Study Of Distribution Of Sediment Heavy Metals In Bohai Bay And Its Effect Factors

Study on the distribution of sediment heavy metals in Bohai Bay and its effect factors is helpful to understand the regularity and mechanism of human activities on environmental change,and to provide scientific and technological support for ecological environment protection and restoration.Sediment samples at eighteen stations in the Bohai Bay were collected during October-November 2012 and then analyzed in the laboratory,including four core samples of the sediments.Combined with the previous research results,the results show that the distributions of the five major heavy metals（Cr,Cu,Zn,Cd,Pb）are similar,and there are three regions with high concentration of heavy metals,one is located in the northwest and the other two are located in the centre and the mouth of the Bohai Bay.Grain size of four core samples were analyzed and the results showed that the average particle size of sediment samples range of 2.5-3?,the overall particles are fine and flow is weak.Based on the geological accumulation index,the pollution levels of Cu,Zn,Pb were not contaminated,and Cr,Cd were evaluated as lightly polluted.The correlation analysis and principal component analysis were used to analyze the sources of pollutants.The results indicate that the regions with high concentration of heavy metals may be associated with the discharge of sewage outlet.The hydrodynamic model for simulating the tidal residual current in Bohai Bay,the results show that the regions with high concentration of heavy metals are located in the vortex areas of the residual current,and the hydrodynamic forces in the three areas with high concentration were weaker,which indicate that the hydrodynamic factors were the main reason for the high concentration areas of heavy metals.The distribution characteristics of sediment particle size were analyzed to explore the relation between the distribution characteristics of heavy metals and depositional environments.The vertical distribution of radionuclide ²¹⁰Pb activity was further analysed.The activities of ²¹⁰Pb decays regularly with buried depth in the northwest and the center of the Bohai Bay,which indicates that the sedimentary condition is relatively stable and favorable for the deposition of sediments and its associated heavy metals.The results of hydrodynamic simulation and radioactive isotopes analysis are consistent on the whole,which proves that the hydrodynamic condition is the main reason for the formation of high concentration of heavy metals in sediments in the northwest and central and the bay mouth sediments of Bohai Bay.