Occurrence, distribution, and risk assessment of the metals in sediments and fish from the largest reservoir in China

Abstract

The concentrations, distribution, and ecological risk assessment of the metals (Cr, Ni, Cu, Zn, Cd, Pb, As, and Hg) in sediments and fish were investigated in the mainstream and tributaries of the Three Gorges Reservoir (TGR) after a submergence period. The results showed that the metal levels in the sediments were above the geochemical background values of the Yangtze River, especially for Cd, which was 9.5-fold higher than the local soil background. The mean concentrations of As and Cd showed a significantly increasing tendency in the TGR after submergence. However, the mean concentrations of these metals were lower than the probable effect concentrations. The metal concentrations in the sediments from the mainstream were higher than those in the tributaries. The geoaccumulation index showed that Cr, Ni, and As were at uncontaminated levels, while Cu, Zn, Pb, and Hg were at uncontaminated to moderately contaminated levels, and Cd was at the moderately contaminated levels. The pollution level of the metals was in the order of Cd > Hg > Zn > Pb > Cu > As > Ni > Cr. The assessment of the potential ecological risk index of the metals suggested that the TGR exhibited low to moderate ecological risk in the sediments, with Cd and Hg as the predominant elements. Health risk analysis of the individual metals in the fish indicated that the total target hazard quotient for the general population did not exceed 1, demonstrating no evidence of unacceptable health risk to the residents' consuming TGR fish.