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Het bepalen van afbraaksnelheden van gewasbeschermingsmiddelen in water onder realistische omstandigheden is belangrijk voor een correcte bepaling van blootstellingsconcentraties in de toelating. Om te beslissen of het zinvol is een software instrument te ontwikkelen om derden in staat te stellen hogere- trede, realistische afbraaksnelheden in water op een geautomatiseerde, relatief eenvoudige wijze af te leiden, heeft een inventarisatie plaatsgevonden. Ten eerste, om inzicht te verkrijgen in hoe vaak geschikte aquatische cosm studies in de buitenlucht beschikbaar zijn in registratie dossiers, en ten tweede, hoe vaak hogere-trede afbraaksnelheden gebruikt zijn in de toelatingsprocedure op EU, zonaal, of nationaal niveau. Voor 21 stoffen is informatie over aquatische cosm studies in de buitenlucht gevonden in de Europese stofbeoordelingsdossiers of nationale produktbeoordelingen. Voor 15 stoffen waren er voldoende metingen in water en sediment als functie van tijd en in gespecificeerde water- en sedimentlagen beschikbaar om een hogere-trede afbraaksnelheid te kunnen bepalen. Nadere beschouwing van de conclusie op de geaccordeerde Lijst van EindPunten van de Europese Autoriteit voor Voedselveiligheid, laat zien dat er voor geen van de 21 stoffen hogere-trede afbraaksnelheden in water zijn gebruikt op EU niveau. In de nationale, Nederlandse toelatingsprocedure voor gewasbeschermingsmiddelen zijn hogere-trede afbraaksnelheden gebruikt voor drie stoffen over de afgelopen 21 jaren. Hogere-trede afbraaksnelheden worden dus relatief weinig toegepast. Daar ontwikkeling en onderhoud van een software instrument om hogere-trede afbraaksnelheden geautomatiseerd te bepalen een substantiële inspanning vergt, bevelen wij niet aan om een dergelijk instrument nu te ontwikkelen. In het tweede deel van dit rapport wordt daarom een kort richtsnoer gegeven voor de schaarse gevallen dat het wel zinvol is een hogere-trede afbraaksnelheid in water af te leiden voor de toelatingsprocedure e

A new exposure assessment methodology for various tree crops and application methods was developed by Wageningen UR and PBL Netherlands Environmental Assessment Agency. In addition to the scenario for upward and sideways spraying in fruit orchards, which was published in 2021, this report describes the methodology for upward and sideways spraying in avenue tree nurseries and downward spraying in such nurseries and in fruit orchards. The new procedure calculates the exposure concentration based on a statistical distribution of the exposure concentration in all relevant Dutch watercourses. The methodology results in a so-called 90th percentile exposure concentration considering all watercourses alongside fruit orchards or avenue tree nurseries. The methodology accounts for the exposure by plant protection products through spray drift, drainage and atmospheric deposition. The scenarios include drift-reducing application techniques and crop-free buffer zones. With the scenarios in this report and the report on upward and sideways applications in fruit orchards, a more realistic exposure assessment is possible for edge-of-field watercourses next to fruit orchards and avenue tree nurseries regarding both upward & sideways applications and downward applications in the Netherlands., Dit rapport beschrijft een methodiek voor blootstellingsbeoordeling van waterorganismen in waterlopen na toepassing van gewasbeschermingsmiddelen in fruitboomgaarden en laanboomkwekerijen. Het is een combinatie van drie afzonderlijke onderzoeken naar blootstellingsbeoordeling, namelijk voor opwaartse en zijwaartse toepassingen in laanboomkwekerijen, neerwaartse toepassingen in deze kwekerijen en neerwaartse toepassingen in fruitboomgaarden.

