Mobility, binding behavior and potential risks of trace metals in the sediments of the fifth largest freshwater lake, China

The trace metal pollution of sediments in Chaohu Lake, one of the most highly eutrophic lakes in East China, was investigated. Surface sediment (0–5 cm) samples were collected from 35 different positions and analyzed by inductively coupled plasma optical emission spectrometry to determine trace metal contents. Results showed that the mean content of trace metals was as follows: Cr, 85.09 mg kg⁻¹; Cu, 34.49 mg kg⁻¹; Ni, 26.46 mg kg⁻¹; Pb, 34.17 mg kg⁻¹ and Zn, 107.46 mg kg⁻¹. The trace metal concentrations from different sampling sites displayed spatial diversity; the heavily polluted sampling sites were close to where estuaries flow in to the lake. A four-step sequential extraction was used to examine the partitioning of the trace metals. Results demonstrated that the percentage of the species bound to the oxidizable phase for all trace metals ranged from 15.6 to 37.7%, while for Cu, Cr and Ni, the main forms were residual (41.3, 62.3 and 69.8%, respectively). Trace metals in the oxidizable fraction may mainly exist in the form of sulfides. The ecological potential risks of trace metals decreased as follows: Pb > Zn > Cu > Cr > Ni.