Industrial hemp (Cannabis sativa L.) in a phytoattenuation strategy : remediation potential of a Cd, Pb and Zn contaminated soil and valorization potential of the fibers for textile production

In past studies, industrial hemp (Cannabis sativa L.) has been shown to tolerate stress from heavy metals and to accumulate the metals in its tissues. Nonetheless, up to now, it remained unclear whether hemp grown on contaminated soil could be safely used in the textile industry and integrate a phytoattenuation strategy. A growth experiment was set up to screen 6 hemp cultivars for their ability to take up heavy metals in the different plant parts when grown on soil contaminated with Cd, Pb, and Zn. The potential safe use of the produced biomass in comparison to industrial quality guidelines, especially the fibers, was analyzed. Plant tissues show different patterns of Cd, Pb, and Zn uptake and it could not be stated that one plant part accumulates a higher amount of all elements compared to the others. While Pb and Zn concentrations followed the trend leaves>shives>fibers, Cd was mostly concentrated in the fibers. The lowest concentrations in fibers were found in the early cultivars USO 31 and Bialobrezskie respectively for Cd (0.59 +/- 0.15 mg/kg) and Pb (1.6 +/- 0.7 mg/kg), and in the semilate cultivar Dacia Secuieni for Zn (7.2 +/- 1.4 mg/kg). The late cultivar Carmagnola Selected displayed the highest concentrations for Cd (1.7 +/- 0.5 mg/kg) and Zn (13 +/- 2 mg/kg), as the early cultivar USO 31 did for Pb (11 +/- 1 mg/kg). Nevertheless, both Cd and Pb concentrations in the fibers were far below the heavy metal thresholds for textile product safety in all cultivars, while Zn is not considered toxic in textile production. In addition, low Pb, Cd, and Zn concentrations in the shives suggest the potential safe use of this residual fraction of hemp fiber production as well. These results are promising in terms of safe use of the produced hemp fibers in the textile industry and thus of the potential valorization of contaminated land through hemp cultivation and the development of non-food value chains within a phytoattenuation strategy