The TOXSWA model has been extended with the functionality to simulate pesticide volatilization from open water surfaces on the basis of a micro-meteorological framework. TOXSWA simulates the fate of pesticides in water bodies to calculate exposure concentrations for aquatic organisms or sediment-dwelling organisms as part of the aquatic risk assessment in the regulatory process of pesticides at EU level and in The Netherlands. Volatilization of pesticides from water to air has been described in the TOXSWA model based on the Liss and Slater method. This report describes the implementation in TOXSWA of an improved methodology to describe volatilization of pesticides from small water bodies. Hourly meteorological data on wind speed and air temperature are used to calculate the rate of volatilization of the pesticide from the water layer., Het TOXSWA model beschrijft het gedrag van gewasbeschermingsmiddelen in het water-sediment systeem in kleine oppervlaktewateren. Het berekent hier blootstellingsconcentraties voor water- en sedimentorganismen, die in de aquatische toelatingsprocedure in Nederland en de EU worden gebruikt. Het model is nu verbeterd door de toevoeging van een functionaliteit voor vervluchtiging op basis van een micro- meteorologische benadering. De vervluchtiging wordt bepaald door het concentratie verschil op het atmosfeer-water grensvlak en hangt verder af van twee atmosferische weerstanden en een aquatische weerstand tegen transport van het gewasbeschermingsmiddel in de gasfase. De parameterisatie gebruikt uurlijkse waarden voor windsnelheid en temperatuur in water en in atmosfeer. Vervluchtiging van gewasbeschermingsmiddel is een belangrijk proces voor de blootstellingsconcentratieberekening. Vooral in stilstaand oppervlaktewater of water met lage stroomsnelheden kan de combinatie van langzame vervluchtiging, lage omzetting en herhaald toepassen leiden tot accumulatie van het middel in water en/of sediment en mogelijk verhoogde risico’s voor de organismen.

The current Dutch authorisation procedure for calculating the exposure of aquatic organisms to plant protection products needs to be revised. For this reason, Wageningen UR, RIVM and PBL Netherlands Environmental Assessment Agency were asked to develop a new exposure assessment methodology for various crops and application methods. This report describes the methodology for upward and sideways spraying in Dutch fruit crops. In contrast to the current procedure, the new procedure calculates the exposure concentration based on a statistical distribution of the exposure concentration in all relevant Dutch watercourses. The methodology results in a so-called 90th percentile exposure concentration considering all watercourses alongside fields grown with fruit crops. The new methodology takes input of plant protection products by spray drift, drainage and atmospheric deposition into account. Agronomic practices in Dutch apple and pear orchards were considered representative for all (high) pome and stone fruit orchard crops in the Netherlands. An important part of the new methodology is the option to mitigate spray drift deposition by using drift-reducing technologies in a higher spray drift reducing class or by including a wider crop-free buffer zone.

Estimation of the degradation rate of plant protection products in water under realistic conditions may be important for correct estimation of exposure concentrations for regulatory purposes. Standardized tests for degradation in water and in water-sediment systems in the laboratory exist, but these do not reflect degradation under field conditions. This is especially true for studies on photolytic degradation; therefore, generally photolytic degradation is not accounted for in the lower tiers of the exposure assessment. The aim of this study is to develop a procedure for the estimation of photochemical degradation rates from outdoor cosm experiments for use in the higher tiers of the exposure assessment. Observations in outdoor ponds or cosms are regularly used as a higher-tier risk assessment to evaluate the ecotoxicological effects on the aquatic ecosystem in a more realistic way. By means of inverse modelling of the behaviour of the compound in the cosm we determined the degradation rate in water, DegT50, for three compounds which are known to degrade photolytically. We did so by coupling the fate model TOXSWA to the optimisation tool PEST and determined the DegT50 for a daily reference UV radiation, weighed with a vitamin-D action spectrum, assuming that the degradation rate was directly proportional to the amount of weighed UV radiation. The UV radiation data were derived from satellite-based observations accounting for the effects of the thickness of the ozone layer and the cloud cover. For cosm studies with metribuzin, imidacloprid and metamitron we obtained satisfactory estimates of DegT50 values. After correcting these for effects of water depth, coverage of water surface by plants and the skyview factor on the UV radiation in the water, the variation between the DegT50 values of metribuzin and imidacloprid was smaller than the variation between DegT50 values derived (in an earlier study) by assuming that the degradation rate depended on water temperature, Het bepalen van afbraaksnelheden van gewasbeschermingsmiddelen in water onder realistische omstandigheden kan belangrijk zijn voor een correcte bepaling van blootstellingsconcentraties in de toelating. Er zijn standaard laboratorium testen voor afbraak in water en in water-sediment systemen, maar deze weerspiegelen niet de afbraak onder realistische omstandigheden in het veld. Dit geldt m.n. voor studies over fotochemische afbraak; dit is de reden dat fotochemische afbraak in het algemeen niet wordt meegenomen in de lagere treden van de blootstellingsbepaling. Het doel van deze studie is om een procedure te ontwikkelen voor de bepaling van fotochemische afbraaksnelheden met behulp van cosm experimenten in de buitenlucht, voor gebruik in de hogere treden van de blootstellingsbepaling. Waarnemingen in vijvers of cosms in de buitenlucht worden regelmatig gebruikt als hogere trede in de risicobeoordeling om ecotoxicologische effecten op het aquatisch ecosysteem op een realistischere manier te bepalen. Met behulp van een inverse modellering van het gedrag van een middel in de cosm hebben we de afbraaksnelheid in water, DegT50, bepaald voor drie middelen, waarvan het bekend is dat ze fotochemisch afbreken. Dit deden we door het model TOXSWA te koppelen aan het optimalisatie instrument PEST en de DegT50 te bepalen voor een dagelijkse referentie UV stralingsdosis, gewogen voor het vitamine D actiespectrum; hierbij werd aangenomen dat de afbraaksnelheid recht evenredig is met de gewogen UV straling. De UV stralingsdata waren afgeleid uit satelliet waarnemingen die rekening hielden met de dikte van de ozonlaag en de bewolkingsgraad. Voor de cosm studies met metribuzin, imidacloprid en metamitron verkregen we zo toereikend geschatte DegT50 waarden. Na een correctie voor de effecten van waterdiepte, bedekkingsgraad van het wateroppervlak door planten en de ‘hemelzicht’ factor op de UV straling in het water, was de variatie in DegT50 waarden van metribuzin en imidacloprid kleine

