The Use of Sorghum in a Phytoattenuation Strategy: A Field Experiment on a TE-Contaminated Site

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 of a Trace Element-Contaminated Site to Produce a Natural Dye: First Screening of an Emerging Biomass Valorization Chain

“…The agronomic parameters and the total TE concentration in the sediment (Table 1) of the three areas were already presented and discussed in earlier research [18]. The agronomic parameters showed a fine sediment texture on the three areas, with a pH of around 8.…”

“…TE concentration analyses of the sediment exhibited a high degree of contamination in this site. On three areas, an experimental setup with nine plots of 25 m 2 per area (Area 1, Area 2, Area 3, Figure 1) was devised in April 2019 to assess the applicability of different plant species for phytomanagement [18]. To reduce herbivory damage, the plots were protected by a 2 m high fence, which was buried down to 50 cm below ground.…”

“…The experimental site was a former dredged sediment disposal site located in Fresnes-sur-Escaut (Hauts-de-France, France; 50°25'41.1" N 3°35'01.9" E) [18,35]. Between 1978 and 1989, this site received sediment from dredging activities on rivers and canals.…”

“…As described in Perlein et al [18], two sediment sampling moments were performed during the experiment, one just before sowing and the second at harvest. The samples were collected with a hand auger, which permitted the sampling of the first 20 cm of the sediment depth.…”

“…The diversity of the plant species involved in phytomanagement (e.g., trees, industrial crops, herbs, and aromatic plant) could allow biomass valorization as a material (fibers, essential oil, eco-catalyst) or as an energy source (combustion, biogas, bioethanol) [6,[10][11][12][13][14][15][16][17][18][19]. These non-food purposes might be integrated into the biobased market and can contribute to its development.…”