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 Kow = 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.

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 Kow = 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 14 C 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.

Este trabajo se realizo dentro del marco de un proyecto multidisciplinario sobre la evaluacion de la utilizacion de zonas amorti-guadoras como uno de los mecanismos para combatir la contaminacion de aguas superficiales por plaguicidas. Estas zonas son eficaces para detener los plaguicidas transportados en las escorrentias, pero no existe mucha informacion sobre el futuro de las moleculas interceptadas. En el trabajo se evaluo la sorcion y la desorcion de dos herbicidas con propiedades muy diferentes: el isoproturon, moderadamente hidrofobo (log Kow = 2,5), la diflufenicanil, fuertemente hidrofobo (log Kow = 4,9), y la isopropila-nilina, un metabolito de la isoproturon, en suelos con diferentes tipos de ocupacion, barreras de hierba, zonas arboladas y par-celas de cultivo. Los experimentos se realizaron en laboratorio utilizando las moleculas marcadas con 14C. Los resultados mues-tran que la diflufenicanil y la isopropilanilina son mas retenidos que el isoproturon en los tres suelos. Los valores de Kd de las tres moleculas revelan que la sorcion del isoproturon y la diflufenicanil es mas fuerte en el horizonte superficial de la zona arbolada, donde el contenido de carbono es mas importante (ZB 0-2: Kd IPU = 15,1 L kg-1; Kd DFF = 169,2 L kg-1). En el caso del isopro-pilanilina, el Kd mas elevado es determinado en el horizonte superficial de la barrera de hierba (BE 0-2: Kd IPA = 53.1 L kg-1). Estos resultados estan relacionados con el diferente contenido y naturaleza de materia organica de acuerdo con el tipo de ocu-pacion del suelo.

The installation of vegetative buffer strips is one of the solutions proposed to combat pesticide pollution of surface water. These zones are effective in removing pesticides transported by runoff, but there is little information on what happens to the intercepted molecules. In this study, degradation of the herbicide isoproturon (IPU) [3-(4-isopropylphenyl)-1, 1-dimethylureal in soils from grassed strip, treed zones, and farm plots at the ARVALIS experimental site in La Jailliere, France was assessed. The degradation experiments were conducted in laboratory using isoproturon marked with C-14 in the benzene ring. Mineratization of IPU was especially important in the surface horizons of the soils from grassed strip and the treed zone. The formation of non-extractable, or low available residues was particularly important in the horizons where degradation is more active. Thus, the stabilization of isoproturon residues is highest in the topsoil horizons of the buffer strips. The rapid dissipation of IPU in the soils of the buffer zones indicates an interesting de-polluting function compared with agricultural soil since degradation and mineralization of IPU increase in the buffer zone soils. However, the weak degrading potential of the 30-60 cm horizons indicates that the effectiveness of these systems via degradation and stabilization processes of the products of interest is much more important in the topsoil horizons.

The in stal la tion of buffer zones is one of the so lu tions pro posed to com bat sur face wa ter con tam i na tion by pes ti cides. Ex isting stud ies show that these zones can limit the trans fer of agro chemi cals to wa ter bod ies. How ever, very lit tle in for ma tion ex ists about what hap pens to the in ter cepted prod ucts. Their evo lu tion is re lated to the physiochemical and bi o log i cal func tion ing of these buffer zones. This study ex am ined the re ten tion of a her bi cide, isoproturon, in soils from grassed buffer strips, for est area and crop ped soil from the ARVALIS ex per i men tal site in La Jailliere, France. The ex per i ments were car ried out un der con trolled lab o ra tory con di tions us ing isoproturon marked with 14 C in the ben zene ring. The re sults show that the re ten tion of the isoproturon was greater in the soils from the buffer zones than in the soils from the crop ped soil, par tic u larly in sur face ho ri zons, which have a higher con tent in or ganic mat ter. In ad di tion, the desorption of the mol e cule is more dif fi cult in the sur face ho ri zons of the buffer zones than in the worked layer of the crop ped soil. These find ings con firm the po ten tial value of buffer zones in pro tect ing sur face wa ter from ag ri cul tural con tam i nants.

La instalacion de zonas amortiguadoras es una de las soluciones propuestas para combatir la contaminacion de aguas superficiales por plaguicidas. Estas zonas son eficaces para detener los plaguicidas transportados en las escorrentias pero no hay mucha informacion sobre el devenir de las moleculas interceptadas. En este trabajo se evaluo la degradacion de un herbicida, el isoproturon (IPU) [3-(4-isopropilfenil)-1, 1-dimetilurea], en suelos provenientes de barreras de hierba, zonas arboladas y parcelas de cultivo del sitio experimental de ARVALIS en la Jailliere, Francia. Los experimentos de degradacion se realizaron en laboratorio utilizando el isoproturon marcado con 14C en el anillo bencenico. La mineralizacion del IPU fue especialmente importante en los horizontes superficiales de los suelos de las barreras de hierba y la zona arbolada. La formacion de residuos no extraibles es decir, poco disponibles, fue particularmente importante en los horizontes donde la degradacion es mas activa. Asi, la estabilizacion de los residuos de isoproturon es maxima en los horizontes superficiales de los dispositivos amortiguadores. La disipacion rapida del IPU en los suelos de las zonas amortiguadoras indica una funcion de descontaminacion interesante en comparacion con un suelo agricola, ya que la degradacion y la mineralizacion del IPU aumentan. Sin embargo, el debil potencial de degradacion de los horizontes 30-60 cm indica que la eficacia de estos sistemas via procesos de degradacion y estabilizacion de los productos interesados, es mucho mas importante en los horizontes superficiales de suelo.