Sediments Distribution And Heavy Metal Pollution Assessment In The Jiaozhou Bay

The Jiaozhou Bay area has been a major coastal town long time in China relying on the marine resources and shipping.At the same time of economic prosperity,land-based sewage discharge,marine sewage discharge,and unreasonable aquatic product development have also brought environmental contaminations,such as the shore erosion,the local desertification,the water eutrophication,and the organic pollution.The heavy metal pollution has attracted widespread attention due to it's difficult to biodegrade,toxic and enriched with the food chain.We discussed the sedimentary environment,the distribution characteristics of sediment particle size parameters and main sediment types in Jiaozhou Bay used the surface and columnar sediments?44 surface samples and 4 column samples?.The distribution of heavy metals in sediments from different locations and depths was analyzed by the contents of seven major heavy metals such as Cu,Pb,Zn,Cr,Cd,Hg and As in columnar sediments.The degree of heavy metal contamination was evaluated using the geoaccumulation index and Hakanson's method.Studying the sediment distribution pattern and heavy metal pollution is of great significance to the rational development of Jiaozhou Bay areas and to environmental protection.Moreover,this work provides the foundation and basis for other bays environmental planning and sustainable development.The main conclusions were as follows:1.The average particle size of surface sediments in Jiaozhou Bay varies widely?1.15⁷.10??,with an average of 5.68?.The sediment particle size fraction is dominated by silt?58.59%?,the average content of sand and clay is 23.59%and 17.27%.The sediments in northwest Jiaozhou Bay are dominated by clayey silt or silt,those in the central region were dominated by sandy silt,and those in the northeast are dominated by silt.2.From northwest to mouth of Jiaozhou bay,the surface sediments were coarse-fine-coarse banded.The coarse particles were concentrated in the Dagu River estuary and the mouth,and the fine particles were relatively well distributed in the bay top.The particle size distribution frequency curve of the sediment shows that the kurtosis is mainly of the medium distribution type,and the sediments with negative deviation are concentrated in the outer margin of the Dagu river estuary delta.3.There are four different types of sedimentary environments in Jiaozhou Bay.?I?The top of the bay and the shallow waters near the shore;?II?The Dagu-Yang river underwater delta.?III?The southwest and central of the bay.?IV?A narrow area around the Cangkou sand ridge to the bay mouth.4.The heavy metal concentrations are high in the east and low in the middle of the bay,and an increasing trend can be observed from the center of the bay to the periphery.The heavy metal concentration in the east is consistently high,but in other regions,the concentration increases towards the surface layer and exhibits incremental changes that are consistent with various social and economic development stages.The overall pollution level in northern Jiaozhou Bay is relatively low.5.The I_geo and_rEⁱ values indicate that Hg contamination has occurred throughout the study area and that some areas are polluted with Cu and Cd.The concentration of heavy metals in sediments is generally higher than that in shallow sediments from the Yellow Sea.The potential ecological risks associated with the sediments include a moderate to high ecological risk for Hg,moderate ecological risk for Cd,and low ecological risk for all other heavy metals.The results of this investigation indicate the need for further research into the sources of heavy metals.