The Diffusion And Migration Of Heavy Metals In The Sediment-seawater Interface Of Jinzhou Bay And Equilibrium Distribution Behavior

Jinzhou Bay is located in the northern part of the Liaodong Bay,Bohai Sea,China.It is a small bay and surrounded by land on three sides of the bay.Jinzhou Bay is one of the most polluted bays in China.There are a large number of petrochemical plants around Jinzhou Bay,as well as zinc plants.Industrial wastes cause heavy metal pollution in rivers such as Wuli River and Cishan River in Jinzhou Bay,which makes Jinzhou Bay have a long history of heavy metal pollution.Heavy metals are non-degradable and migrate to the seabed during sedimentation,diffusion migration and burial at the sediment-seawater interface.They are released by biological,physical and chemical reactions and converted into dissolved state,but at the same time,contaminated sediments can also become the source of heavy metals in the overlying water causes secondary pollution,threatening the health of marine life and even humans.Samples were collected from the inside and outside of the bay of Jinzhou Bay in autumn,spring and summer,from September 2017 to August 2018.The dissolved and particulate heavy metals(Fe,Mn,Cu,Co,Ni,Zn,Cd and Pb)in seawater,pore water and sediment were analyzed.Analyzing the distribution characteristics of heavy metals in seawater and pore waters in different seasons and the migration,migration laws at the sediment-seawater interface in Jinzhou Bay.The study shows that the dissolved heavy metal pollution in Jinzhou Bay is higher than that outside the bay,and the summer is higher than other seasons.The content of Cd and Zn is much higher than other bays.It is the two metals with heavy pollution,and is subject to runoff,industrial waste and human waste.The impact of domestic sewage discharge is significant.The dissolved heavy metals(Co,Ni,Zn,Cd,Pb)in the pore water of Jinzhou Bay are consistent with the seasons,and the content of Cu in the pore water in summer is much higher than other seasons.The vertical distribution of dissolved heavy metals in pore water mostly shows the distribution trend of high surface layer and rapid decrease of bottom layer.Surface pore water is obviously affected by the concentration of overlying water.The comparison of the content of heavy metals in the surface sediments of Jinzhou Bay with other bays at home and abroad shows that the pollution of Cd and Zn is more serious.The benthic flux of metal in Jinzhou Bay were calculated using the PROFILE program.The results showed that the heavy metals Zn,Co,Ni and Pb in Jinzhou Bay are sediments diffused into the water,indicating that the sediment is an important source of overburden metal.The heavy metal Cu diffuses into the sediment in spring.In the autumn and summer,the sediments diffuse into the water,which is affected by the temperature.The heavy metal Cd is the water diffusing to the sediments,indicating that the water is the source of sediment heavy metals,which continuously migrates to the sediments and is seriously polluted.The SCEM model was used to analyze and compare the measured and predicted values of the free ion concentration of several metals in the upper seawater.The results show that the measured values of Cu,Zn and Pb are in good agreement with the predicted values,and the predicted values are slightly higher than the measured values,indicating that The sediment-seawater interface of Jinzhou Bay did not reach equilibrium,and the sediments continued to migrate to the seawater to migrate heavy metals,which was consistent with the research results of pore water diffusion flux,causing secondary pollution to seawater.The predicted value of Cd is higher than the measured value,and it diffuses into the sediment in the pore water,which is inconsistent with the pore water test result.It breaks through the toxicity threshold of Cd in the water,reflecting the possible anti-virus mechanism of the organism in the upper water.