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[Departement_IRSTEA]Territoires [TR1_IRSTEA]DTAM; International audience; The book deals with a long term pollution problem, generated by the former use of organochlorine pesticides. Through a case study of the chlordecone pollution in the French West Indies, the authors illustrate a global and systemic mobilization of research institutions and public services. This "management model", together with its major results, the approach and lessons to be learned, could be useful to other situations. This book gathers all the works that have been carried out over the last ten years or more and links them to decision makers’ actions and stakeholders’ expectations. This reference fills a gap in the literature on chronic pollution.

Chlordecone, an organochlorine insecticide, pollutes soils and contaminates crops and water resources and is biomagnified by food chains. As chlordecone is partly trapped in the soil, one possible alternative to decontamination may be to increase its containment in the soil, thereby reducing its diffusion into the environment. Containing the pesticide in the soil could be achieved by adding compost because the pollutant has an affinity for organic matter. We hypothesized that adding compost would also change soil porosity, as well as transport and containment of the pesticide. We measured the pore features and studied the nanoscale structure to assess the effect of adding compost on soil microstructure. We simulated changes in the transport properties (hydraulic conductivity and diffusion) associated with changes in porosity. During compost incubation, the clay microstructure collapsed due to capillary stresses. Simulated data showed that the hydraulic conductivity and diffusion coefficient were reduced by 95 and 70 % in the clay microstructure, respectively. Reduced transport properties affected pesticide mobility and thus helped reduce its transfer from the soil to water and to the crop. We propose that the containment effect is due not only to the high affinity of chlordecone for soil organic matter but also to a trapping mechanism in the soil porosity.

Crisis Management of Chronic Pollution: Contaminated Soil and Human Health deals with a long term pollution problem, generated by the former use of organochlorine pesticides. Through a case study of the chlordecone pollution in the French West Indies, the authors illustrate a global and systemic mobilization of research institutions and public services. This "management model", together with its major results, the approach and lessons to be learned, could be useful to other situations. This book gathers all the works that have been carried out over the last ten years or more and links them to decision makers' actions and stakeholders' expectations. This reference fills a gap in the literature on chronic pollution.

International audience

Diagnosis and Management of Field Pollution in the Case of an Organochlorine Pesticide, the Chlordecone

Allophanic soils are interesting in terms of environmental properties especially because of their potentialities as sinks for "greenhouse gases" by the way of C sequestration. These volcanic soils contain amorphous clays (allophanes) and exhibit higher organic carbon content than the one measured in other clay soils. We measured the C content of a set of allophanic soils and showed that the C content is positively correlated to the allophane content. We also measured the part of organic matter transformed into CO2 during a respiration experiment and showed that the decomposition is lowered as the soils allophane content increases. Allophane aggregates are very close to the synthetic gels: high specific surface area large pore volume, fractal structure, large water content and important irreversible shrinkage during drying. In this work we characterized by Small Angle X-Ray Scattering (SAXS) the fractal structure of the allophane aggregates at the nano scale. We hypothesized that the peculiar structure and the associated low accessibility of the allophanic soils could explain the high organic carbon content and the associated poor transformation into CO2. The tortuous structure of the allophane aggregates plays the role of a labyrinth which fix and traps soil organic carbon.