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Rôle régulateur de la macrofaune lombricienne dans la dynamique de l'herbicide atrazine en sol cultivé tempéré

Abstract : This research task falls under the context of contamination of the grounds by the pesticides used in agriculture. These problems are a major and current stake since the space-time extent of the contamination is ignored. It is thus a question here of better including/understanding the dynamics of the weedkillers in the ecosystems for better evaluating the risks of them a priori and more precisely of knowing up to what point and by which mechanisms the edaphic organizations control their dynamic physics and chemical. Two alternative assumptions were tested with the model molecule weedkiller, the atrazine: i) the macrofaune lombrician contributes to degradation partial or total of the atrazine by stimulating the activity of the degrading microflore and ii) the macrofaune lombrician supports the connection of the atrazine with the argilo-humic complexes of the ground, within microsites supporting the retention and the remanence of the weedkiller. Experiments in presence and absence of Lumbricus terrestris and Aporrectodea caliginosa were carried out on various space and temporal scales, with atrazine-14C. Acting of the role of the macrofaune lombrician, the experimental results obtained showed that: ? l'ingestion of the ground by the macrofaune lombrician supports the adsorption of l'atrazine and led to a redistribution of the quantities of atrazine and its residues dependent in biostructures (with in the order: walls of galleries - dejections excreted in the galleries - dejections on the surface or turricules - intestinal contents or endentères) compared to the ground not introduced and had with an enrichment out of organic carbon combined with a stronger microporosity? conversely, the mineralisation of l'atrazine is not stimulated not even slowed down in the presence of worms. It is the passage of the ground in the digestive tract, during which the structuring of the initial bacterial communities of the ground is modified, which limits the total degradation of the atrazine by microbial way? a significant reduction in the genetic potential degrading (genes atz) consecutive with ingestion was highlighted, suggesting a strong déplétion of the degrading bacterial population Pseudomonas sp. ADP. From these original results, it is concluded that the activity of the macrofaune lombrician in the grounds would tend to increase the time of residence of the pollutant and thus its remanence but would be opposed to its elimination by natural biological breakdown by the bacteria.
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Submitted on : Friday, November 19, 2004 - 4:54:47 PM
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  • HAL Id : tel-00007435, version 1

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Anne Kersante. Rôle régulateur de la macrofaune lombricienne dans la dynamique de l'herbicide atrazine en sol cultivé tempéré. Ecologie, Environnement. Université Rennes 1, 2003. Français. ⟨tel-00007435⟩

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