The European Commission asked EFSA to undertake a ‘repair action’ of the FOCUS surface water report after the EFSA Pesticide Steering Network had been consulted. The main request was to introduce into all FOCUS surface water scenarios (both run‐off and drainage) a 20‐year assessment period instead of the current 12‐ or 16‐month assessment period. Because of the 20‐year assessment period, the way application dates are defined needed to be reviewed, reconsidering the functionality of the pesticide application timing currently used. Guidance on how substance parameters should be handled when correlated with soil properties has been provided. Foliar wash‐off calculated in MACRO and Pesticide Root Zone Model was aligned and the appropriateness of including rotational crop aspects was discussed. Processing time and how to use the results of the exposure assessment were considered.

The FOCUS_TOXSWA model calculates exposure concentrations of pesticides and their metabolites in watercourses and ponds, of the so-called FOCUS surface water scenarios. These concentrations are used in the pesticide registration procedure at EU level. The model concepts of TOXSWA are described briefly. The procedure for using the TOXSWA kernel (i.e. expert use) and related input files and output files are described. Concerning FOCUS_TOXSWA, the use of the graphical user interface to access the input and output is described. Input data are stored in a database. Pesticide entries resulting from drainage or runoff/erosion are accessed from separate files generated by FOCUS_MACRO and FOCUS_PRZM. Substance properties are accessed from the SPIN tool/database. Instructions for simulating a water-sediment study and a multi-year run are given.

A methodology is presented to assess the exposure of aquatic organisms resulting from pesticide applications by sideways and upward spraying in Dutch fruit crops. It is the intention that this methodology will be used in Dutch pesticide registration. The methodology is based on the principle that the endpoint concentration represents a 90th percentile of the statistical population of concentrations to be expected in ditches alongside fruit crops. Furthermore the methodology is founded on the principle that the user should be able to choose between different drift-reduction technology (DRT) classes and between different widths of the crop-free buffer zone. Spray drift is the only exposure route considered in the methodology. The 90th percentile concentration (PEC90) is based on a spatially distributed model that simulates the frequency distribution of the annual maximum concentration of more than 70,000 spatial units (i.e. ditches characterised by waterbody properties and their orientation with respect to the direction of the rows of the fruit trees and to the N-E-S-W direction) for 100 simulation years. This frequency distribution was calculated for different application patterns, different DRT classes and different widths of the crop-free buffer zone. Next, one of the 70,000 spatial units was selected which fulfilled the criterion that it could be used to calculate this PEC90 for all combinations of application patterns, DRT classes and widths by selecting a suitable percentile of its temporal distribution of concentrations. The TOXSWA model (coupled to the hydrological SWQN model simulating water depths and water flow rates) was parameterised for this selected spatial unit to run for 26 years. The first six years were used as a ‘warming-up’ period and the remaining 20 years for assessing the required temporal percentile. The scenario ditch was 300 m long of which only the 100 m in the middle received a drift load of pesticide. The direction of water flow may chang, Dit rapport geeft een overzicht van een recent ontwikkelde methodiek voor blootstelling van waterorganismen in waterlopen na toepassing van gewasbeschermingsmiddeldn via zijwaarts en opwaarts spuiten in de Nederlandse fruitteelt.

