Abstract:
Tessier sequential extraction procedure was used to analyze the distributions of six kinds of heavy metals in the ballast tank sediments from 10 ships.The ecological risks of the heavy metals were evaluated according to the potential ecological risk index and the ratio of secondary and primary phases.Results show that the average concentration of Zn and Cd are 3915.73×10
-6 and 6.17×10
-6, which present as the highest and the lowest contents in all of ballast sediments, respectively.In this study, Ni, Pb and Cr are found mainly distributed in the residual form, while Cd mainly exists in the organic and residual fraction.Cu is primarily belonged to the organic form and Zn mainly bounds to the Fe/Mn oxides.Hakanson ecological risk index indicates that the ecological risk of heavy metals is in the order of Cd > Zn > Cu > Pb > Ni > Cr.The risk evaluation of heavy metal based on speciation shows that the pollution of Cr, Ni and Pb in the sediments was light, while the Cd and Zn were at the level of heavy pollution.In conclusion, the heavy metals in ballast tank sediments have high potential bio-toxicity and reasonable managements and treatments are required to prevent the marine environment pollution.