Reduction of chlordecone environmental availability by soil amendment of biochars and activated carbons from lignocellulosic biomass

Abstract

Chlordecone (kepone or CLD) was formerly used in French West Indies as an insecticide. Despite its formal ban in 1993, high levels of this pesticide are still found in soils. As such, sequestering matrices like biochars or activated carbons (ACs) may successfully decrease the bioavailability of halogenated compounds like CLD when added to contaminated soils. The present study intends (i) to produce contrasted sequestering matrices in order to (ii) assess their respective efficiency to reduce CLD environmental availability. Hence, the work was designed following two experimental steps. The first one consisted at producing different sequestering media (biochars and ACs) via pyrolysis and distinct activation processes, using two lignocellulosic precursors (raw biomass): oak wood (Quercus ilex) and coconut shell (Cocos nucifera). The chemical activation was carried out with phosphoric acid while physical activation was done with carbon dioxide and steam. In the second step, the CLD environmental availability was assessed either in an OECD artificial soil or in an Antillean contaminated nitisol (i.e. 2.1 µg CLD per g of soil Dry Matter, DM), both amended with 5wt% of biochar or 5wt% of AC.

Assessment of an NDL-PCBs Sequestration Strategy in Soil Using Contrasted Carbonaceous Materials through In Vitro and Cucurbita pepo Assays

“…For AC materials, AC2 and AC3 were the most effective in reducing PCB concentrations given their larger specific surface area and mesoporous surface, while AC1 was less effective due to its granular shape. This result confirms that surface properties and textural characteristics impact the sorption properties of carbonaceous materials in contaminated soils [11,12,14,26,27]. Regarding the type of pollutants, no difference could be shown in terms of sequestration efficiency by the different carbonaceous materials probably because the physicochemical properties related to adsorption in soil such as lipophilicity are of the same order (about log Kow of 7).…”

“…A possible strategy to reduce this halogenated POP transfer to vegetal is to trap them in the soil by making them non-available. In this perspective, several amendment materials have already been evaluated and proven to be effective to limit the POP transfer, as assessed on root vegetables [9,10] or through an in vitro assay [11,12]. To limit transfer to plant, compost amendment of chlordecone (CLD) contaminated soils displayed a reduction of transfer to root vegetables by a factor of 3 to 10 compared to non-amended soils [13].…”

“…However, such data is lacking for other POPs, and also for plants known to accumulate halogenated POPs inside their aerial parts like Cucurbitaceae family. Activated carbons (ACs) amendment showed also a reduction up to 90% in non-physiological based in vitro environmental availability assays [12,14]. Some studies reported the ability of activated carbons and biochars to trap and reduce the transfer of pesticides, PCBs and other organic pollutants in cucurbits [15][16][17][18][19].…”

Effects of mixtures containing chlordecone and a dechlorinated by-product on hydra regeneration capacity: use of experimental design to evaluate the toxicity risk associated with remediation programs in long-lasting polluted areas

“…To face this situation, soil remediation programs have been proposed since soil is the main source of contamination of all the other FWI ecological compartments. Some of these programs suggest adding CLD adsorbents to the soil (activated carbon, biochar, compost) to decrease or eliminate CLD transfers to water, crops, and breeding animals (Clostre et al 2014b;Ranguin et al 2020), to extract CLD from soil with plants (Liber et al 2018) or to destroy CLD by microbial or physicochemical processes (Chevallier et al 2019;Lomheim et al 2020;Macarie et al 2016;Mouvet et al 2017). To date, among all these approaches, beside the addition of compost, the physicochemical In Situ Chemical Reduction (ISCR) process, which consists of adding Fe 0 to the soil, is the only one to have been tested with some success under real environmental conditions in FWI, up to the plot scale (Mouvet et al 2020).…”

In vitro and in vivo assessment of a CLD sequestration strategy in Nitisol using contrasted carbonaceous materials

“…One possible strategy to reduce this CLD transfer to animals is to sequestrate it within the soil matrix. In this perspective, several amendment sources have already been evaluated and proven to be effective to limit the CLD transfer, as assessed using plants (Fernandes et al, 2010;Woignier et al, 2015Woignier et al, , 2012 or through an in vitro assay (Ranguin et al, 2020) and confirmed in animal studies using artificial soils (Delannoy et al, 2019;. To limit transfer to plant, compost amendment of CLD-contaminated soils displayed a reduction of transfer to plants by a factor of 3 to 10 compared to non-amended soils (Woignier et al, 2012).…”