Following a request from EFSA, the Panel on Plant Protection Products and their Residues developed an opinion on the science to support the potential development of a risk assessment scheme of plant protection products for amphibians and reptiles. The coverage of the risk to amphibians and reptiles by current risk assessments for other vertebrate groups was investigated. Available test methods and exposure models were reviewed with regard to their applicability to amphibians and reptiles. Proposals were made for specific protection goals aiming to protect important ecosystem services and taking into consideration the regulatory framework and existing protection goals for other vertebrates. Uncertainties, knowledge gaps and research needs were highlighted.

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 fro

TOXSWA simuleert het gedrag van stoffen in oppervlaktewater om blootstellingsconcentratie te berekenen voor organismen die in water of sediment leven, als onderdeel van de aquatische risicobeoordeling van gewasbeschermingsmiddelen (GBM). Het vernieuwde concept voor de beschrijving van de temperatuur in het TOXSWA model werd getest aan de hand van een bestaande implementatie van het 1D bulk model.

Realistic values for the degradation rates of pesticides in surface water are important for thew aquatic risk assessment, that is mandatory before pesticides are admitted authorised. Standardised first-tier laboratory tests exist, but the degradation rates derived from these tests do not reflect the degradation rates in the environment. Outdoor ponds or cosms are often used as a higher-tier risk assessment to evaluate the ecotoxicological effects in a more realistic way.

The TOXSWA model has been extended with the functionality to simulate hydrolysis and biotic transformation in water. TOXSWA simulates the fate of pesticides in water bodies to calculate exposure calculations for aquatic organisms or sediment-dwelling organisms as part of the aquatic risk assessment of pesticides. Hydrolysis and biotic transformation are modelled as first-order processes, occuring in the water phase only. The hydrolysis transformation rates are considered to be dependent on both pH and temperature. The biotic transformation rate is considered to be temperature-dependent only.

Following a request from EFSA, the Panel on Plant Protection Products and their Residues developed an opinion on the science behind the risk assessment of plant protection products for in-soil organisms. The current risk assessment scheme is reviewed, taking into account new regulatory frameworks and scientific developments. Proposals are made for specific protection goals for in-soil organisms being key drivers for relevant ecosystem services in agricultural landscapes such as nutrient cycling, soil structure, pest control and biodiversity. Considering the time-scales and biological processes related to the dispersal of the majority of in-soil organisms compared to terrestrial non-target arthropods living above soil, the Panel proposes that in-soil environmental risk assessments are made at in- and off-field scale considering field boundary levels. A new testing strategy which takes into account the relevant exposure routes for in-soil organisms and the potential direct and indirect effects is proposed. In order to address species recovery and long-term impacts of PPPs, the use of population models is also proposed.

In 2013, EFSA published a comprehensive systematic review of epidemiological studies published from 2006 to 2012 investigating the association between pesticide exposure and many health outcomes. Despite the considerable amount of epidemiological information available, the quality of much of this evidence was rather low and many limitations likely affect the results so firm conclusions cannot be drawn. Studies that do not meet the ‘recognised standards’ mentioned in the Regulation (EU) No 1107/2009 are thus not suited for risk assessment. In this Scientific Opinion, the EFSA Panel on Plant Protection Products and their residues (PPR Panel) was requested to assess the methodological limitations of pesticide epidemiology studies and found that poor exposure characterisation primarily defined the major limitation. Frequent use of case–control studies as opposed to prospective studies was considered another limitation. Inadequate definition or deficiencies in health outcomes need to be avoided and reporting of findings could be improved in some cases. The PPR Panel proposed recommendations on how to improve the quality and reliability of pesticide epidemiology studies to overcome these limitations and to facilitate an appropriate use for risk assessment. The Panel recommended the conduct of systematic reviews and meta‐analysis, where appropriate, of pesticide observational studies as useful methodology to understand the potential hazards of pesticides, exposure scenarios and methods for assessing exposure, exposure–response characterisation and risk characterisation. Finally, the PPR Panel proposed a methodological approach to integrate and weight multiple lines of evidence, including epidemiological data, for pesticide risk assessment. Biological plausibility can contribute to establishing causation.

