An overview of trace metal pollution in the coastal waters of Hong Kong.

The state of metal pollution in Hong Kong's coastal waters has been assessed by measuring metal levels in: (i) the water column; (ii) sediments and (iii) in organisms, i.e. biomonitors. Current literature is reviewed. Data from sediment analysis have shown that metal pollution is most severe in the urban areas of Victoria Harbour, Tolo Harbour, Deep Bay and Northwestern waters. Bottom sediments in typhoon shelters are particularly heavily polluted with, for example, Cu levels from Kowloon Bay reaching 5300 mg.kg-1 in 1995. Since 1987, levels of pollution have generally either stabilized or fallen in Deep Bay and Victoria Harbour but have increased in Inner Tolo Harbour and Northwestern waters. Many biomonitors have been used to study metal pollution in Hong Kong, the most popular of which are barnacles, mussels (in particular Perna viridis) and algae (in particular Ulva lactuca). Biomonitoring studies generally recorded high levels of metal pollution in Victoria Harbour in the late nineteen seventies and early eighties, with increasing pollution of the semi-enclosed Tolo Harbour through the eighties and early nineties. In a recent study using barnacles, the levels of Ag, As, Cd, Cu, Hg, Pb and Zn were shown to be greatly reduced as compared to those recorded in 1986 and 1989, respectively. Levels of metal pollution in Hong Kong coastal waters may have lowered in the last 10 years.