainty of local concentration predictions and with the scenario uncertainty. CONCLUSION: Uncertainty in pesticide fate parametersand scenario uncertainty can be accounted for using higher percentiles of spatial concentration distributions and considering a range of pesticides for the scenario selection. c � 2010 Society of Chemical Industry

GeoPEARL is a spatially distributed model describing the fate of pesticides in the soil–plant system. It calculates the drainage of pesticides to local surface waters and the leaching into groundwater. GeoPEARL plays an important role in the evaluation of Dutch pesticide policy plans. This study analysed how uncertainties in soil and pesticide properties propagate through GeoPEARL for three representative pesticides. The GeoPEARL output considered is the 90th percentile of the spatial distribution of the temporal median of the leaching concentration (P90). The uncertain pesticide properties are the coefficient of sorption on organic matter and the half-life of transformation in soil. Both were assumed uncorrelated in space and were represented by lognormal probability distributions. Uncertain soil properties considered were horizon thickness, texture, organic matter content, hydraulic conductivity and the water retention characteristic. Probability distributions were derived from meta-data stored in the Dutch soil information system. A regular grid sample of 258 points covering the agricultural area in the Netherlands was randomly selected. At the grid nodes, realizations from the probability distributions of uncertain inputs were generated and used as input to a Monte Carlo uncertainty propagation analysis. The results show large uncertainties in P90, with interquartile ranges larger than the median for all three pesticides. Taking input uncertainty into account also leads to a systematic shift of the P90 towards greater values. Stochastic sensitivity analysis showed that the pesticide half-life is the main source of uncertainty and that the coefficient of sorption to organic matter and uncertainty in soil organic matter contribute to a lesser extent. Uncertainty contributions from other soil properties were negligible. These results suggest that improved assessment of soil properties will only marginally improve the accuracy of the predicted pesticide leaching. Instead, more accurate assessment of the pesticide properties, in particular the pesticide half-life, is required. This is, however, difficult, because the pesticide half-life depends on highly variable soil microbial properties in a way that is as yet poorly understood.

We analysed different approaches to process oil information when simulating pesticide leaching to groundwater at the regional scale. The first approach, calculate alone (CA), consisted of the model application on point data followed by the aggregation of the results to the regional scale. Two further approaches were used to generate spatial output and differed by interpolating after or before the model run on point support (calculate first, interpolate later; CI vs. interpolate first, calculate later; IC). The three approaches were tested with both a linear (modified Attenuation Factor, AF; Rao, P., Homby, A., Jessup, R., 1985. Indices for taking the potential for pesticide contaminatio of groundwater. Soil and Crop Science Scoiety of Florida Proceedings 44, 1-8) and a non-linear (GeoPEARL; Tiktak, A., de Nie, D., van der Linden, T., Kruijne, R., 2002. Modelling the leaching and drainage of pesticides in the Netherlands: The GeoPEARL model. Agronomie 22, 373-387; Tiktak, A., van der Linden, A., Boesten, J., 2003. The GeoPEARL model. Model description, applications and manual. RIVM report 716601007) leaching model. The non-linearity of GeoPEARL appeared to produce differences between CI and IC that did not occur in the linear model. The results also suggested that the relevance of either CI or IC is dependent on the available input information. Finally, different ways to estimate the prediction precision of the three approaches are discussed. (c) 2006 Elsevier B.V. All rights reserved.

