Occurrence and risk assessment of heavy metals in water, sediment, and fish from Dongting Lake, China

Abstract

In this study, 15 representative surface waters and sediments and seven typical fish were collected during the wet season in 2016 to explore the occurrence, chemical fractionation, and ecological risk of heavy metals (Cu, Zn, Pb, Cd, Cr, Hg, As, and Ni) in aquatic ecosystems of Dongting Lake in China. In surface water, the concentrations of all elements were lower than the third grade of the surface water quality standards (GB3838-2002). The highest concentrations of Zn, Pb, Cd, Ni, and Cu were found in the outlet of Dongting Lake, whereas As and Cr were highest in the Xiangjiang River Delta area. In surface sediments, the concentration decreased in the order of Zn > Cr > Pb > Cu > Ni > As>Cd > Hg; the highest concentration of all elements, except for Hg, was located in the Xiangjiang River Delta area; for chemical fractionation, Cr, Hg, Zn, As, Ni, and Cu were mainly residual fractionation; and Pb and Cd were mainly in a reducible state and fraction soluble in acid, respectively. In fish muscle, the concentrations of all elements were lower than relevant standards; the highest concentration appeared in fish living in the middle-lower and demersal layers. As for the feeding habits of fish, the average concentration decreased in the order of carnivorous > omnivorous > herbivorous fish. The potential ecological risk and the ratio of secondary phase to primary phase assessment showed that Cd and Hg had the highest ecological risk and that Cd and Pb had a high risk of secondary release. A health risk assessment showed that drinking water and fish for consumption in urban and rural areas around Dongting Lake were in the acceptable level.