Phytomanagement of chromium-contaminated soils using cannabis sativa (L.)

Abstract

This study aimed to assess whether hemp (Cannabis sativa L.) behaves as a Cr(III)-tolerant or a hyperaccumulator species and whether it could be a suitable species for the phytomanagement of Cr(III)-contaminated soils. The experiment was conducted in pots under greenhouse conditions comparing two fiber hemp (Fibranova and Carmagnola) and two seed hemp (Futura 75 and Fedora 17) varieties under four different soil Cr levels (24.3, 40.1, 55.8, and 87.4 mg kg−1) supplied with tannery sludge. The Cr level did not significantly influence hemp biomass production or Cr accumulation in the aboveground biomass. Focusing on marketable fractions, Cr uptake was 0.03 ± 0.04 mg plant−1 in the stems of fiber varieties and 0.60 ± 0.17 mg plant−1 in the seeds of seed varieties. The only significant accumulation of Cr content was indeed observed in the root system, where it reached 0.63 mg plant−1 for the fiber varieties and 1.76 mg plant−1 for the seed varieties in the fertilization with 200% N by tannery sludge (T200) treatment. The Cr translocation factor (aboveground-to-belowground biomass) decreased from 2.17 to 0.37, increasing the Cr level applied from 24.3 to 87.4 µg g−1. The maximum Cr concentrations in aboveground biomass fractions (average value of 40.4 mg kg−1) were found in the seeds, regardless of treatment. The low Cr content in the aboveground biomass suggests that hemp can be considered an excluder species, valid as a candidate for Cr-contaminated soils’ phytomanagement.