Contamination of the groundwater is an important side-effect of the usage of plant protection products in agriculture. Today, the use of plant protection products that potentially contaminate the groundwater is banned by registration procedures at both the European level (Council Directive 91/414/EEC), and the level of individual member states. The Directive places great importance on the use of models to calculate Predicted Environmental Concentrations (PECs) as a basis for assessing the environmental risks. In the first tier of the current procedure, point scale leaching models are combined with a limited number of worst-case scenarios to assess PEC groundwater in Europe. An alternative procedure would be to use spatially distributed leaching models. Such models provide policy makers with a wealth of additional information, allowing identification of high and low risk areas in terms of spatially varying environmental and land use properties. In this study, such a spatially distributed leaching model, the EuroPEARL model, was implemented to assess the leaching risk of plant protection products at the Pan-European scale. This model is one of the products that has been delivered within the framework of the APECOP project (FP5-QLK-1999-01238), which is a European project supporting the harmonised registration of plant protection products in Europe. Simulations were performed for 1062 unique combinations of Soil Mapping Unit, Climate Zone and Country. Soil properties, including soil horizon designations, were obtained from the Soil Profile Analytical Database of Europe. Daily weather data were obtained from the MARS database. Other data like irrigation data, crop data and product properties have been compiled from various sources, such as inventories, field-studies and the literature. The 1062 unique combinations together represent 75% of the total agricultural area of the European Union. Austria, Sweden and Finland could not be included in the simulations, because there was insufficient soil 2 profile information for these countries. Results are presented with a resolution of 10 x 10 km(2), which is the highest justifiable resolution based on the EU soil map 1: 1,000,000. The Pan-European results confirm that the predicted leaching concentration generally increases with precipitation and irrigation and decreases with increasing organic matter content. Because of the strong sensitivity of the leaching concentration to soil properties, there is a strong variability of the calculated leaching concentration at relatively short distances. Results further indicate that due to large irrigation amounts combined with large temporal variation of rainfall in the Southern European countries, the trend in the calculated leaching risks from North to South was less than expected. This implies that areas of high leaching risk ('hotspots') as assessed by means of the EuroPEARL model occur in all countries of the European Union, including the Southern European countries. (C) 2003 Elsevier B.V. All rights reserved.

The Netherlands has to cope with large losses of N and P to groundwater and surface water. Agriculture is the dominant source of these nutrients, particularly with reference to nutrient excretion due to intensive animal husbandry in combination with fertilizer use. The Dutch government has recently launched a stricter eutrophication abatement policy to comply with the EC nitrate directive. The Dutch consensus model for N and P emission to groundwater and surface water (STONE) has been developed to evaluate the environmental benefits of abatement plans. Due to the possibly severe socioeconomic consequences of eutrophication abatement plans, it is of utmost importance that the model is thoroughly validated. Because STONE is applied on a nationwide scale, the model validation has also been carried out on this scale. For this purpose the model outputs were compared with lumped results from monitoring networks in the upper groundwater and in surface waters. About 13,000 recent point source observations of nitrate in the upper groundwater were available, along with several hundreds of observations showing N and P in local surface water systems. Comparison of observations from the different spatial scales available showed the issue of scale to be important. Scale issues will be addressed in the next stages of the validation study.

De aanwezigheid van bestrijdingsmiddelen in het grondwater introduceert een risico voor de volksgezondheid en ecosystemen. Om deze reden zijn schattingen nodig van de uitspoeling van bestrijdingsmiddelen naar het ondiepe grondwater. Hiervoor wordt een regionaal model van het gedrag van bestrijdingsmiddelen in de grond (GEOPESTRAS) in combinatie met het informatiesysteem bestrijdingsmiddelen (ISBEST) gebruikt. ISBEST levert gegevens over het gebruik van bestrijdingsmiddelen per gemeente. Berekeningen met GEOPESTRAS werden uitgevoerd voor unieke combinaties van bodemtype (textuur en organische-stofgehalte), grondwatertrap, landgebruik en klimaat. De invoer voor PESTRAS werd via vertaalfuncties afgeleid en een ruimtelijk beeld van de uitspoeling werd verkregen door de resultaten van de individuele berekeningen te combineren met geografische informatie. Het aantal combinaties waarvoor het model moest worden toegepast bedroeg 897. Het berekende ruimtelijk beeld van uitspoeling was sterk afhankelijk van het type bestrijdingsmiddel. Bestrijdingsmiddelen die een gemiddeld gedrag wat betreft afbraak en sorptie vertonen (bijvoorbeeld atrazin), zijn sterk afhankelijk van het organische-stofgehalte. Mobiele stoffen (bentazon en hydroxy-chloorthalonil) vertonen een sterke correlatie met de textuurkaart, terwijl de uitspoeling van vluchtige stoffen (dichloorpropeen) sterk afhankelijk is van de diepte van het grondwater en bodemfysische eigenschappen. In het algemeen werd berekend dat bestrijdingsmiddelen in veengronden niet of nauwelijks uitspoelden. De hoogste concentraties werden gevonden in zand- en leemgronden met een laag organisch-stofgehalte (concentratie vaak boven 1 mug L-1). De grootste hoeveelheden bestrijdingsmiddelen spoelden uit in de Veenkolonien, de Noord-Oost Polder, het bloembollengebied en de zandgronden van Noord-Brabant. De totale uitspoeling bedroeg in 1993 ongeveer 51000 kg, waarvan 27000 kg in het diepe grondwater en 24000 kg in het oppervlaktewater terechtkwam.

