The Status Of Heavy Metal Pollution In Jinzhou Bay And Its Effect On DNA Damage In Clam (Ruditapes Philippinarum)

Jinzhou Bay has been identified as one of the main heavy metal polluted coastal regions along the Chinese coastline.By monitoring of heavy metal in the water, sediment and organism of Jinzhou Bay,the trend of heavy metal distribution and change was carried on,and genotoxic damage was tested in gill cells of clam(Ruditapes philippinarum) exposed to heavy metal in vitro using the single cell gel electrophoresis (Comet assay).The main results are shown as follows:(1) The highest concentrations of dissolved metal were determined in samples collected from southwest of the bay near sewage outfalls and plants.The concentrations of dissolved metals increased toward inshore as compared with the offshore.The principal contaminated factors were Zn and Cd,and next was Pb in the Jinzhou Bay. The pollution level from high to low is Cd＞Zn＞Pb＞Cu.Jinzhou Bay areas is most contaminative areas.(2) The distribution trend of heavy metal in sediment of Xiaoling Estuary is increasing from inshore to offshore,that of Lianshan Bay is contrary.The distribution of Cu and Pb in Jinzhou Bay is irregular,but that of Zn increase with the distance from pollution source,and that of Cd is contrary.The distribution trend of heavy metal in tidal sediment of Jinzhou Bay is increasing from inshore to sea.Potential ecological risk order is following:Cd＞Cu＞Pb＞Zn in sea area sediment and Cd＞Pb＞Cu＞Zn in tidal sediment.Potential ecological risk index in sea area and tidal sediment is 77.83 and 445.84,respectively.The degree of contamination and the potential ecological risk are low in sea area sediment and extremely higher in tidal sediment,which Cd is the main contribute to.The degree of contamination and the potential ecological risk order is following:Jinzhou Bay＞Xiaoling Estuary＞Lianshan Bay.(3) Cu,Cd,As and Hg content in marine benthons mollusk is below the classⅠstandard for marine biological quality,but Pb and Zn exceed the classⅠstandard. The degree of contamination in marine mollusk order is following:Pb＞Zn＞As＞Cd＞Cu＞Hg.The sediment enrich more heavy metal than mollusk.The accumulate capability sequence of sediment is Pb＞Cu＞Zn＞Cd,that of marine mollusk is Cu＞ Pb＞Zn＞Cd.(4) There is good dose-effect relationship for DNA damage induced by Cu,Pb and Cd. Zn treatment has no influence on DNA damage levels of gill cells isolated from clam(R. philippinarum) in vitro.As expected,gill cells exhibit a increase in DNA damage induced by Cd at very low concentrations(the ClassⅠof Sea Water Quality Standard in China),a significant increase in DNA damage induced by Cd,Cu and Pb from the ClassⅡ.DNA damage of gill cells is not detected at the classⅠof 4 heavy metals blended concentration,the classⅡof 4 heavy metals blended concentration exposures caused significant differences in DNA damage of gill cells.DNA damage levels of gill cells shows a decreasing trend with the ClassⅢandⅣconcentration.DNA damage levels induced by the mean 4 heavy metals blended concentration of Jinzhou Bay between that of induced by the ClassⅢandⅣblended concentration.The comet assay could represent a useful test to evaluate the biological consequences of environmental contamination by metals on marine organisms,being sensitive to cellular damage...