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Stabilisation des pesticides dans les sols sous forme de résidus on extractibles : Modélisation compartimentale pour l'évaluation de l'accumulation et de la libération différée de pesticides stabilisés.

Abstract : All pesticides form non- extractable (bound) residues in soils in variable percentage, according ti their chemical nature and the experimental conditions. In the context of repeated applications of pesticides, is it right to wait for modification of the formation kinetics of non-extractable residues? Accumulation of these residues would be until a plateau which the kinetics concentration level would be the resultant of the kinetics balance between the formation and the re-mobilization (degradation) of non extractable residues. To evaluate the formation of non-extractable residues and their possible re-mobilization, incubations have been realized with three soils, under laboratory conditions with 14C-atrazine and 14C-isoproturon, with 14C-atrazine applied on lysimètres in natural conditions. The residues evaluation provided information on quality and quantity of residues formed and their kinetics evolution of bound residues. The most significant effect of repeated applications of pesticides is the induction of biological activity of soils specialized in their degradation. The result is a quick degradation of the pesticide, going until the mineralization, with an important decreasing of it persistence and a number of intermediates remaining in the soil. This rapid degradation enters into competition with some phenomenon often slow, responsible for the formation of non-extractable residues. The compartment approach to modeling behavior in the soils allows estimating the re-mobilization flow constant kij, and classifying the most significant flow between the three compartments identified, according to the residues extraction and the solvent used. Bound residues were mostly formed from extractible residues with methanol. But a formation of bound residues from water-soluble residues, the most disponible in the soil, is also put out. This point is probably in relation with the intervention of the bacterial biomass of the soil which is itself a storage compartment of bound residues. But this bacterial biomass is also a transit compartment and a chemical activation compartment through the metabolites formation, intermediates often most reactive than the active substance (e.g. isoproturon). The bound residues mobilization constant kij such estimated, are higher for atrazine than for isoproturon. These kij are systematically slower in the acid soil than in the basic soil. In the basic soil, the induction of a specific biological activity able to degrade quickly the herbicide atrazine and isoproturon increase the re-mobilization's constants of their bound residues, which shows the ability of the micro-organisms such actived to degrade the residues disponible with low availability. These mobilization flow constants can be used to calculate the half life (DT50). The DT50 of non-extractable residues are relatively low in soils having a specific biological activity for the pesticide degradation. In other soils and above all for isoproturon, the DT50 of non-extractable residues are highest, exceeding sometimes on year. The values of mobilization flow constants can be used to realize risk estimations of re-mobilization. Nevertheless, the use of results is being confronted with the difficulty to generalize the data for one pesticide for application to others, and/or in others soils.
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https://pastel.archives-ouvertes.fr/pastel-00825687
Contributor : Macaire Rodrigue Edzang-Ondo Connect in order to contact the contributor
Submitted on : Friday, May 24, 2013 - 12:37:46 PM
Last modification on : Friday, August 5, 2022 - 2:38:10 PM

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  • HAL Id : pastel-00825687, version 1

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Macaire Rodrigue Edzang-Ondo. Stabilisation des pesticides dans les sols sous forme de résidus on extractibles : Modélisation compartimentale pour l'évaluation de l'accumulation et de la libération différée de pesticides stabilisés.. Sciences de l'environnement. AgroParisTech, 2005. Français. ⟨pastel-00825687⟩

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