Distribution characteristics and potential ecological risk assessment of heavy metals (Cu, Pb, Zn, Cd) in water and sediments from Lake Dalinouer, China

• The transport behaviors of heavy metals in water are studied and discussed.
• First carry out the study of AVS–SEM in sediment under high alkalinity condition.
• Find out the key factor in controlling bio-available fractions of Cu, Pb, Cd and Zn.
• Several methods are applied to assess potential ecological toxicity of heavy metal.

The concentrations of Cu, Pb, Zn and Cd were measured in water and sediment to determine their distribution characteristics and potential ecological risks of the Lake Dalinouer. The results revealed that the dominate form of Cu, Pb, Cd and Zn in surface sediments respectively were organic sulfides, Fe–Mn oxides, carbonates and Fe–Mn oxides, with a mean content of 4.28 mg kg−1, 0.76 mg kg−1, 7.84 μg kg−1 and 1.77 mg kg−1, respectively; the concentrations of bio-available metals had an increase tendency from the northeast to the southwest part of this lake. Acid volatile sulfides (AVS) and simultaneously extracted metal (SEM) were used to predict the potential bioavailability of heavy metals. The horizontal distribution of AVS (0.15–2.4 μmol g−1, mean 0.53 μmol g−1) in surface sediments shows an increasing trend from southwest to northeast of the lake, whereas SEM (0.02–0.99 μmol g−1, mean 0.37 μmol g−1) had an opposite pattern. The relative high salt and pH which restrained the bioactivities of sulfate-reducing bacteria (SRB) were the main controlling factor in AVS concentrations. The vertical variation of AVS concentration in sediment core increased with depth and different from SEM. Potential ecological risk index (PERI) and geo-accumulation index (Igeo) were used to assess heavy metals accumulation. The results indicated that moderate contamination of most heavy metals was prevalent and presented a decreased trend from southern to northern of the lake, and element Cd emerged the greatest potential ecological risk. The pollution of heavy metal in the southern of the Lake Dalinouer should be taken into consideration seriously.

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