Affiliations: Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong | Institute for Natural Resources and Waste Management, and Department of Biology, Hong Kong Baptist University, Kowloon Tong, Hong Kong
Abstract: Concentrations of 8 heavy metals: cadmium (Cd), copper(Cu), zinc (Zn), lead (Pb), nickel (Ni), chromium (Cr), antimony (Sb) and tin (Sn) were examined in 3 species of bivalves (Pernaviridis, Crassostrea rivularis and Ruditapes philippinarum) collected from 25 sites along the Pearl River Delta coastal waters in the South China Sea from July to August 1996. In general, Cd, Cu, Zn and Sn concentrations in the three bivalve species collected from the Estuarine Zone were significantly higher than those collected from the Western and Eastern Zones of the Pearl River Delta, which are related to the existence of various anthropogenic activities in the catchment of the Pearl River Delta. The Western Estuarine Zone is mainly impacted by Cr, Ni and Cu contamination. In Victoria Harbor, heavy metal contamination is mainly due to Cuand Pb. Cd, Cu and Zn concentrations in oysters were significantly higher than those in mussels and clams. This could be explained by the fact that oysters live mainly in the Estuarine Zone of the Pearl River Delta which receives most of the polluting discharges from the catchment of the Delta. During turbid condition, heavymetals (soluble or adsorbed on suspended particulates) discharged from the Delta are filtered from the water column and subsequently accumulated into the soft body tissues of oysters. Heavy metal concentrations in the three bivalve species were compared with the maximum permissible levels of heavy metals in seafood regulated by the Public Health and Municipal Services Ordinance, Laws of HongKong, and it was revealed that Cd and Cr concentrations in the three bivalve species exceeded the upper limits. At certain hotspots in the Delta, the maximum acceptable daily load for Cd was also exceeded.
Keywords: heavy metals, oyster, mussel, clam, coastal waters