Aging Effects on the Availability of Herbicides to Runoff Transfer

Realistic estimation of sorption parameters is essential to predict long-term herbicide availability in soils and their contamination of surface water and groundwater. This study examined the temporal change of an effective partition coefficient Kdeff for the herbicides simazine, diuron, and oryzalin from a 0.12 ha field experiment during 7 vineyard growing seasons. Kdeff is the ratio of solvent extractable herbicide concentrations in the top soil (0-2 cm) to the average concentrations in runoff water and is considered to assess the effective availability of herbicides to runoff transfer. Kdeff increased largely with aging time since application, from values similar to those of the literature (determined in 24 h batch conditions, Kdref), up to 88, 164, and 30 times these initial values for simazine, diuron, and oryzalin respectively. The seasonal variation of Kdeff values between years and compounds could be adequately described by a unique model, taking into account the cumulative rainfall since application and Kdref of each compound. This simple model was able to represent the influence of the soil moisture content and its changes in the different biological and physicochemical processes that may contribute to the (bio)available, sorbed, or entrapped state of any of the studied herbicides with aging time under Mediterranean climate.(A)

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  • English

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  • Accession Number: 01060899
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD
  • Created Date: Sep 10 2007 1:27PM