Schattingen zijn nodig van de gevoeligheid van de Nederlandse bodems voor pesticide uitspoeling naar het grondwater. De belangrijkste processen die de uitspoeling van deze stoffen beinvloeden zijn omzetting, sorptie, opname en transport. Aangezien de interactie tussen deze processen complex en niet-lineair is, zijn dynamische, proces georienteerde simulatie modellen onmisbaar bij het maken van deze voorspellingen. Het model moet voldoen aan de volgende eisen: (i) modulaire opzet waardoor de model ontwikkeling en het onderhoud beheersbaar blijft, (ii) het model moet eenvoudig te koppelen zijn aan een GIS, (iii) het model moet toepasbaar zijn voor alle belangrijke combinaties van bodemtype, gewastype en pesticiden en (iv) het model moet aan hoge kwaliteitseisen m.b.t. ontwerp, documentatie, validatie en beheer voldoen. In dit kader is het model PESTRAS ontwikkeld. Dit model is opgebouwd uit bestaande submodellen, n.l. het bodemwater transportmodel SWIF, het warmte transport submodel van ILWAS en het pesticide transport- en accumulatiemodel PESTLA. Alle submodellen werden aangepast, zodat deze voldoen aan de vier boven vermelde eisen. Dit rapport beschrijft de model formuleringen, het numerieke schema en geeft richtlijnen m.b.t. de toepassing van het model (installatie, invoer en verwerking van de uitvoer). Verder geeft het rapport voorbeelden van model uitvoer en worden de resultaten van een gevoeligheids analyse beschreven. The regionalisatie en de afleiding van de data worden in een apart rapport beschreven.

Het rapport dient te worden gebruikt in combinatie met rapport 601450019, dat de nieuwe beslisboom beschrijft.

Zie ook rapport 716601008

Het Landelijk Grondwatermodel (LGM) en een een-dimensionaal model van de hydrologie van de onverzadigde zone (SWAP) zijn gekoppeld. Met dit gecombineerde model kunnen de waterstromen in het bodem- en grondwatersysteem, alsmede de stromingen vanuit het grondwater naar het oppervlaktewater, berekend worden. Het model kan zodoende de hydrologische invoer leveren voor studies naar de belasting van grond- en oppervlaktewater met nutrienten en gewasbeschermingsmiddelen. Een andere mogelijke toepassing van het model is de voorspelling van de variatie van de grondwaterstand in de tijd. Om de seizoensdynamiek correct te kunnen berekenen, worden zowel LGM als SWAP dynamisch toegepast. Het model kan op verschillende schalen worden toegepast. De prestaties van het model zijn getoetst in een studie in het Beerze Reusel gebied. In het algemeen bleek dat de overeenkomst tussen de gemiddelde diepte van het grondwaterpeil, zoals berekend met SWAP, goed overeenkwam met de gemiddelde diepte van het grondwaterpeil, zoals berekend met LGM. Het bleek echter ook dat de seizoensdynamiek onderschat werd door LGM. Nadere studie leerde dat dit veroorzaakt werd doordat de zogenaamde freatische bergingscoefficient onjuist van SWAP naar LGM werd overgedragen. Nadat dit hersteld was, was er een nagenoeg perfecte overeenkomst tussen de grondwaterstand berekend door SWAP en de grondwaterstand berekend door LGM. Een aanvullende studie moet aantonen in hoeverre de berekende grondwaterpeilen overeenkomen met de gemeten grondwaterpeilen. Deze studie moet aangeven of het gecombineerde model de hydrologische basis kan leveren voor verdrogingstudies en waterkwaliteitsberekeningen, zoals door het Milieu- en Natuurplanbureau worden uitgevoerd.

Schattingen van de emissie van bestrijdingsmiddelen van de bodem naar de atmosfeer en van de bodem naar het bovenste grondwater zijn nodig ter ondersteuning van het Nederlandse milieubeleid. Het gedrag van bestrijdingsmiddelen in de bodem is afhankelijk van diverse processen, zoals (bio)degradatie, de uitwisseling tussen de gas-, water- en vaste fasen, het transport van het middel in de bodem en de opname door het gewas. Aangezien deze processen afhankelijk zijn van o.a. meteorologische condities, is het gebruik van dynamische simulatiemodellen noodzakelijk. Om deze reden is het model PESTRAS ontwikkeld. Dit model is opgebouwd uit bestaande modellen: het hydrologisch-model SWIF, het warmtetransportmodel HEATRAS, een deel van het bestrijdingsmiddelenmodel PESTLA en het gastransportmodel GAS. Dit rapport beschrijft de koppeling van het model GAS met de versie van PESTRAS die in RIVM-rapport 715501003 is beschreven. Het rapport geeft een samenvatting van de theorie, het numerieke schema, en de modelverificatie. De gevoeligheid van het model voor de belangrijkste invoerparameters wordt toegelicht aan de hand van een aantal voorbeelden. Het rapport gaat vooral in op het gedrag van 1,3-dichloorpropeen (een grondontsmettingsmiddel). In een aanhangsel is een volledige gebruiksaanwijzing opgenomen. Op dit moment wordt het model op geregelde basis gebruikt ten behoeve van de evaluatie van de toestand van het milieu in het kader van de jaarlijkse MilieuBalans. Daarnaast speelt het model een belangrijke rol in de toelating van bestrijdingsmiddelen. Door de inbouw van het gastransportmodel kan PESTRAS nu toegepast worden voor vluchtige bestrijdingsmiddelen (Henry-coefficient > 10 exp. -5 m3 m-3).

The leaching of a substance is influenced by its physico-chemical characteristics as well as environmental conditions. In spatially distributed modelling the influence of soil properties on the half-life and the sorption constant of the substance might become important and can be taken into account. The GeoPEARL model includes options to account for sorption and transformation being dependent on soil characteristics. Using some of these options in calculations for a herbicide with both sorption and transformation dependent on the pH of the soil, the calculated leaching from an application in spring appeared to be higher than anticipated from calculations according to the so-called paired parameter approach, in which the leaching is assessed for pairs of sorption and transformation parameters at regular pH intervals. The reason for the higher leaching was that the most critical leaching conditions were not covered by the selected pH values. A ‘paired approach’ might however be useful as a first tier assessment of the leaching potential. The maximum leaching is expected with the highest DegT 50 / K om ratio, which might be obtained from plotting this ratio against the characteristic soil property. The leaching potential of the parent was more important for the leaching of the metabolite than the leaching potential of the metabolite itself. This should be accounted for in the evaluation procedure.

In a study aimed at assessing the impact of historical and future solute leaching into saturated groundwater, the quasi-three-dimensional RIVM groundwater model, LGM (version 2), was used for calculating pathlines, travel times and concentration breakthrough curves at 165 groundwater abstraction locations in the sandy soil areas of the Netherlands. The future concentration variations were assessed for nitrate and three pesticides (atrazine, bentazone and 1,2-dichloropropane). This study was carried out in the framework of the Dutch government's long-term planning for industrial and drinking-water supply. The assessment was carried out for 76 phreatic and 89 semi-confined abstraction sites on the basis of the 1988 maximum-permitted abstraction rates. Three economic scenarios were used for generating solute leaching into saturated groundwater for the scenario years 2000 and 2020. The nitrate leaching flux was simulated by a combination of methods, including the NLOAD model for agricultural land. The pesticide leaching flux was simulated by means of the GEOPESTRAS model. Subsequently, LGM was applied to calculate the concentrations at the abstraction wells, using the concentrations in the leaching flux as input. LGM is a numerical model (based on the finite-element method), comprising complex geohydrological system components. LGM uses spatially variable (heterogeneous) data for four aquifers, covering the entire surface area of the Netherlands. The concentration breakthrough curves were calculated with the module LGMCAM, based on forward pathline tracking in saturated groundwater. The processes used in LGMCAM were advection and full mixing in well screens. Neither denitrification nor degradation of pesticides in saturated groundwater were taken into account. The results are presented (1) as concentration maps for the 165 abstraction sites for 2020 and 2050 and (2) by means of time-based concentration bar charts (1950-2050) for the totalized abstraction rate for phreatic and semi-confined abstraction sites. For a number of abstraction sites a comparison has also been made between calculated and observed breakthrough concentrations. The calculated concentrations can be concluded to be a worst-case outcome. Finally, recommendations for future improvements of the method are given.

