Pollution of soils and ecosystems by a permanent toxic organochlorine pesticide: chlordecone—numerical simulation of allophane nanoclay microstructure and calculation of its transport properties

Woignier Thierry, Clostre Florence, Cattan Philippe, Lesueur Jannoyer Magalie. 2015. Pollution of soils and ecosystems by a permanent toxic organochlorine pesticide: chlordecone—numerical simulation of allophane nanoclay microstructure and calculation of its transport properties. AIMS Environmental Science, 2 (3) : 494-510.

https://doi.org/10.3934/environsci.2015.3.494

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Résumé : Pest control technology was introduced into the tropics without considering the specificity of their ecosystems and the risk of pollution was underestimated. Some volcanic soils (andosols) contain nanoclay (allophane) with a unique structure and porous properties compared to crystalline clays. Andosols are characterized by large pore volume and pore size distribution, a high specific surface area, and a fractal structure. These soils are more polluted than the other kinds of tropical soils but release less pollutants (chlordecone) to water and plants. The literature shows that the allophane microstructure favors accumulation and sequestration of chlordecone, an organochlorine pesticide, in andosols.<br />We used a numerical model to simulate the structure of allophane aggregates. The algorithm is based on a cluster-cluster aggregation model. From the simulated data, we derived the structural features, pore volume and tortuosity, and its transport properties, hydraulic conductivity and diffusion. We show that transport properties decrease because of the presence of allophane. We propose that low hydraulic conductivity and diffusion are important parameters to explain the high concentrations and trapping of pollutants in andosols.

Mots-clés Agrovoc : pollution du sol, pesticide, chlordécone, Andosol, toxicité des pesticides, pollution par l'agriculture

Mots-clés géographiques Agrovoc : Antilles françaises, France

Mots-clés libres : Chlordecone, Organochlorine pesticides, Soil contamination, Allophane clay, Andosols, Numerical simulation, Hydraulic conductivity, Diffusion

Classification Agris : H02 - Pesticides
P02 - Pollution
P33 - Chimie et physique du sol
P36 - Érosion, conservation et récupération des sols

Champ stratégique Cirad : Axe 1 (2014-2018) - Agriculture écologiquement intensive

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