In 2013, EFSA published a literature review on epidemiological studies linking exposure to pesticides and human health outcome. As a follow up, the EFSA Panel on Plant Protection Products and their residues (PPR Panel) was requested to investigate the plausible involvement of pesticide exposure as a risk factor for Parkinson's disease (PD) and childhood leukaemia (CHL). A systematic literature review on PD and CHL and mode of actions for pesticides was published by EFSA in 2016 and used as background documentation. The Panel used the Adverse Outcome Pathway (AOP) conceptual framework to define the biological plausibility in relation to epidemiological studies by means of identification of specific symptoms of the diseases as AO. The AOP combines multiple information and provides knowledge of biological pathways, highlights species differences and similarities, identifies research needs and supports regulatory decisions. In this context, the AOP approach could help in organising the available experimental knowledge to assess biological plausibility by describing the link between a molecular initiating event (MIE) and the AO through a series of biologically plausible and essential key events (KEs). As the AOP is chemically agnostic, tool chemical compounds were selected to empirically support the response and temporal concordance of the key event relationships (KERs). Three qualitative and one putative AOP were developed by the Panel using the results obtained. The Panel supports the use of the AOP framework to scientifically and transparently explore the biological plausibility of the association between pesticide exposure and human health outcomes, identify data gaps, define a tailored testing strategy and suggests an AOP's informed Integrated Approach for Testing and Assessment (IATA).

Van vijf sloten verspreid liggend over Nederland, zijn de sediment eigenschappen droge bulkdichtheid, organische-stofgehalte en porositeit zijn als functie van de diepte gemeten. Het betreft hier akkerbouw- en tuinbouwgebieden. De gevonden waarden verschillen duidelijk van de gebruikte waarden voor sediment in de oppervlaktewater scenario’s, die momenteel worden ontwikkeld voor de Nederlandse registratieprocedure voor gewasbeschermingsmiddelen (die zijn overgenomen van de EU-FOCUS scenario’s).

In the Pesticide Risk Reduction Programme Ethiopia the evaluation of risks of pesticides present in drinking water for man and cattle was selected as a priority protection goal. In cooperation with the Plant Health Regulatory Department of the Ministry of Agriculture of Ethiopia and other Ethiopian stakeholders Alterra developed a procedure to assess the risks for drinking water caused by pesticides, used according to Good Agricultural Practices (GAP). To do so, ‘realistic worst case’ scenarios were developed, that intend to protect man and cattle in 99% of all possible situations in Ethiopia. For groundwater three scenarios representing wells in aquifers in the Ethiopian highlands or Rift Valley margins were developed and for surface water three scenarios representing small rivers in the highlands or temporay stagnant ponds were developed. The scenarios were linked to crops on which pesticides are used that score high on acute, chronic or local chronic risk for man. In addition other agro-environmental conditions were defined, such as precipitation, soil, and land use management. The groundwater scenarios were parameterised in the EuroPEARL metamodel to calculate leaching concentrations to groundwater, whereas the surface water scenarios make use of the runoff model PRZM, the EU-FOCUS spray drift deposition table and the surface water model TOXSWA to calculate the concentration in the small river or pond scenarios

SWASH (Surface WAter Scenarios Help) assists the user in calculating pesticide exposure concentration in the EU FOCUS surface water scenarios. It is part of the exposure calculation procedure, being part of the obligatory evaluation procedure to place an active substance on List 1 according to EU Directive 91/414/EEC. SWASH encompasses: (i) FOCUS Drift Calculator, calculating pesticide entries through spray drift deposition, (ii) PRZM-3, calculating pesticide entries through run-off, (iii) MACRO, calculating pesticide entries through drainage and (iv) TOXSWA, calculating the behaviour of pesticides in small surface waters. It is linked to SPIN, a pesticide properties tool, and prepares input for the PRZM, MACRO and TOXSWA models. Via the SWASH shell the user can enter the shells of the other models to perform the PRZM or MACRO model runs needed to assess the fate of the substance in he FOCUS water body systems using TOXSWA.

The user-friendly shell SWASH, acronym for Surface WAter Scenarios Help, assists the user in calculating pesticide exposure concentrations in the EU FOCUS surface water scenarios. SWASH encompasses five separate tools and models: (i) FOCUS Drift Calculator, calculating pesticide entries through spray drift deposition, (ii) PRZM-3, calculating pesticide entries through run-off, (iii) MACRO, calculating pesticide entries through drainage, (iv) TOXSWA, calculating the behaviour of pesticides in small surface waters, and (v) SPIN is a central database for storage and editing of pesticide properties. The SWASH database contains information on projects and runs created by the user. This report gives a detailed description of the necessary flow of data between the various models, to make them communicate smoothly with each other. It also specifies the installation requirements for the MACRO, PRZM and TOXSWA models. The MACRO model uses an MS-Access database to store its substance and run information, while PRZM makes use of separate data files. TOXSWA uses the central SWASH database. After completing a SWASH session the user should manually perform simulations with the three individual models

