Phytoremediation Potential of Hemp in Metal-Contaminated Soils: Soil Analysis, Metal Uptake, and Growth Dynamics

The remediation of soils contaminated with heavy metals and radionuclides remains a significant environmental challenge. This study evaluated the phytoremediation potential of industrial hemp (Cannabis sativa L.) in soil collected from a historical evaporation dam, characterized by high levels of diverse metals, including Al, Cr, Fe, and radioactive elements (U, Th). Three treatments were applied: a control, a metal-spiked treatment (chelated with citric acid), and an NPK + spike treatment. A separate six-month greenhouse trial compared plants grown with and without NPK nutrients. Results demonstrated that the addition of a chelating agent significantly enhanced the bioavailability and subsequent uptake of key metals, including U, Se, and Pd. NPK fertilization combined with chelation resulted in the greatest plant biomass (≈4.5 g) and height (>18 cm), which correlated with higher total metal accumulation. Bioaccumulation factors (BAF > 1) were highest for B, Sr, Cd, and Bi, with values for Cd and U reaching 1.3 and 2.1, respectively. Foliar analysis revealed that leaves accumulated significantly higher metal concentrations than stems (e.g., Translocation Factor (TF) ~ 2.0 for Cd, Pb, and U), acting as the primary sink. This study concludes that hemp, particularly when assisted with chelating agents and adequate nutrition, is a highly effective candidate for the phytoremediation of multi-metal contaminated soils. The NPK + chelation strategy is the most promising for maximizing both biomass production and metal extraction efficiency.