A study on seawater apparent heavy metalcomplexation capacity in the Haikou Bay

Using semidifferential stripping technique combined with pre-equilibrium complexometric titration, the abnormal phenomena appeared in determining apparent complexation capacity (ACC) are discussed and the improved method for determining ACC is presented in the article.The accuracy of ACC measurement results is tested theoretitelly and experimentally.Based on determination of ACC_Cu, ACC_Pb and ACC_Cd, copper was selected for complexometric titration to determine ACC and the results are proved to be reasonable.ACC_Cu measured in the Haikou Bay surface water is in the range of 166.4-320.2 nmol/dm³, with the mean value of 240.9 nmol/dm³, the maximum value aramd domestic drainage outfall, and the values in other stations are comparatively homogenous.The condition formation constant is in the range of 3.46×10⁷-4.76×10⁸, and the mean value is 1.7×10⁸.Based on the 1:1 comlexing model of copper-natural organic ligand and the toxic concentration limit to marine organisms, seawater self-purification capacity in the Haikou Bay is calculated to be 7.43 μg/dm³.