Concentration of chlordecone and its main transformation products in endogeic and epigeic earthworms along two contamination gradients on Nitisol and Andosol

Chlordecone (CLD), an organochlorine insecticide formerly applied in the Lesser Antilles, was banned more than thirty years ago. Because of its exceptional persistence, it continues to contaminate soils and organisms. The consequences for earthworms have been poorly studied despite the key role they play in soil functioning. This study aimed to assess the contamination of endogeic ( Pontoscolex corethrurus ) and epigeic earthworms by chlordecone and its main transformation products (chlordecol, 10-monohydrochlordecone [A1] and 8-monohydrochlordecone [A2]) along two contamination gradients, on Nitisol and Andosol. Twenty-four banana fields were sampled, with soil concentrations ranging from the limit of quantification to 2280 μg.kg -1 . At similar concentration levels, earthworms showed higher levels of contamination in nitisols, suggesting that chlordecone is more bioavailable in this soil type than in andosols. The endogeic species P. corethrurus significantly bioaccumulated CLD, with whole-body concentrations averaging, respectively, 18 and 13 times the concentrations measured in the Nitisol and the Andosol. Bioaccumulation in this endogeic species was 8 times greater than in the epigeic earthworms . Since CLD bbioaccumulation factor increased in earthworms with an increasing soil concentration, very hight levels of earthworms contamination could be expected in fields where the concentration exceeded the range covered in this study. Furthermore, A1 and A2 were not quantified in any of the soil samples but were quantified in earthworms (10 and 47% of endogeic samples, respectively). Because of its high capacity to bioaccumulate chlordecone and its ubiquitous distribution, we propose using P. corethrurus as a bioindicator of soil contamination by chlordecone and its transformation products, particularly when technical limitations prevent the reliable measurement of low concentrations of these molecules in soil.