Impact of vegetated filter strips on sorbed herbicide concentrations and sorption equilibrium in agricultural plots

Abstract

The objective was to investigate the impact of vegetated filter strips on exported atrazine and deethylatrazine concentrations [dissolved and sorbed to eroded sediments (>1.5 μm)], the deethylatrazine to atrazine ratio in water and sediments, the ratio of sorbed to dissolved herbicides in runoff and subsurface infiltration as well as field equilibrium state under natural climate during two seasons. We hypothesize that sorption equilibrium was not achieved in 2004 because of the short delay (<24 h) between herbicide application and the first rain event. In 2005, observations suggest that possible changing sorption equilibrium conditions were reached (20 days after atrazine application), especially for eroded sediments submitted to changing environmental conditions in subsurface. If confirmed by other experiments, this will raise the question of the representativeness of laboratory-determined soil sorption coefficients to predict the fate of pesticides.

Keywords:

• Buffer strip
• herbicide
• atrazine
• deethylatrazine
• sediment
• deethylatrazine to atrazine ratio
• sorption equilibrium

Acknowledgments

We thank Mr. Marc Duchemin. The authors thank field and laboratory technicians for their tremendous work. PL, main investigator, thanks the Natural Sciences and Engineering Research Council of Canada for financially supporting this study on the fate of herbicides in agro-ecosystems.