The Danish EPA have increasingly used models in the assessment of pesticides mobility. They have set up certain requirements for a model study under Danish conditions. These requirements are printed on a CD-rom, which Danish EPA released last year. The CD includes the input files for the model MACRO, such as climate data and the parameter file for two scenarios. It furthermore includes a thoroughly description of the scenarios (soil types, water balances, climate data etc.). The scenarios represent a typical Danish sandy soil and a loamy clay soil. A study concludes that models which not include a description of preferential flow are not feasible for prediction of leaching in macroporous soils. Therefore, the Danish EPA have decided to use the Swedish model MACRO. Since the model is not validated, a realistic worst case must be covered with respect to pesticide parameters, application rate, crop, etc. A study has shown that hourly precipitation data can give up to 12 times higher leaching, than using daily precipitation data.
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