Abstract
To restore and clean up polluted soils, aided phytoremediation was found to be an effective, eco-friendly, and feasible approach in the case of many organic pollutants. However, little is known about its potential efficiency regarding polychlorinated dibenzo-p-dioxins and furans-contaminated soils. Thus, phytoremediation of aged dioxins/furans-contaminated soil was carried out through microcosm experiments vegetated with alfalfa combined with different amendments: an arbuscular mycorrhizal fungal inoculum (Funneliformis mosseae), a biosurfactant (rhamnolipids), a dioxins/furans degrading-bacterium (Sphingomonas wittichii RW1), and native microbiota. The total dioxins/furans dissipation was estimated to 23%, which corresponds to 48 ng.kg−1 of soil, after six months of culture in the vegetated soil combined with the four amendments compared to the non-vegetated soil. Our findings showed that the dioxins/furans dissipation resulted from the stimulation of soil microbial enzyme activities (fluorescein diacetate hydrolase and dehydrogenase) and the increase of bacterial abundance, richness, and diversity, as well as fungal diversity. Amplicon sequencing using Illumina MiSeq analysis led to identification of several bacterial (Bacillaceae, Sphingomonadaceae) and fungal (Chaetomium) groups known to be involved in dioxins/furans degradation. Furthermore, concomitant cytotoxicity and dioxins/furans concentration decreases were pointed out in the phytoremediated soil. The current study demonstrated the usefulness of combining different types of amendments to improve phytoremediation efficacy of aged dioxins/furans-contaminated soils.
Highlights
Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzo-furans (PCDF) are persistent chlorinated organic compounds, ranked among the priority environmental contaminants in the world [1]
Whereas no arbuscular mycorrhizal fungi (AMF) structures were observed in the absence of inoculation, mycorrhizal hyphae, arbuscules, and vesicles were clearly observed in roots of alfalfa inoculated with F. mosseae
In order to investigate the potential of aided phytoremediation in cleaning-up aged PCDD/F contaminated soil, a microcosm experiment using alfalfa associated with several biological amendments
Summary
Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzo-furans (PCDF) are persistent chlorinated organic compounds, ranked among the priority environmental contaminants in the world [1]. Some studies have shown that environmentally friendly biosurfactants such as rhamnolipids have the ability to effectively solubilize and mobilize organic compounds adsorbed on soil particles [19] These amphiphilic compounds have many advantages over synthetic surfactants in remediation for contaminated soils, such as non-toxicity and high biodegradability [20]. Some investigations showed that AMF can contribute to increase the biodegradation of chlorinated pollutants such as polychlorinated biphenyls in the plant rhizosphere [23,24] Another way to enhance phytoremediation efficacy relies on the improvement of the degradative capacity of contaminated soil through the introduction of a specific strain or microbial consortia [25]. This strategy has proven to be successful in cleaning up hydrocarbon-polluted soil [24] but no data are available regarding its efficiency in PCDD/F-contaminated soil bioremediation
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