Het TOXSWA model is uitgebreid met de beschrijving van vorming en omzetting van metabolieten in water en sediment. Op EU niveau wordt TOXSWA gebruikt in de aquatische risico beoordelingsmethodiek van bestrijdingsmiddelen om blootstellingsconcentraties te berekenen in de diverse water typen van de zogenaamde EU-FOCUS oppervlaktewater scenario’s. Voor de scenario’s met FOCUS riviertjes is er een bovenstrooms stroomgebied van 100 ha waarvan 20 ha met bestrijdingsmiddel is behandeld. Bij deze scenario’s willen we rekening houden met metabolieten die in het stroomgebied zijn gevormd. Daarom is een procedure ontwikkeld om de metaboliet concentraties en fluxen te corrigeren voor de FOCUS riviertjes, gevoed door het gedeeltelijk behandelde stroomgebied. De correctiefactoren van de procedure kunnen op twee manieren worden bepaald: (i) een simpele manier, waarbij de correctiefactor een functie is van de omzettingssnelheid van de moederstof en (ii) een meer gedetailleerde manier waarbij de correctiefactor een functie is van de omzettingssnelheid van zowel de moederstof als van de metaboliet, alsmede van de verblijftijd van de moederstof in het bovenstroomse stroomgebied.

The FOCUS_TOXSWA model calculates exposure concentrations of pesticides and their metabolites in watercourses and ponds. These concentrations are used in the pesticide registration procedure at EU level. The model concepts of TOXSWA are described briefly. The input files, output files, and the use of the graphical user interface to access the input and output are described. Input data are stored in a database. Pesticide entries resulting from drainage or runoff/erosion are accessed from separate files generated by FOCUS_MACRO and FOCUS_PRZM. Substance properties are accessed from the SPIN tool/database. Instructions for simulating a water-sediment study and a multi-year run are given

The degradation rate of plant protection products and their transformation products in surface water and sediment may influence their concentrations in Dutch surface water. Therefore the estimation of these rates may be an important part of the assessment of the exposure of aquatic organisms. We propose a stepped sequence of studies for estimating the rate in water going from simple and conservative to more sophisticated and more realistic studies. The sequence includes: - studies on hydrolysis and photolysis; - studies with fresh surface water in the dark; - water-sediment studies in the dark or in light; - studies with algae and macrophytes; - outdoor studies in realistic surface water systems. The usefulness of these studies for the exposure assessment in Dutch surface water is discussed.

Within the frame work of the Sino-Dutch Pesticide Environment Risk Assessment Project (PERAP) and as part of the Chinese environmental ris assessment procedures models and scenarions were developed to estimate concentrations of Plant Protection Product (PPP) leaching to the groundwater and to estimate PPP concentrations in Chinese small surface waters. Protection goals considering groundwater and surface water were defined in detail. Realistic worst-case groundwater scenario's and surface water scenarios were defined to be used in respectively a Tier 1 leaching assessment of PPP a Tier 1 assesment of the risks of PPP to aquatic ecosystems in China. Data on soil, weather, crops, irrigation and Agricultural practices were gathered for both scenario definitions. Existing models PEARL and TOXSWA were modified and parameterised for the scenarions defined.

SWASH (Surface WAter Scenarios Help) assists the user in calculating pesticide exposure concentration in the EU FOCUS surface water scenarios. It is part of the exposure calculation procedure, being part of the obligatory evaluation procedure to place an active substance on List 1 according to EU Directive 91/414/EEC. SWASH encompasses: (i) FOCUS Drift Calculator, calculating pesticide entries through spray drift deposition, (ii) PRZM-3, calculating pesticide entries through run-off, (iii) MACRO, calculating pesticide entries through drainage and (iv) TOXSWA, calculating the behaviour of pesticides in small surface waters. It is linked to SPIN, a pesticide properties tool, and prepares input for the PRZM, MACRO and TOXSWA models. Via the SWASH shell the user can enter the shells of the other models to perform the PRZM or MACRO model runs needed to assess the fate of the substance in he FOCUS water body systems using TOXSWA.

In the TOXSWA (TOXic substances in Surface WAters) model volatilization of pesticides from surface water is computed because it may be an important component of the mass balance of pesticides in water bodies. Here, we briefly review the physics of air-water gas exchange relevant in this context. A new parameterization of volatilization is proposed. This new TOXSWA parameterization would take into account key physical aspects of the air-water gas exchange process, while still fitting into the TOXSWA philosophy. It is recommended to cast the new parameterization into a micrometeorological framework, based on two atmospheric resistances and one aqueous resistance against gas transport. In this context, the dimensionless Henry coefficient is a crucial characteristic of the pesticides and determines whether atmospheric properties as modelled by the atmospheric resistances exert the main dynamic control on air-water gas exchange or the aqueous properties and resistance. Most pesticides will be subject to atmospherically controlled volatilization.

