title: Chlordecone fate and mineralisation in a tropical soil (andosol) microcosm under aerobic conditions.
abstract: Chlordecone is a persistent organochlorine insecticide that, even decades after its ban, poses a threat to the environment and human health. Nevertheless, its environmental fate in soils has scarcely been investigated, and elementary data on its degradation and behaviour in soil are lacking. The mineralisation and sorption of chlordecone and the formation of possible metabolites were evaluated in a tropical agricultural andosol. Soil microcosms with two different soil horizons (S-A and S-B) were incubated for 215 days with 14C-chlordecone. At five different times (1, 33, 88, 150 and 215 days) the extractability of 14C-chlordecone was analysed. Mineralisation was monitored using 14CO2 traps of NaOH. The appearance of metabolites was studied using thin layer and gas chromatography techniques. At the end of the experiment, the water soluble 14C-activity was 2% of the remaining 14C-chlordecone for S-A and 8% for S-B. Only 12% of the remaining activity was non extractable and more than 80% remained extractable with organic solvents. For the first time to our knowledge, a significant mineralisation of chlordecone was measured in a microcosm under aerobic conditions (4.9% for S-A and 3.2% for S-B of the initial 14C-activity). The drastically lower emission of 14CO2 in sterilised microcosms indicated the biological origin of chlordecone mineralisation in the non-sterilised microcosms. No metabolites could be detected in the soil extracts. The mineralisation rate of chlordecone decreased by one order of magnitude throughout the incubation period. Thus, the chlordecone content in the soil remained large. This study confirms the existence of chlordecone degrading organisms in a tropical andosol. The reasons why their activity is restricted should be elucidated to allow the development of bioremediation approaches. Possible reasons are a heterogeneous distribution a chlordecone between sub-compartments with different microbial activities or a degradation of chlordecone by co-metabolic processes controlled by a limited supply of nutrients.
authors.affiliation: IRD, UMR LISAH Bât 24, 2 Place Viala, 34060 Montpellier cedex 1, France; INRA, UMR LISAH Bât 24, 2 Place Viala, 34060 Montpellier cedex 1, France. Electronic address: fernanje@supagro.inra.fr.
authors.forename: Jesus D
authors.initials: JD
authors.lastname: Fernández-Bayo
authors.forename: Carine
authors.initials: C
authors.lastname: Saison
authors.forename: Marc
authors.initials: M
authors.lastname: Voltz
authors.forename: Ulrich
authors.initials: U
authors.lastname: Disko
authors.forename: Diana
authors.initials: D
authors.lastname: Hofmann
authors.forename: Anne E
authors.initials: AE
authors.lastname: Berns
mesh_terms: D000332:Aerobiosis; D001673:Biodegradation, Environmental; D007631:Chlordecone / Q000737:chemistry*; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D013997:Time Factors; D014329:Tropical Climate
chemical_list: D012987:Soil; D007631:Chlordecone
keywords: ASE; Accelerated Solvent Extraction; Andosol; Chlordecone; ECD; Electron Capture Detector; FWI; French West Indies; GC-ECD; GC–MS; Gas Chromatography-Electron Capture Detector; Gas Chromatography–Mass Spectrometry; K(d); LSC; Liquid Scintillation Counter; Metabolites; Microcosm; Mineralisation; NER; Non Extractable Residues; OC; Organic Carbon; Organochlorine pesticides; R(f); Retardation factor; S; Soil; Soil sorption partition coefficient; TLC; Thin Layer Chromatography; d.w.e; dry weight equivalent