Phytoremdiation of chlordecone polluted soils of French West Indies – CLDPhy

Chlordecone (CLD) is an organochlorine insecticide used in the French West Indies from 1973 to 1993 to control the banana weevil. It is now classified as a persistent organic pollutant (POP) and pollutes in a sustainable way the agro-ecosystems (soils and waters) of the French West Indies: from banana plantations to the coastal waters constituting a risk for the environment. It also leads to the contamination of plant and animal foodstuffs as well as fishery products. This contamination of food is the main source of contamination by CLD of the West Indian population and constitutes a high chemical health risk for this population.
It is therefore necessary to remediate polluted environment, even if management measures have been taken to reduce the risks. Many studies have been carried out to reduce this pollution. They used chemical processes such as the CLD reduction by zero-valent iron (ISCR method) or microbiological methods. None of them has resulted in methods that can be used on large polluted areas (between 15 and 25% of the agricultural area of the French West Indies), either because their cost would be too high or because of their lack of efficiency. One solution that we propose to study in this project remains unexplored for the moment: the phytoextraction.
This is based on the capacity of some plants to absorb CLD and to transfer it into their above-ground parts, which are then harvested for ex-situ treatments. The other phytoremediation processes cannot be used cause to CLD degradation resistance. In order not to introduce exogenous plants, CLD? will focus on West Indian plants.
At first, CLD? will carry out a survey of plant species growing in the OPALE observatory watersheds in Guadeloupe and determine their contamination rate in CLD, ß-hydro-CLD and chlordecol. In parallel, studies under controlled conditions will determine: on the one hand, whether CLD accumulates in the wood of woody plants, a sine qua non for their use in phytoremediation to avoid a futile cycle of remediation by export of CLD to the foliage; On the other hand, the relationship between the rate of CLD accumulation, the evapotranspiration rate (CLD vector in plants), and the isotopic discrimination of carbon (d13C) will be studied. The latter is more easily determined than the in-situ measurement of the evapotranspiration rate of one plant. These studies will refine the criteria for screening plants potentially with the best CLD phytoextraction capacity.
In a second phase, tests on contaminated sites and in lysimeter box will allow testing, under realistic conditions of use, the capacity of the selected plants to decontaminate the soil. In addition, cultivated plants (outside of any agronomic use) will be tested. They rapidly form a high biomass and are therefore susceptible to rapid CLD accumulation. The final goal of these tests and CLD? will be to provide a list of plants that can be used in various phytomanagement situations adapted in particular to cultivated areas, for example in co-culture, and to Creole Gardens.
CLD? fits in with some of the research axes of PNAC III. However, in order to meet the requirements of PNAC IV, recently edited, concerning the newly identified metabolites of CLD in the environment, two additional tasks (creation of sample banks) will be set up in order to valorize, in the future, the polluo-floristic survey carried out on OPALE by the analysis of these new metabolites and the microbial consortia likely to have formed them. Finally, this project based on studies carried out in Guadeloupe is of course intended to be applicable to the whole French West Indies.