In the current Dutch authorisation procedure for calculating the exposure of surface water organisms to plant protection products, drift deposition is considered to be the only source for exposure of surface water organisms. Although drift can still be considered the most important source, atmospheric deposition and drainage may constitute important sources as well. Therefore, RIVM, PBL, Wageningen UR and the Board for the authorisation of plant protection products and biocides have derived a new procedure in which these two potential sources are included. The new procedure, described in this report, is restricted to downward spray applications in field crops

We study non-stationary flow in open discharge channels. A model is derived from basic principles, conservation of mass and momentum, which is solved numerically for the cross sectional area and discharge as a function of time and position along the channel. The model describes the effect of external inflow from fields adjacent to the channel. Several scenarios are calculated, both for very slowly, and more rapidly flowing water courses.

This report aims to give a general description of transformation processes for future use in the TOXSWA model. Hydrolysis, photolysis and biotic transformation are described as distinct processes, employing separate rate constants. Additionally, a way to introduce into TOXSWA the daily variation of pH and temperature is proposed.

We study stationary flow in open discharge channels. A model is derived from basic principles, which is solved numerically for the water level and discharge as a function of position along the channel. The model describes the effect of external inflow from fields adjacent to the channel. Several scenarios are calculated, both for very slowly, and more rapidly flowing water courses.

A reasonably accurate estimate of the water temperature is necessary for a good description of the degradation of plant protection products in water which is used in the surface water model TOXSWA. Based on a consideration of basic physical processes that describe the influence of weather on the energy balance of natural water bodies, we propose to extend TOXSWA with a 1D bulk approach to estimate water temperature. Evaluation of such a system confirmed that it is physically realistic and yet simple, with limited data requirements. It is expected to perform reasonably well in most conditions, and fits well into the present structure of the TOXSWA model. In particular the estimation of degradation rates in shallow and turbid water will benefit from introducing the proposed system.

The TOXSWA model is used in the pesticide registration procedures in the Netherlands and the EU. This report documents the transient water flow module of TOXSWA, which simulates variable discharges and water depths in the edge-of-field ponds, ditches and streams of the EU FOCUS Surface Water Scenarios at an hourly resolution. It combines water conservation equations with water depth-discharge relations based upon weirs located downstream. In watercourses, backwater curves describe water depths as a function of distance to the weir. The water conservation equations consist of a base flow, excess water fluxes from drainage or runoff and an outflow. The conservation equations have been solved numerically using the finite difference method. A limited verification of the numerical solution has been undertaken. Example runs present model input and output, Het model TOXSWA wordt gebruikt in de toelatingsprocedures van bestrijdingsmiddelen in Nederland en in de EU. Dit rapport documenteert het onderdeel van TOXSWA met een niet-eenparige (dus in de stromingsrichting veranderende) waterstroming. Dit onderdeel simuleert op uurbasis veranderende afvoeren en waterdiepten in de FOCUS Oppervlaktewater Scenario’s van de EU: meertjes, sloten en beekjes grenzend aan landbouwpercelen. Waterconserveringsvergelijkingen worden gecombineerd met afvoerformules voor benedenstrooms gelegen stuwen, die het verband tussen de afvoer en de overstorthoogte geven. In de waterlopen beschrijven stuwkrommen het verloop van de waterdiepte met de afstand tot de stuw. De waterconserverings-vergelijkingen bevatten een basisafvoer, overtollige waterfluxen door drainagebuizen of via oppervlakte-afvoer en een uitstroming. De conserveringsvergelijkingen zijn numeriek opgelost met de eindige differentiemethode. De numerieke oplossing is beperkt geverifieerd. Voorbeeldsimulaties tonen de modelinvoer en -uitvoer. We bevelen aan om de wiskundige beschrijving van de waterstroming te verbeteren door een geleidelijk veranderende en discontinue waterstromingsbeschrijving te implementeren, dus met langs de waterloop in- of uitstromend water.Trefwoorden: FOCUS oppervlaktewater scenario’s, bestrijdingsmiddelen toelating, TOXSWA, niet-eenparige waterstroming.

Our interpretation is that the reduced runoff fluxes (water and mass) of the 20 ha upstream are combined with the unchanged runoff water fluxes of the remaining 80 ha upstream catchment. This implies that the reduction factor on exposure concentrations in FOCUS streams of Step 4 FOCUS scenarios calculations compared to those of Step 3 calculations approximately equals the reduction factor applied on the runoff fluxes (water and mass of the 20 ha upstream).

Spray drift, drainage and run-off are three major routes of pesticide entry into surface waters. Using spray-drift deposition tables and the MACRO, PRZM and TOXSWA models the exposure concentrations in surface waters can be assessed. Exposure scenarios have been developed as part of an EU evaluation process

The hydrological module of the model instrument Cascade describes kinetics of surface water flow in a 10 km2 catchment with a single outlet. Discharge measurements are available for calibration. The soil hydrological model SWAP is used to generate a description of drainage and infiltration. The SWQN model is used to simulate surface water flow in a detailed network representing the surface water channels and water management structures. The major terms of the surface water balance are drainage from the soil and the pump discharge at the outlet. Kinetics of cumulated discharge simulated at the outlet corresponds with cumulated discharge measured at the drainage pump. Model performance is also tested with a special simulation including a period of prolonged drought

This model calculates exposure concentrations in small watercourses or ponds; these concentrations are used in the pesticide registration procedure at EU level

The user-friendly shell SWASH, acronym for Surface WAter Scenarios Help, assists the user in calculating pesticide exposure concentrations in the EU FOCUS surface water scenarios. It is part of the exposure calculation procedure developed by the FOCUS Surface Water Scenarios Working Group, which has become part of the obligatory evaluation procedure to place an active substance on List 1 according to EU Directive 91/414/EEC. SWASH encompasses four separate tools and models: (i) FOCUS Drift Calculator, calculating pesticide entries through spray drift deposition, (ii) PRZM-3, calculating pesticide entries through run-off, (iii) MACRO, calculating pesticide entries through drainage and (iv) TOXSWA, calculating the behaviour of pesticides in small surface waters. It maintains a central pesticide properties database, prepares input for the PRZM, MACRO and TOXSWA models and then guides the user in performing the FOCUS Surface Water runs in a consistent and user-friendly way. Via the SWASH shell the user can enter the shells of the other models to perform the PRZM or MACRO model runs needed to assess the fate of the substance in the FOCUS water body systems using TOXSWA

In the Dutch registration procedure the TOXSWA model is used to calculate the exposure of aquatic organisms to the pesticides applied in agriculture. The transformation rates in water and sediment, needed as input for the computations, are not asked directly in the registration procedure. Various test guidelines for water-sediment studies are discussed; they only yield pesticide dissipation rates in water and sediment. Water-sediment studies for three compounds were simulated with TOXSWA to estimate the transformation rates from the measured data. It was found that a detailed interpretation of the experiments and reported data is crucial before the water-sediment studies can be simulated correctly. Using the model, pesticide transformation could be assigned to mainly one of the layers or to both layers. These transformation rates do not depend on system properties, such as volumes of water and sediment, nor on the surface area of their interface. The procedure has to be tested for more pesticides and studies. The factors determining microbial transformation of pesticides in aquatic systems were studied; this allows improved characterization of the systems by measurements.

The TOXSWA model calculates the acute exposure concentration and the average exposure concentrations (AECs) of pesticides in ditches after 4, 21 and 28 days. In a (global) sensitivity analysis based on the Monte Carlo method the most sensitive processparameters (pesticide properties) and the most sensitive system parameters (e.g. ditch dimensions) with respect to AECs were determined. The process parametes "transformation rate in the water layer", "coefficient for sorption to macrophytes" and "Henry coefficient" were identified as contributing most to the varation in the AECs. The full range of pesticides was characterized by these three parameters and subsequently the flow velocity, water depth and dry weight of macrophyutes were identified sas sensitive system parameters with respect to the AECs. Analytically, the water depth, bottom width of the ditch and the sorption coefficients for sorption to macrophytes and suspended solids were identified as sensitive parameters with respect to the acute exposure concentration.

The TOXSWA model describes the fate of pesticides entering field ditches by spray drift, atmospheric deposition, surface run-off, drainage or leaching. It considers four processes: transport, transformation, sorption and volatilization. Analytical andnumerical solutions corresponded well. A sample simulation showed that sorption to macrophytes can considerably reduce the concentration in the water phase. However, sorption to macrophytes leads to a slower transport and thus to longer residence times for the pesticide in the water layer. Sedimentation and resuspension of suspended solids were not considered, so that the model can only be applied for periods shorter than one month.

Onderzoek om een methodiek te ontwikkelen om bufferzones rondom beekdalen met natuurwetenschappelijke waarden aan te wijzen en te begrenzen. Deze nota is geschreven als aanvulling op het verschenen rapport naar aanleiding van het uitgevoerde onderzoek over de bufferzones (Adriaanse en Kemmers, 1988)