Bioaccumulation of heavy metals in earthworms from field contaminated soil in a subtropical area of China

Bioaccumulation factors for heavy metals (Cd, Zn, Cu, and Pb) were examined for selected earthworm species (Metaphire californica, Amynthas homochaetus, Amynthas pecteniferus, and Amynthas heterochaetus) that inhabit metal-polluted soils in a subtropical area (Hunan Province) of South China. The earthworms had high plasticity in inhabiting in situ contaminated areas and showed high uptake of the heavy metals and capability for their accumulation in the tissues. The bioaccumulation factor (BAF) were greatest for cadmium and ranked as follows: Cd (10.6-18.8) >> Zn (1.15-1.75) > Cu (1.01-1.35) > Pb (0.56-0.95). Earthworm species with the similar BAF of heavy metals (p > 0.05) belong to the same ecological group. Within individual groups, Cd, Cu, Zn, Cu, and Pb concentrations in earthworms are consistently predicted by total and extractable fraction (DTPA-extractable) in soil. Our results provide insights into the ecological relationships and variations in the uptake and accumulation of heavy metals in different earthworm species in contaminated soils in China.