Modeling the temporal dynamics of chlordecone in the profile of tropical polluted soils as affected by land use change

The insecticide chlordecone (CLD) was applied from 1972 to 1993 to banana fields in the French Antilles, which resulted in the long-term pollution of soils and the contamination of crops and water resources. We coupled two biophysical models describing CLD and soil organic carbon (SOC) dynamics to determine the impact of a change of cropping system from banana to vegetable crops on the temporal pattern of CLD content in different soil types, and to assess how this might impact crop contamination and environmental pollution. The results indicated that a change of the cropping system when the CLD content in the topsoil (0–0.3 m) drops below the threshold (1 mg CLD kg-1) established by local authorities to allow the cultivation of vegetable crops (e.g., cucumber, melon, watermelon, pumpkin), might cause crop contamination due to the presence of relatively high CLD levels in the subsurface layer (i.e., 0.3–0.6 m) of nitisols and ferralsols. The impact of changing the cropping system on the risk of environmental pollution depends on the time of that change, and it is much greater for vegetable crop systems established in the early 1990s following a financial crisis affecting the banana sector. This is linked to the progressive decline of SOC stocks caused by vegetable crop systems, which reduces CLD retention in the soil and increases CLD leaching. Overall, this study highlights the urgent need to include the monitoring of CLD in the subsurface layer and the dynamics of SOC stocks in current soil testing campaigns carried out on polluted soils in French Antilles