Mapping Ground Water Vulnerability to Pesticide Leaching

To monitor the progress of the EU Thematic Strategy on the Sustainable Use of Pesticides, the Netherlands Environmental Assessment Agency (MNP) has developed a simple pesticide leaching indicator. This indicator was developed using results from a pan-European, process-based, numerical pesticide leaching model (EuroPEARL).

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• The pan-European pesticide leaching model

Abstract

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 pa-rameter 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 years. The metamodel explains over 90% of the variation of the original model with only four in-dependent 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 pre-dicted 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.