title: Field leaching of pesticides at five test sites in Hawaii: modeling flow and transport.
abstract: BACKGROUND
  Physically based tier-II models may serve as possible alternatives to expensive field and laboratory leaching experiments required for pesticide approval and registration. The objective of this study was to predict pesticide fate and transport at five different sites in Hawaii using data from an earlier field leaching experiment and a one-dimensional tier-II model. As the predicted concentration profiles of pesticides did not provide close agreement with data, inverse modeling was used to obtain adequate reactive transport parameters. The estimated transport parameters of pesticides were also utilized in a tier-I model, which is currently used by the state authorities to evaluate the relative leaching potential.
  
  
  RESULTS
  Water flow in soil profiles was simulated by the tier-II model with acceptable accuracy at all experimental sites. The observed concentration profiles and center of mass depths predicted by the tier-II simulations based on optimized transport parameters provided better agreements than did the non-optimized parameters. With optimized parameters, the tier-I model also delivered results consistent with observed pesticide center of mass depths.
  
  
  CONCLUSIONS
  Tier-II numerical modeling helped to identify relevant transport processes in field leaching of pesticides. The process-based modeling of water flow and pesticide transport, coupled with the inverse procedure, can contribute significantly to the evaluation of chemical leaching in Hawaii soils.
authors.affiliation: Faculty of Civil Engineering, Czech Technical University in Prague, Prague, Czech Republic. dusek@mat.fsv.cvut.cz
authors.forename: Jaromir
authors.initials: J
authors.lastname: Dusek
authors.forename: Michal
authors.initials: M
authors.lastname: Dohnal
authors.forename: Tomas
authors.initials: T
authors.lastname: Vogel
authors.forename: Chittaranjan
authors.initials: C
authors.lastname: Ray
mesh_terms: D003198:Computer Simulation; D004784:Environmental Monitoring / Q000379:methods*; D006254:Hawaii; D008956:Models, Chemical; D010575:Pesticides / Q000032:analysis / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
chemical_list: D010575:Pesticides; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical