[Biomagnification of heavy metals in the aquatic food chain in Daning River of the Three Gorges Reservoir during initial impoundment].

Heavy metals have been accumulated in sediment after impoundment in the Three Gorges Reservoir (TGR). In order to evaluate the risk of biomagnification of heavy metals, we investigated the trophic relationships and heavy metal concentrations in fish from a tributary within TGR. Sixteen fish species were collected from Daning River, and concentrations of eight heavy metal elements (Cr, Ni, Cu, Zn, Pb, Cd, As, and Hg) were determined, as well as the ratios of stable carbon and nitrogen isotopes. Results showed that most heavy metal concentrations were low in TGR, but changed significantly among different species. The delta13C values varied significantly among different groups (-22. 80 per thusand - 28. 97 per thusand) ; while the delta15N values (6. 41 per thusand - 13. 88 per thusand) varied based on their feeding types. A significantly trophic level-dependent increase was found in concentrations of Hg, indicating an overall biomagnification of Hg; but the increase of Hg concentration per trophic level was lower than that in previous studies. No tendency towards trophic-level enrichment was observed for other elements studied. However, a much higher heavy metal concentration was observed in small-sized fish samples, indicating a potential risk in environment.