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

International audienc

Natural nano materials trapp pollutants in soils

Persistent pesticides led to long term pollution of soils and consequently contaminate rivers, groundwater, ecosystems and finally human beings. Volcanic soils (andosols) are generally more polluted than the other kinds of tropical soils but data show that andosols release less pesticides to percolating water and crops. Andosols contain amorphous clays (allophane) which present unique structures and physical properties compared to crystalline clays. Allophane aggregates have physical features very close to that of nano porous materials like synthetic gels: large pore volume and water content, a broad pore size distribution, a high specific surface area and a fractal structure. The aim of the study was to show the influence of the features (nano materials structure, shrinkage during drying) of these natural gels on the pesticide retention. Our study confirms that the soil to crop pesticide transfer is lower in andosols compared to other volcanic soils. Associated to high organic matter content, the allophane microstructure favor pollutants (chlordecone) accumulation in soils. We put forth the importance of the nano porous features of allophane (the associated tortuous microstructure) but also the pore collapse during drying, for pollutant trapping in soils

Des parcelles aux cours d'eau : transferts de chlordécone dans les eaux

International audienceThe 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

Soil interfaces in a changing world

The context of this study is the pollution of soils and water by a persistent organo-chlorinated insecticide, chlordecone, in a tropical environment. The application of chlordecone to control the banana black weevil has led to continuing diffuse pollution of soils, and to its being a source of contamination for cultivated plants, as well as for terrestrial and marine ecosystems. Chlordecone is toxic and stable and is considered to be a persistent organic pesticide. Consequently, the amounts of chlordecone that could migrate through the environment and contaminate agricultural products need to be controlled. We measured the impact of two composts (5% weight) on chlordecone sequestration in andosols. To this end, we first characterized the transfer of chlordecone from soil to water, and then its transfer from soil to plants. After 3 months of maturation, soil-water and soil-plant transfers were reduced by a factor of from 3 to 10. We also showed that adding compost to contaminated soils increases chlordecone sequestration because it leads to changes in soil microstructure in the form of pore collapse and closure of the fractal structure of the allophane content

A participatory method to design innovative sustainable cropping systems for citrus production at the field scale in the french West Indies

International audienc

Crop protection and environmental health : legacy management and new concepts

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

Field validation of chlordecone soil sequestration by organic matter addition

Purpose The use of chlordecone (CLD) has caused pollution of soils, which are now a source of contamination for crops and ecosystems. Because of its long-term impacts on human health, exposure to CLD is a public health concern and contamination of crops by CLD must be limited. To this end, we conducted field trials on chlordecone sequestration in soil with added compost. Materials and methods The impact of added compost on chlordecone sequestration was measured in nitisols. After characterization of the soil, the transfer of chlordecone from soil to water was assessed in a leaching experiment and from soil to two crop plants in a nitisol plot. Finally, to understand the underlying processes, changes in CLD content were measured in soil fractions and soil porous properties were assessed after the addition of compost. Results and discussion A rapid seven-fold decrease in water extractable CLD was observed in amended soils. Five percent amendment led to a significant reduction in the contamination of crops by CLD; edible radish tubers were 50% more contaminated without added compost and cucumber fruits were 60% more contaminated. After the addition of compost, CLD content increased in the fraction of pre-humified or partially mineralized organic debris. Finally, in contrast to andosols, adding compost to nitisols did not affect the soil microstructure. Conclusions Increasing chlordecone sequestration by adding compost could be an alternative solution until soil decontamination techniques become available. This could be a provisional way to control further release of CLD from contaminated soils towards other environmental compartments

Determination of soil content in chlordecone (organochlorine pesticide) using near infrared reflectance spectroscopy (NIRS)

Chlordecone is a toxic organochlorine insecticide that was used in banana plantations until 1993 in the French West Indies. This study aimed at assessing the potential of near infrared reflectance spectroscopy (NIRS) for determining chlordecone content in Andosols, Nitisols and Ferralsols from Martinique. Using partial least square regression, chlordecone content conventionally determined through gas chromatography-mass spectrometry could be correctly predicted by NIRS (Q(2) = 0.75, R-2 = 0.82 for the total set), especially for samples with chlordecone content 12 mg kg(-1), nevertheless ca. 80% samples were correctly predicted when the set was divided into three or four classes of chlordecone content. Thus NIRS could be considered a time- and cost-effective method for characterising soil contamination by chlordecone

De la production fruitière intégrée à la gestion écologique des vergers aux Antilles

National audienceLa forte anthropisation aux Antilles françaises, la pression des monocultures de banane et de canne à sucre, et l’usage immodéré de pesticides, ont abouti à la pollution persistante d’une partie importante des sols de la SAU ainsi que des eaux de rivière et des nappes phréatiques. Si, dans les dix dernières années, la recherche de moyens de lutte biologique contre les insectes a été prioritaire, la lutte contre les adventices continue d’être un problème central pour les arboriculteurs qui ne peuvent pas financièrement substituer complètement les fauchages mécaniques à l’utilisation fréquente d’herbicides. Le Cirad porte maintenant ses efforts sur l’introduction de plantes de couverture, graminées et légumineuses, dans des systèmes de culture innovants où les arbres fruitiers, le couvert herbacé et les animaux peuvent être associés de manière judicieuse pour une gestion écologique de la parcelle. Chacune des trois composantes est choisie pour apporter une meilleure durabilité au système

Soil microstructure and organic matter : keys for chlordecone sequestration

Past applications of chlordecone, a persistent organochlorine pesticide, have resulted in diffuse pollutionof agricultural soils, and these have become sources of contamination of cultivated crops as well as ter-restrial and marine ecosystems. Chlordecone is a very stable and recalcitrant molecule, mainly presentin the solid phase, and has a strong affinity for organic matter. To prevent consumer and ecosystemexposure, factors that influence chlordecone migration in the environment need to be evaluated. In thisstudy, we measured the impact of incorporating compost on chlordecone sequestration in andosols asa possible way to reduce plant contamination. We first characterized the transfer of chlordecone fromsoil to plants (radish, cucumber, and lettuce). Two months after incorporation of the compost, soil-planttransfers were reduced by a factor of 1.9-15 depending on the crop. Our results showed that addingcompost modified the fractal microstructure of allophane clays thus favoring chlordecone retention inandosols. The complex structure of allophane and the associated low accessibility are important charac-teristics governing the fate of chlordecone. These results support our proposal for an alternative strategythat is quite the opposite of total soil decontamination: chlordecone sequestration. (Résumé d'auteur