The performance of buffer zones for removing pesticides from runoff water varies greatly according to landscape settings, hydraulic regime, and system design. Evaluating the performance of buffers for a range of pesticides and environmental conditions can be very expensive. Recent studies suggested that the fluorescent dyes uranine and sulforhodamine B could be used as cost-effective surrogates of herbicides to evaluate buffer performance. However, while transformation mechanisms in buffers have been extensively documented, sorption processes of both dyes have rarely been investigated. In this study, we measured the adsorption, desorption, and kinetic sorption coefficients of uranine and sulforhodamine B for a diverse range of buffer zone materials (soils, litters, plants) and compared the adsorption coefficients (Kd) to those of selected herbicides. We also compared the global sorption capacity of 6 ditches, characterized by varying proportions of the aforementioned materials, between both dyes and a set of four herbicides using the sorption-induced pesticide retention indicator (SPRI). We found that both the individual Kd of uranine for the diverse buffer materials and the global sorption capacity of the ditches are equivalent to those of the herbicides diuron, isoproturon, and metolachlor. The Kd of sulforhodamine B on plants and soils are equivalent to those of glyphosate, and the global sorption capacities of the ditches are equivalent for both molecules. Hence, we demonstrate for the first time that uranine can be used as a proxy of moderately hydrophobic herbicides to evaluate the performance of buffer systems, whereas sulforhodamine B can serve as a proxy for more strongly sorbing herbicides.

La reduction des emissions d'ammoniac pour atteindre des objectifs environnementaux tels que stopper la diminution de la superficie des ecosystemes non proteges contre l'acidification et l'eutrophisation va occuper une place de plus en plus importante dans la strategie de lutte contre la pollution. En raison de la reduction des emissions d'oxydes de soufre et d'azote operee au cours des 20 dernieres annees dans le cadre de la Convention sur la pollution atmospherique transfrontiere a longue distance, il est fort probable qu'en 2010 c'est l'ammoniac qui contribuera le plus aux emissions gazeuses responsables de l'eutrophisation et de l'acidification. D'ou l'importance de prendre des maintenant des mesures efficaces contre ce polluant, et ce a l'echelle continentale