Dissolved Cu, Pb, Zn and Cd in the South China Sea surface waters

A total of 106 surface water samples was collected in the South China Sea during two transects in June and December 1998.The samples were collected with strictly contamination free procedure and trace metals were mea sured by clean laboratory methods and GFAAS.The mean concentrations for the dissolved fractions are Cu 0.100μg/dm³,Pb 0.060μg/dm³,Zn 0.086μg/dm³,Cd 0.007μg/dm³,which is close to the world open oceans level. The spatial distribution of trace heavy metals shows higher concentrations in offshore area and lower concentrations in the central South China Sea,and the concentrations decrease with the distance from the offshore,which sugg ests the existence of significant continental shelf input of trace heavy metals.The correlationship among the elements is better in summer than that in winter.Cu is positively co rrelated with Cd in the two seasons and it is also found for the first time that they are positively correlated with nutrients in the South China Sea surface waters,which further indicate the biogeochemical cycle of these elements in the marine environment.The baseline value of Cu,Pb,Zn,Cd in the South China Sea surface waters is obtained through statistical analysis.