title: Effect of pesticide fate parameters and their uncertainty on the selection of 'worst-case' scenarios of pesticide leaching to groundwater.
abstract: BACKGROUND
  For the registration of pesticides in the European Union, model simulations for worst-case scenarios are used to demonstrate that leaching concentrations to groundwater do not exceed a critical threshold. A worst-case scenario is a combination of soil and climate properties for which predicted leaching concentrations are higher than a certain percentile of the spatial concentration distribution within a region. The derivation of scenarios is complicated by uncertainty about soil and pesticide fate parameters. As the ranking of climate and soil property combinations according to predicted leaching concentrations is different for different pesticides, the worst-case scenario for one pesticide may misrepresent the worst case for another pesticide, which leads to 'scenario uncertainty'.
  
  
  RESULTS
  Pesticide fate parameter uncertainty led to higher concentrations in the higher percentiles of spatial concentration distributions, especially for distributions in smaller and more homogeneous regions. The effect of pesticide fate parameter uncertainty on the spatial concentration distribution was small when compared with the uncertainty of local concentration predictions and with the scenario uncertainty.
  
  
  CONCLUSIONS
  Uncertainty in pesticide fate parameters and scenario uncertainty can be accounted for using higher percentiles of spatial concentration distributions and considering a range of pesticides for the scenario selection.
authors.affiliation: Agrosphere, ICG-4, Forschungszentrum Jülich GmbH, Jülich, Germany. j.vanderborght@fz-juelich.de
authors.forename: Jan
authors.initials: J
authors.lastname: Vanderborght
authors.forename: Aaldrik
authors.initials: A
authors.lastname: Tiktak
authors.forename: Jos J T I
authors.initials: JJ
authors.lastname: Boesten
authors.forename: Harry
authors.initials: H
authors.lastname: Vereecken
mesh_terms: D002980:Climate; D003198:Computer Simulation; D004784:Environmental Monitoring; D005062:European Union; D010575:Pesticides / Q000032:analysis* / Q000737:chemistry; D018570:Risk Assessment; D012989:Soil Pollutants / Q000032:analysis* / Q000737:chemistry; D035501:Uncertainty; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry
chemical_list: D010575:Pesticides; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical