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Effects of clay microstructure and compost quality on chlordecone retention in volcanic tropical soils: consequences on pesticide lability and plant contamination

Fernandes P., Jannoyer-Lesueur M., Soler A., Achard R., Woignier T.. 2010. In : Eds. Robert J. Gilkes and Nattaporn Prakongkep. Soil Solutions for a Changing World: 19th World Congress of Soil Science, Brisbane, Australia, 1-6 August 2010. Brisbane : International Union of Soil Sciences, 4 p.. World Congress of Soil Science. 19, 2010-08-01/2010-08-06, Brisbane (Australie).

The scientific and economic context of our study is related to the pollution of the soils, fresh and marine water by a persistent organochlorine pesticide (chlordecone) in a tropical context (French West Indies). The former application of chlordecone results today in a diffuse pollution in agricultural soils, which are sources of contamination for cultivated roots, tubers, vegetables and terrestrial and marine ecosystems. Chlordecone is a very though and stable molecule (considered as a POP), it is mainly present in solid phase and has a strong affinity with organic matters. To prevent consumers and ecosystems exposure, it is thus necessary for us to evaluate the factors that influence chlordecone migration in the environment. In our research, we studied the impacts of clay microstructure on the chlordecone retention, comparing allophanes (amorphous clays present in andosols) and halloysite clays (type 1/1). We showed that allophane aggregates had a greater ability to trap chlordecone mainly due to their fractal structure. We also measured the effects of added composts on soil microstructure and on chlordecone lability and transfer rate from soil to plant 3 and 6 months after incorporation. The intensity and persistence of these effects were related to the initial quality and richness of the added composts.

Mots-clés : chlordécone; andosol; sol volcanique; structure du sol; argile; pesticide; pollution par l'agriculture; pollution du sol

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