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This article in JEQ

  1. Vol. 29 No. 4, p. 1298-1309
    Received: Aug 24, 1999

    * Corresponding author(s): jeh@dhi.dk
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Field Investigations and Modeling of Particle-Facilitated Pesticide Transport in Macroporous Soil

  1. Karen G. Villholth *,
  2. Nicholas J. Jarvis,
  3. Ole H. Jacobsen and
  4. Hubert de Jonge
  1. V KI, Agern Allé 11, DK-2970 Hørsholm, Denmark and Institute of Hydrodynamics and Water Resources, Technical Univ. of Denmark, DK-2800, Lyngby, Denmark.
    D ep. Soil Sciences, Swedish Univ. of Agricultural Sciences, Box 7072, 750 07 Uppsala, Sweden.



Physical and chemical non-equilibrium processes may facilitate the transport of pesticides and other chemicals through structured and macroporous soils. For sorbing pesticides, transport associated with a mobile colloidal or particulate phase represents an additional transport mechanismin structured soils that is not well understood. We investigated particle-facilitated transport of a sorbing pesticide (prochloraz, N-propyl-N-[2-(2,4,6-trichlorophenoxy)ethyl]imidazole-1-carboxamide) in a 5- by 5-m subsurface-drained field plot in a structured sandy loam in Denmark. Following pesticide application, three simulated rainfall events during an 8-d period were monitored in terms of drainage flow rate, content of particulate matter (>0.24 µm), and pesticide concentration in the solution and in the particulate phases in the drainage water. The fraction of pesticide loss to the drain was 0.2% of the applied mass, of which 6% was associated with the particulate phase. Macroporous flow paths appeared to be major routes of pesticide and particle transport. Preferential sorption to particles in the drainage water relative to bulk soil, and possibly also slow desorption from the particles, were assumed to influence the pesticide leaching in the particulate fraction. Based on experimental and reported data, the dual-porosity model MACRO, modified to account for particle mobilization and transport, could be calibrated to simulate the observations. Sensitive parameters for the particle and pesticide descriptions were identified.

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