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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 90 th 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.

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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. The new 3D organic matter map has been generated in two steps; first a trend model was developed based on data at 1210 locations selected using a well-defined stratified random sampling scheme followed by interpolation of the residuals using about 770 000 determinations of organic matter content from the Dutch Soil Information System (BIS-Nederland). In general, the predicted soil organic matter contents in the top layer of arable soils correspond well with those measured. Because preliminary calculations showed higher leaching concentrations using the new GeoPEARL version, the consequences of this new version in combination with the Dutch Decision Tree for leaching to groundwater was investigated. The results of the computations revealed that the PEC90 calculated using GeoPEARL in tier 2 is higher than the PEC80 calculated using FOCUSPEARL in many cases. This inconsistency between the first and second tiers could be remedied by the introduction of a calibration factor.Calibration factors of 5 and 10 are necessary to ensure consistency between these tiers for spring and autumn applications, respectively. Suggestions are given for improvement and justification of the calibration factors in the Decision Tree. It is recommended to systematically compare the predicted leaching concentration in groundwater abstraction areas with that in the Dutch agricultural area as a whole. To improve the reliability of model predictions for these smaller areas, development a more flexible schematisation is needed.Keywords: decision tree, GeoPEARL, groundwater, leaching, national authorisation, plant protection product, pesticide, soil organic matter • Acquisition, duplication and transmission of this publication is permitted with clear acknowledgement of the source.• Acquisition, duplication and transmission is not permitted for commercial purposes and/or monetary gain.• Acquisition, duplication and transmission is not permitted of any parts of this publication for which the copyrights clearly rest with other parties and/or are reserved. Analysis of the data showed that the organic matter content in the top 0.3 m of arable soil profiles in GeoPEARL was 1.5. to 2 times higher than that measured in these soils. This difference was introduced in the schematisation at the time of the development of the schematisation, because the aim was to estimate the average organic matter content in a grid cell, which results from a mixture of grassland and arable soil profiles. The consequence of the error in the organic matter content of arable soils is that the leaching concentrations to groundwater are underestimated. To remedy this, the Working Group on the Dutch Decision Tree for Leaching to Groundwater started to work on the improvement of the soil schematisation for G...

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materials. Wageningen, Wageningen Environmental Research, Report 2841. 48 pp.; 10 fig.; 12 tab.; 7 ref.Sorption of pesticides to solid materials used in soilless stonewool cultures is relevant because it may reduce emissions to surface water. The sorption of pymetrozine and dimethomorph was studied in batch experiments with clean stonewool, drip-irrigation pipes, transport pipes and the plastic foil surrounding the stonewool. The sorption coefficient of stonewool was found to be 0.2 L/kg for pymetrozine and 1.0 L/kg for the two isomers of dimethomorph. Sorption of pymetrozine to the pipes and the foil was negligibly small. The sorption coefficients of the two isomers of dimethomorph were 0.07-0.12 L/kg for the transport pipes, 0.14-0.16 L/kg for the drip-irrigation pipes and 1.2-1.5 L/kg for the foil. Studies were performed in which an aqueous solution of the pesticides was circulated through stonewool mats containing an intact sweet-pepper plant (triplicate plant systems) sampled at the end of the growing cycle. Pymetrozine did not show any interaction with the solid phases in these circulation studies. Dimethomorph showed a concentration decrease that was 10% higher than expected from the batch studies with clean stonewool. An exploratory calculation showed that this 10% may be the result of partitioning into the roots and that this may correspond to 30% decrease in a stonewool growing system in the greenhouse. It is recommended to incorporate (i) sorption to stonewool and drip-irrigation pipes and (ii) partitioning into the roots into the GEM model and to assess the sensitivity of the emission concentrations to these processes for substances like dimethomorph.Keywords: plant protection products, pesticides, soilless culture, stonewool • Acquisition, duplication and transmission of this publication is permitted with clear acknowledgement of the source.• Acquisition, duplication and transmission is not permitted for commercial purposes and/or monetary gain.• Acquisition, duplication and transmission is not permitted of any parts of this publication for which the copyrights clearly rest with other parties and/or are reserved.Wageningen Environmental Research assumes no liability for any losses resulting from the use of the research results or recommendations in this report. Wageningen Environmental Research Report 2841 | ISSN 1566-7197Photo cover: Arrienne Matser (stonewool batch sorption system) Contents We thank furthermore Ton van der Linden (RIVM) and our colleague Louise Wipfler for useful comments that helped to improve this report. | Wageningen Environmental Research report 2841Wageningen Environmental Research report 2841 | 7 SummaryIt is a point of discussion whether sorption of plant protection products to substrate materials should be included in the GEM model which is currently used to assess the emission of PPPs to surface water from soilless cultures in Dutch greenhouses. Only very little data on this sorption are available in literature. Therefore the sorption of two pesticides (pymetrozine and...

UK The GEM model developed for soilless cultures consists of different submodels (A) for applications to crops grown on mats by drip irrigation, (B) for spray applications to crops grown on such mats, and (C) is for spray applications to crops grown in pots in an ebb/flood system (GEM-A, GEM-B, and GEM-C). The descriptions of the processes for pesticide behaviour in these submodels were reviewed, considering also their consistency with measurements available in the literature. For GEM-A it is recommended to include sorption to the mats, the foil surrounding the mats and the irrigation pipes and to include partitioning between the water in the mats and the plant roots. For GEM-B it is recommended to include direct contamination of the substrate mats and the troughs resulting from spray and Low Volume Mister (LVM) applications. For GEM-B and GEM-C it is recommended (i) to revise the procedures for calculating the initial concentrations in the air and the condensation water, (ii) to include deposition onto the roof by spray and LVM applications, (iii) to revise the procedure for calculating the volatilisation rates from the plant surfaces. For GEM-C it is recommended (i) to omit the sorption equilibration between the bottom 10 cm of the soil in the pots and the water on the ebb/flood tables, (ii) to revise the procedure for the flux in the gas phase between the greenhouse air and the top layer of the soil in the pots, and (iii) to use a crop-specific value for the fraction of the surface area covered by the pots.