Metal concentrations in sediments and tilapia collected from inland waters of Hong Kong

Abstract

This paper presents data on the concentrations of six heavy metals, copper (Cu), zinc (Zn), lead (Pb), nickel (Ni), cadmium (Cd) and chromium (Cr), in sediments and fish sampled from inland waters of Hong Kong. Sediments and tilapia ( Tilapia mossambica) were collected from Shing Mun River (at Fo Tan, Tai Wai and Siu Lek Yuen), Lam Tsuen River (at Tai Wo) and Tai Po River (at Tai Po), as well as from a commercial fish pond (at Mai Po) for comparison. The total concentrations of the six metals in river sediments were significantly ( p<0.05) higher than those collected from the fish pond. The highest metal concentrations of Cu, Zn, Ni, Cd and Cr were recorded in the sediment of Fo Tan at Shing Mun River, with the values of 449, 1220, 67.0, 4.03 and 85.4 mg kg −1 (dry weight), respectively. On average, the total metal contamination in sediments followed the order of Fo Tan>Tai Wai>Tai Wo>Siu Lek Yuen>Tai Po>Mai Po. Different metals seemed to accumulate in different organs of fish (muscle, gill, skin and viscera). A substantial amount of heavy metals was observed in tilapia which lived in contaminated environment (Fo Tan and Tai Wai), when compared to those collected from the fish pond. Tilapia collected from Fo Tan contained the highest concentrations of Cu (168 μg g −1) and Zn (266 μg g −1). Significant relationships ( p<0.05) between metals in different chemical fractions (exchangeable, carbonate, Fe–Mn oxide, organic and residual) of sediments and metals in fish organs (Cu in viscera, Zn in skin, Pb in all organs and Cr in muscle) were found.