Soil Heavy Metal Concentrations and Leaf Accumulation in Four Subtropical Plant Species from South China

Abstract

Four common subtropical understory sun plants from South China, i.e., Euodia lepta (Spreng.)Merr. (EL), Ilex asprella Champ. (IA), Mussaenda pubescens Ait.f. (MP), and Rhodomyrtus tomentosa (Ait.) Hassk. (RT), were sampled and determined for leaf Cu, Zn, Cd, and Pb concentrations, with an aim to investigate geographic variations in leaf heavy metal concentrations and phytoaccumulation. Significant differences were found among the 4 sampling sites for soil pH and heavy metal concentrations of Zn, Cd and Pb, with higher acidity in the 3 sampling sites from the Pearl River Delta industrial area. However, leaf pH did not vary significantly among the geographic populations of El and MP. For leaf heavy metal concentrations, significant variations were observed among the geographic populations of El for Cd; IA for Zn, Cd, and Pb; MP for Cu, Zn, Pb, and Cd; RT for Zn and Pb. The mean Biological Accumulation Coefficients (BACs) of IA for Zn, Cd, and Pb were as high as 10.38 for Zn, 18.29 for Cd, and 1.76 for Pb, respectively. Coefficient of Variation (CV) of BACs for heavy metals among different geographic populations of each species ranged from 41.99~221.83%, indicating high geographic variability in phytoaccumulation of heavy metals, and their accumulation capacity declined with the increase of soil heavy metal concentrations. This study revealed that some particular populations of IA can serve as potential hyperaccumulators for Zn and Cd, while those of MP and RT as hyperaccumulators for Pb, and the toxicity and safety of RT and IA should be further studied and assessed.