Concentrations of toxic metals and ecological risk assessment for sediments of major freshwater lakes in China

• Systematic sediment geochemical surveys in 150 Chinese lakes were surveyed.
• Levels of trace metals and degree of ecological risk in 21 lakes were widely compared and discussed.
• Mercury was ranked as presenting the greatest ecological risk, followed by Cd and As.
• Dianchi and Dongting Lakes may be some of the most seriously contaminated lakes.
• Numerous adverse effect areas above the PEC were delineated.

A systematic geochemical lake sediment survey has been carried out in major freshwater lakes in China. Surface lake sediment (0–20 cm) at a density of 1 sample/4 km2 and deep lake sediment (150–180 cm) at a density of 1 sample/16 km2 were collected and analyzed with standard procedures. This overview provides a current ecological risk assessment for toxic metal contamination (As, Cd, Cr, Cu. Hg, Ni, Pb, and Zn) in the surface sediments of major freshwater lakes in China. Lake sediment in China poses a moderate ecological risk on a nationwide basis using a potential ecological risk index (PERI). Mercury ranked as presenting the greatest ecological risk, followed by Cd, As, Pb, Cu, Ni, Cr, and Zn. Liangzi Lake was classified as having high ecological risk; Dalonghu Lake, Dianchi Lake, Dongting Lake, Fuxian Lake, and Qilu Lake as having moderate ecological risk; while the other surveyed lakes were classified as having low ecological risk. Uncertainties of risk assessment are also discussed by considering geochemical background, the eco-toxicity of metals and the sensitivities of local benthic communities. These comprehensive findings have provided valuable information for improvement of lake management and pollution prevention and control in China.