The cup plant (Silphium perfoliatum L.) – a viable solution for bioremediating soils polluted with heavy metals

摘要

Heavy metal pollution, manifested by the accumulation, toxicity and persistence in soil, water, air, and living organisms, is a major environmental problem that requires energetic resolution. Mining tailing areas contain metal minerals such as Cu, Zn, Pb, Cr and Cd in high concentrations that pollute the environment and pose threats to human health. Phytoremediation represents a sustainable, long-term, and relatively inexpensive strategy, thus proving to be convenient for stabilizing and improving the environment in former heavy metal-polluted mining sites. This study presents the bioremediation potential of Silphium perfoliatum L. plants, in the vegetative stages of leaf rosette formation, grown on soil polluted with heavy metals from mining dumps in Moldova-Noua, in the Western part of Romania. The bioaccumulation factor (BAF), translocation factor (TF), metal uptake (MU) and removal efficiency (RE) of Cu, Zn, Cr and Pb by S. perfoliatum plants were determined in a potted experiment in controlled environmental conditions. The reference quantities of heavy metals have been determined in the studied soil sample. The experiment followed the dynamics of the translocation and accumulation of heavy metals in the soil, in the various organs of the silphium plants, during the formation of the leaf rosette (13-18 BBCH). The determination of the amount of heavy metals in soil and plants was achieved by the method of digestion with hydrochloric and nitric acid 3/1 (v/v) quantified by atomic absorption spectroscopy (AAS). The obtained experimental results demonstrate that the substrate has a high heavy metal content being at the alert threshold for Zn (260.01 mg kg -1 in substrate compared with alert threshold 300 mg kg -1 ) and at intervention thresholds for other metals (Cu -234.66 mg kg -1 /200 mg kg -1 ; 299.08 mg kg -1 /300 mg kg -1 and Pb-175.18 mg kg -1 /100 mg kg -1 ). The average concentration of the metals determined in dynamics in the dry biomass of plants varied between roots, petioles, and laminas. The root is the main accumulator for Cu and Cr (Cu – 37.32 mg kg -1 -13 BBCH to 43.89 mg kg -1 -15 BBCH and 80.71 mg kg -1 – 18 BBCH; Cr – 57.43 mg kg -1 – 13 BBCH to 93.36 mg kg -1 -18 BBCH), and for Zn and Pb the lamina seems to carry the same function. Preliminary results show that Silphium perfoliatum may be a viable alternative in the bioremediation and treatment of heavy metal-contaminated area.