No abstract

Phytoattenuation combines phytoextraction or phytostabilization with the economic valorization of the biomass produced on the contaminated soil. Sorghum bicolor is a suitable crop for this strategy, as it is known to be metal-tolerant and can be used for biogas or bioethanol production or in strategies toward biofortification. In the current investigation, two cultivars, Biomass 133 and Trudan Headless (HL), were studied in a metal-contaminated (Cd, Pb, Zn) field site located in northern France to assess their potential use in a phytoattenuation strategy. The biomass yield and the metal transfer in the produced biomass were monitored in three plots with different pollution levels. Both cultivars were tolerant to high levels of metal pollution in field conditions, with yields similar to that obtained on uncontaminated sites. Neither of the cultivars changed the metal mobility of the soil and both exhibited a metal-excluder behavior. Nevertheless, Cd concentration in the aboveground part of Trudan HL, and of Biomass 133 to a lesser extent, could restrict their use in some valorization options. However, biogas production was possible with the produced biomass, indicating anaerobic digestion to be a possible valorization route for sorghum grown on contaminated sites.

Phytomanagement uses plants and soil conditioners to create value on contaminated land while minimising environmental risk. This work was carried out on a metal(loid)-contaminated site and aimed at assessing the suitability of Salvia sclarea L. (sage) and Coriandrum sativum L. (coriander) combined with an Arbuscular Mycorrhizal Fungus (AMF) inoculant to immobilise metal(loid)s and produce essential oils (EO). The effect of the inoculant on the transfer of metal(loid)s (ML, i.e. Cd, Cu, Pb, Zn, As, Ni, and Sb) to plants and the ML soil mobility were investigated. The ML concentrations in EO from both plant species and the valorisation options for the distillation residues (soil conditioner, animal fodder, and anaerobic digestion) were studied. Sage was a suitable candidate for this value chain because it presents an excluder phenotype and the residues of oil extraction could be used as a soil conditioner. The metal concentrations in the sage EO were similar to those obtained from plants cultivated on an uncontaminated soil. These results indicate the suitability of sage harvested on the contaminated soil according to the ML fate in the whole value chain. Like the EO of sage, ML concentrations in the coriander 2 EO did not differ from those in the commercial EO that were obtained from plants grown on uncontaminated soil.However, the use of distillation residues of coriander was limited by their relatively elevated Cd concentrations.The use of a mycorrhizal inoculum did not decrease the Cd mobility in soil for the coriander.

The study of different possible biomass valorization routes is crucial in order to diversify phytomanagement options, allowing the landowner/stakeholder to choose the best option based on site characteristics and the benefits of local value chains. In the current study, field and laboratory experiments were conducted to assess the suitabilitity of Malva sylvestris L. for the phytoattenuation of a dredged sediment disposal site contaminated with trace elements (trace element (Cd, Cu, Pb, and Zn). The selected crop was Malva sylvestris, a flowering plant from which a colourant can be extracted to be used in dying of textiles as a way to valorize the produced biomass grown on this contaminated land. Under the conditions of the investigated site, the analysis of TE in the sediment and the biomass matrix showed no effect of M. sylvestris on the sediment TE contamination mobility with an excluder phenotype (Bioconcentration factor < 1). Metal concentrations were found to be the highest in the leaves followed by in the stem and flower. The dye extract obtained from the flower part of M. sylvestris permitted the silk alum-pretreated fabric to be dyed yellow, and the TE concentration in the dyed textile fabrics respected the threshold values set by OEKO-Tex standard 100.