The STONE model for nitrogen and phosphorus emission to the groundwater and surface waters has been developed to evaluate the environmental consequences of policies regarding manure and agriculture. In 2000, an advisory body ('The Spiertz Commission') explicitly asked for validation of the Dutch eutrophication models. This report summarises the most important findings of the so-called 'STONE test'. STONE results were compared with monitoring data at different spatial scales from the field scale up to the national scale. At the field scale, conclusions were drawn on process descriptions and temporal dynamics. At the national scale, spatial patterns and frequency distributions were investigated. Here, STONE slightly underestimated the median nitrate concentrations in the upper groundwater. Also, the correlation between measured and simulated concentrations of nitrogen in the groundwater was good. Large differences were, however, found at the regional scale. These differences might be attributed to errors in the manure transport and application module. This suggests that STONE is not yet suitable for applications at the regional scale. The predicted concentration of nitrate and phosphorus in drain water was higher than the actual concentration of these compounds in surface waters. This was expected, because riparian retention and loss processes in surface waters were not modelled. Future research should be directed towards (i) improving the model performance at the regional scale, and (ii) further validation of the surface water component of STONE by combining the model with a surface water model.

The Dutch decision tree on leaching from soil has been re-designed to be more in line with EU guidelines on the assessment of the leaching potential of substances. The new decision tree explicitly defines reasonable worst-case conditions as the 90th percentile of the area to which a substance is applied. The tree also determines whether the median annual leaching concentration over a period of 20, 40 or 60 years complies with the EU-drinking water limit, with the length of the period depending on the application frequency. The FOCUS Kremsmnster scenario, officially adopted in the Netherlands as the national scenario, is, in the first tier, used to identify substances with a negligible leaching risk, which can then be registered without further assessment. The core of the decision tree is the second tier, in which the spatially distributed model, GeoPEARL, is used to calculate the leaching. The third tier considers the water-saturated zone up to a depth of 10 m below soil surface. As this tier did not need an update, the new approach is expected to have very little influence on the number of registered substances. Comparing the new approach with the old, we found the new first tier to be almost as strict as the old one, at least when the safety factor of 100 was not used, as in the old tree. For substances for which the leaching concentration was calculated at around 0,1 ug dm-3 using the old procedure, GeoPEARL yielded results that were approximately 10 times higher. This difference was mainly due to the annual application of the substances in the new procedure.

To support EU policy, indicators of pesticide leaching at the European level are required. For this reason, a metamodel of the spatially distributed European pesticide leaching model EuroPEARL was developed. EuroPEARL considers transient flow and solute transport and assumes Freundlich adsorption, first-order degradation and passive plant uptake of pesticides. Physical parameters are depth dependent while (bio)-chemical parameters are depth, temperature, and moisture dependent. The metamodel is based on an analytical expression that describes the mass fraction of pesticide leached. The metamodel ignores vertical parameter variations and assumes steady flow. The calibration dataset was generated with EuroPEARL and consisted of approximately 60 000 simulations done for 56 pesticides with different half-lives and partitioning coefficients. The target variable was the 80th percentile of the annual average leaching concentration at 1-m depth from a time series of 20 yr. The metamodel explains over 90% of the variation of the original model with only four independent spatial attributes. These parameters are available in European soil and climate databases, so that the calibrated metamodel could be applied to generate maps of the predicted leaching concentration in the European Union. Maps generated with the metamodel showed a good similarity with the maps obtained with EuroPEARL, which was confirmed by means of quantitative performance indicators.

STONE is ontwikkeld om landsdekkend voor Nederland de effecten van bemesting en mestbeleid op de emissies van stikstof en fosfaat uit de landbouw naar grond- en oppervlaktewater te verkennen. De nadruk in de hier gerapporteerde plausibiliteitsstudie ligt op vaststelling van de geloofwaardigheid, het realiteitsgehalte, van getalswaarden en ruimtelijke verdeling van data in STONE versie 2.0.

A one-dimensional pesticide leaching model, PEARL, in combination with a geographical information system was used to calculate the leaching potential of pesticides into local surface waters and the regional groundwater. Calculations were performed for6405 plots, which are unique combinations of spatially distributed model inputs. To have the seepage and drainage fluxes correctly described, the model was loosely coupled with a regional groundwater model. Simulations were carried out for four pesticides with different properties. Results showed that, generally, the average fluxes of pesticide into local surface waters were higher than the average fluxes of pesticide into the regional groundwater. Discharge by rapid drainage mechanisms (i.e. tube drainage and surface drainage) dominated. For the four pesticides, different spatial patterns of leaching and discharge by drainage water were predicted. It was shown that the spatial pattern was affected by a large number of interacting processes, and that the relative importance of these processes differed between the four example pesticides. This should be kept in mind when applying the USES system, which describes the leaching of pesticides on the basis of a limited number of pesticide parameters. Frequency distributions of the leaching concentration were compared with results from the first tier of the Dutch pesticide registration procedure, which comes down to the application of a single standard scenario. For two pesticides, the first tier was not strict enough. It was shown that it is not possible to find one single standard scenario, which applies to the full range of registered pesticides. This means that the number of standard scenarios should be increased. Direct application of a regional-scalemodel, however, is to be preferred, because it provides the user with frequency distributions and gives information about areas of safe usage.

