Sorption properties of isoproturon and diflufenican on ditch bed sediments and organic matter rich materials from ditches, grassed strip and forest soils.
Etude de l'adsorption de l'isoproturon et du diflufénicanil sur des sédiments et des substrats riches en matière organique issus de fossés, de bandes enherbées et de sols forestiers.
Résumé
In order to limit non-point source pollution from agricultural pesticides, research programs have been developed to study the different transport and dissipation mechanisms of pesticides from fields to rivers. Sorption is considered as one of the major processes responsible for the decrease of pesticide concentration in run-off. Sorption is thought to be especially important in buffer zones installed to reduce pesticides losses by runoff from agricultural areas. This can occur in grassed areas, such as grassed buffer strips, or forested land, and also in linear ditches collecting surface and drainage waters. Buffer zones contain many elements which could influence pesticide sorption. For example, in ditches a great variety of solid materials may act as sorbents: grasses, tree leaves, woody materials in different states of decomposition, organo-mineral particles or sediments originating from soil erosion. Laboratory experiments were carried out to investigate some of the intrinsic properties of different types of sediment/organic litter. Adsorption and desorption kinetics were studied with the herbicides isoproturon, and diflufenican. Batch experiments were used to determine sorption isotherms and Kd values. The comparison of the different results shows that beside the sorbent organic matter content, which was the main contributory factor for herbicide sorption, organic matter decomposition and origin had to be taken into account to explain the differences observed between ditch, grassed soil and forest litter materials.