Interactions between heavy metals and other mineral elements from soil to medicinal plant Fengdan (Paeonia ostii) in a copper mining area, China

In order to analyze the interaction relationship between heavy metals and other mineral elements during the processes of absorption and translocation by plant grown on heavy metal-contaminated area, the concentrations of Cu, Zn, Mn, Cd, Pb, Ca, Mg, Fe, and K in the medicinal plant Paeonia ostii T. Hong et J. X. Zhang and its rhizospheric soil were determined, which grow around an abandoned copper tailings reservoir in Tongling City, China. Geo-accumulation index (I_geo) calculation indicated that Cu and Pb are the main pollution elements in the rhizospheric soil. Moreover, the Cu and Pb concentrations in the cortex moutan of P. ostii exceeded the maximum permissible limits for food product safety. The bioaccumulation factor values of the tested metals in plant roots were found < 0.50, with the exception of Ca (maximum 5.99). The translocation factor values of detected heavy metals Cd and Pb were more than 1.00, which indicated that P. ostii could be considered a potential accumulator plant for Cd and Pb. Significant positive correlations including Cu-Cd, Cu-Zn, Cu-Pb, Cd-Zn, Cd-Fe, Cd-Fe, Zn-Pb, Pb-Fe, Mn-Fe, and Ca-Mg in the cortex moutan and Cu-Zn, Cu-Fe, Zn-Mg, Zn-Fe, and Mn-K in the leaves were observed (P < 0.05). Significant positive correlation between Cu, Zn, Mg, and Fe was also confirmed in the processes of absorption and translocation from the soil to plant (P < 0.05), which evidenced that synergistic element interactions of the essential elements Cu, Zn, Mg, and Fe are a result of the similarity in their ionic radii and octahedral coordination geometry.