1 Department of Agroecology - Soil Physics and Hydropedology, Department of Agroecology, Science and Technology, Aarhus University2 Danish EPA, Copenhagen K3 Geological Survey of Denmark and Greenland, Copenhagen K4 Department of Environmental Engineering5 Department of Agroecology - Soil Physics and Hydropedology, Department of Agroecology, Science and Technology, Aarhus University
The environmental risk assessment of pesticides in Europe is based on crop relevant exposure scenarios for the intended uses. A tiered FOCUSsw modelling approach (Step 1-4) is used to provide harmonised exposure data for the aquatic risk assessment. At FOCUSsw Step 3 exposure is modelled in different water bodies (pond, ditch and stream) in 10 scenarios representing geo-climate conditions across Europe. The model provides estimates of surface water concentration, based on the intended use, taking into account potential input routes (drift, drainage and run-off). Leaching and subsequent transport through the drainage system poses an important contamination pathway allowing rapid transport of pesticides to the surface water system. With FOCUSsw this input is modelled via the 1 dimensional root zone model MACRO allowing preferential transport to occur in the unsaturated zone. Although models (such as MACRO) are widely used within the registration process, their validation requires further work, not least because of the limited availability of field data. The Danish Pesticide Leaching Assessment Programme (PLAP), an intensive monitoring programme which is used to evaluate the risk of leaching of pesticides under field conditions, aims to analyse whether pesticides applied in accordance with granted uses enter the aquatic environment in unacceptable concentrations. Within this programme a high resolution data set comprising 10 years of various pesticide concentrations in drainage from 3 field sites (1.7 – 2.3 ha, sandy loam) are available for model validation. Moreover, a “site specific” setup of the MACRO model already calibrated and validated with respect to water and non reactive solute transport is available from these field sites. For a sub-set of pesticides representing a range of use patterns and inherent properties (e.g. sorption potential, persistency and toxicity) output from drain to surface water has been assessed from both measured and modelled data. The latter comprising output from the MACRO model parameterised either via the FOCUSsw setup (relevant scenarios) or the “site specific setup” applied at the PLAP sites. Output from monitoring and the two modelling approached are compared and uncertainties of the different approached are discussed. It is considered how monitoring data from post registration systems can be “optimised” in order to improve their usability in risk assessment (e.g. validation of modelling, output format).