The distribution and speciation of dissolved Cd and Pb in the Bohai Sea and Yellow Sea, China

The speciation of dissolved trace metals is important due to its closely linkage with toxicity and bioavailability in seawater. We investigate the speciation of dissolved Pb (DPb) and Cd (DCd), and their spatial distributions in the Yellow Sea and Bohai Sea, China. The results showed that the organic complexation of DPb and DCd accounted for 35 +/- 14 % and 75 +/- 10 % of their dissolved concentrations, respectively. The measured free ion activity of Cd ({Cd2 +}) and organic ligand concentration of Cd ([LCd]) were highest near the Yellow River mouth, where the free ion activity of Pb ({Pb2+}) were also found to be the highest. In this study, both {Pb2+} and {Cd2+} did not exceed the toxicity threshold, and they were identified not toxic in the waters of the Yellow Sea and Bohai Seas, but biological accumulation effects potentially exist.