The Pesticide Transport Assessment model (PESTRAS) is a process-oriented model to simulate the fate and movement of water and pesticides in a cropped field soil. The model was evaluated using field data for bromide, ethoprophos and bentazone, collected from a field experiment in a humic sandy soil near Vredepeel, the Netherlands. Model predictions were generally within the 95% confidence intervals of the observations when site-specific model inputs were used. If generic parameter values were used, the model predictions sometimes deviated strongly from the observed data. This was especially true for pesticide degradation properties. The bromide simulations showed that preferential flow was not an important process for this field soil. A significant fraction of the applied ethoprophos disappeared by surface volatilization. The downward movement of this pesticide was slightly overestimated, due to not considering sorption kinetics. The depth-dependence of pesticide transformation was atypical: an important fraction of the applied bentazone was transformed under micro-aerobic to anaerobic conditions in the subsoil.

The sensitivity of pesticide leaching and accumulation to variations in pesticide properties, soil temperatures, soil water fluxes, and transport parameters was investigated with the general solute transport model, SOTRAS. Pesticide interactions include non-linear Freundlich equilibrium sorption, temperature and pressure head dependent first-order transformation kinetics, and plant uptake. For a number of pesticides with different mobility and half-lives, Monte Carlo simulations were carried out with Latin Hypercube Samples in a preset range of the input parameter domain. The sensitivity of model inputs to model outputs was quantified by statistics of linear regression. The time evolution of model sensitivity and the contribution of various model inputs to the total sensitivity were quantified as well. The standardized analysis gives rapid quantitative information about model behaviour. The results from the analysis are used to determine which parameters should be measured in greater detail and which need further calibration. Results are also used to set up sampling strategies. In general, the accumulation of pesticides in the plough layer was very sensitive to model inputs influencing the transformation rate of the pesticide (soil temperature and half-life) and almost insensitive to sorption characteristics and soil water fluxes. Only in the case of very persistent and mobile pesticides, accumulation was most sensitive to soil water fluxes. The concentration of pesticide in ground water was most sensitive to the Freundlich concentration exponent, and, to a lesser extent, to the Freundlich coefficient, except for some pesticides which are hardly sorbed. The leaching of these pesticides was most sensitive to half-life and soil temperature. The linear regression model could not be used for pesticides with high sorption coefficients, even if variation of the input was kept as low as 1%, but good results were obtained after logarithmic data transformation.

Dutch nutrient policies for agriculture are generally implementations of European environmental Directives, i.e. the Nitrates Directive (ND), the Water Framework Directive (WFD) and the National Emission Ceilings Directive (NECD). We present an evaluation of these policies with respect to target achievement, effectiveness, costs and benefits. Implementation of the Nitrates Directive decreased nutrient surpluses and improved groundwater quality. However, the nitrate target of 50 mg/l was still exceeded in groundwater in half of the sand region. Ecological quality of surface waters improved slightly, but this improvement was mainly due to measures for the WFD and not to reduced nutrient losses from agriculture. The NECD reduced emissions of ammonia effectively, but critical loads of nitrogen were still exceeded in the majority of ecosystems. Health benefits of reducing the concentrations of ammonia aerosols were however substantial. Overall, nutrient policies have generated net benefits for Dutch society: Annual costs were estimated to be 500 million euros and societal benefits were estimated to be between 900 and 3700 million euros. With policies currently in place, the general protection goals of the Directives will not be met. Reaching more targets in a cost-effective way would first require better coordination of policies to implement the three Directives. For example 65% of phosphorus input to surface waters is caused by agriculture but the Dutch implementation of the WFD hardly contains any measures to reduce nutrient loads from agricultural soils. In addition to more strict national policies that are better enforced, regionally differentiated mitigation options would be needed. The most robust option would be mining of soil phosphorus by zero P-application in agricultural soils that affect sensitive aquatic ecosystems. Where target achievement cannot be combined with competitive agriculture, political choices would have to be made between ecology and agriculture, or for financial compensation of affected farmers. A key factor for implementation would be redistributing of costs and benefits between specific groups of farmers or regions. This would imply better integration of the Common Agricultural Policy with environmental directives.