Sediment Characteristics Research Of The Northern Bohai Sea

In order to investigate the regional sedimentary environment,and further to serve the development of our country economy.In August 2014,the surface sediment samples were sampled in the northern Bohai Sea.Then the particle size,mineral composition,distribution and characteristics of heavy metal were studied,and to investigate the sources of surface sediment,depositional environment and environmental quality of the Bohai Sea.Our study can help assess and warn the water environmental quality,and further provide the basis data for mariculture and marine ecological restoration.Meanwhile,this study can provide scientific basis for reasonable development of marine resources and protect marine ecological environment.The sediment grain size distribution characteristics and types were analyzed by the 23 surface heavy sediment samples of the northern Bohai Sea,and discussed the sedimentary environment and sedimentary process.The results showed that the sand content range from 5.76 to 83.76%,and the average was 29.70%;Silt content range from 12.80 to 73.79%,the average mean value was 59.16%;Clay content range from 3.45 to 20.01%,average was 11.14%.The average particle size range from 5.34 to 9.00?;Three kinds of mineral were identified by using sediment classification method of the Folk in the northern part of Bohai Sea,and the percentage of silty sand(zs),sandy silt sand(sz),respectively.The sandy silt(sz)is widely distributed,and its percentage is high,and also the main sediment types in the study area.Overall,the higher average particle size in the north Liaodong bay,and also with higher sandy component content.However,with low average surface sediment particle size in the west side of northern Bohai Sea,and the main sediment types were silt and argillaceous.The surface sediment is derived from the rivers carry sediment,the tidal current and longshore current control plays a key role in the distribution of the surface sediment.The heavy metal content was determined by using inductively coupled plasma mass spectrometry based on 23 surface sediment samples from the northern Bohai Sea area.We assessed the environmental quality,distribution characteristics and predict their risks by using conjointly cumulative index and potential risk index of heavy metals in surface sediments in the study area.Results showed that the content of main heavy metal from high to low in turn are As,Cd,Pb,Co,Cu,Cr,V,Zn and Mn.The cumulative index and potential risk index showed that Mn,Zn,V and Cr are not polluted,and Cu,Co,Pb in some sample with slightly polluted,while Cd and As with more serious pollution.The heavy metal mainly distributed in the northern of Caofeidian and estuary of Dashihe river with decline trend from the coast to the foreshore,while with low value mainly in estuary of Fuzhou river and northern of the study area.Pb,Ni and As with high value in estuary of Gou river and Fuzhou river,and Mn and As are more higher in estuary of Fuzhou river.The distribution of surface sediment is not only influenced by the particle size of the sediment but also related to development of social economy and environmental protection policies in the study area.Therefore,in order to maintain our living environment,the provinces along the coastal area should alter the unreasonable way of producing.The detrital mineral assemblages and distribution characteristics as indicators of provenance and dispersal pattern in surface sediments were analyzed by using method of spatial interpolation and cluster analysis.Results showed that the average content of the detrital mineral is 17.1%,including 9 light minerals(96.77% on average)and 33 heavy minerals(3.23% on average).The cluster method of Q type showed that the northern Bohai Sea could be divided into two mineral assemblage zones along the east-west direction,due to the bedrock differences between two tectonic blocks.Further,it can be divided into 4 mineral assemblage zones(W1,W2,E1 and E2)by laws of watershed erosion source area differences and weathering handling.The W1 and W2 in the west and southwest classified mainly by content of the pyroxene,while E1 and E2 in the northeast and southeast of the study area classified mainly by the zoisite.Assemblages and distributions pattern of detrital mineral are mainly controlled by provenances,and also affected by hydrody namic and grain density.The contribution for explaining the characteristics of mineral composition with provenance and submarine topography factor accounted for 41.91% and 22.74%,respectively.