Pesticide sorption and desorption from soils having different land use

This study was carried out within the framework of a multidisciplinary project for evaluating buffer zones for combating pesticide contamination of surface water. Such areas are effective in removing pesticides transported by run-off; however, little information is available about the fate of the pesticides so intercepted. Two herbicides having contrasting properties (isoproturon, moderately hydrophobic (log Kow = 2.5), diflufenican, strongly hydrophobic (log K ow = 4.9)) and isopropylaniline (an isoproturon metabolite) were used for characterising sorption and desorption from soil having three different land uses: grass buffer strip, woodland and cultivated plot. The experiments were carried out in controlled laboratory conditions using isoproturon labelled with 14C in the benzene ring. The results demonstrated that diflufenican and isopropilaniline retention was more significant than isoproturon in three soils. The three molecules’ Kd values revealed that isoproturon and diflufenicanil retention was more important in woodland soil where carbon content was more significant (ZB 0-2: Kd IPU = 15.1 Ls kg-1; Kd DFF = 169.2 Ls kg-1). Isopropilanilina Kd was higher in grass buffer strip soil (BE 0-2: Kd IPA = 53.1 L kg-1). These differences were related to different organic matter content and nature according to the type of land use