Distribution Characteristics And Pollution Evaluation Of Heavy Metals In Surface Sediments In The Coastal Waters Of Central Jiangsu

Jiangsu coast is in the process of high-speed industrialization,urbanization and coastal zone development.At the same time,coastal ports are experiencing high-speed construction and development,and tidal flats,ports,fisheries and other marine resources are exploited and utilized on a large scale,which leads to the disturbance and destruction of marine ecosystems in coastal areas.The coastal areas in central Jiangsu province are distributed with national-level wetland rare birds protection areas,which are coastal wetlands with great ecological value.the discharge of pollutants into the sea and the exploitation of marine resources have had a great impact on the environmental quality and ecosystem health of coastal wetlands,resulting in the degradation of wetland ecosystems and the damage of ecological functions.Pollutants carrying a large number of heavy metals are discharged into the sea,and heavy metals have significant biological toxicity and are difficult to be biodegraded.Heavy metals are absorbed by suspended substances in water,settled to the bottom,and enriched in the bottom sediments,which eventually destroyed marine resources and marine ecological environment to varying degrees.With the rapid development of industry and agriculture,heavy metal pollution has become an important factor threatening the health of regional ecosystems,and attracted extensive attention from academia.It has become a common research hotspot of geographic science,environmental science and marine science,and an important indicator of regional environmental quality assessment.In this paper,the coastal waters in central Jiangsu province are taken as the research scope,and SPSS and ArcGIS software are used to analyze and process the heavy metal content data of the surface sediment investigation station in November 2016 in Sheyang estuary waters,the surface sediment investigation station in November 2012 in Dafeng harbor waters and the surface sediment investigation station in November 2015 in east xiaoyangkou waters,so as to explore the spatial distribution and sources of heavy metal elements.From an unascertained mathematical point of view,the geological accumulation index model based on blind number theory was used to evaluate the pollution of heavy metals,which provided reliable theoretical basis for the control and monitoring of heavy metal pollution in coastal waters of central Jiangsu,and provided reference for the planning,protection and restoration of ecological environment in the waters.The main results of this study are as follows:(1)The average contents of heavy metal elements As,Hg,Cu,Pb,Zn,Cr,and Cd in surface sediments of Sheyang Estuary are respectively 9.61,0.0136,22,23.5,68.5,44.1,and 0.177 mg/kg.The average contents of heavy metal elements As,Hg,Cu,Pb,Zn,Cr,and Cd in the surface sediments of the Dafenggang Sea were 5.61,0.0142,16.90,17.59,65.95,40.32,and 0.122 mg/kg,respectively,such as surface sediments in the Rudong Xiaoyakou waters.The average contents of heavy metal elements As,Hg,Cu,Pb,Zn,Cr,and Cd were 7.72,0.0133,15.52,16.42,64.38,40.47,and 0.0925 mg/kg,respectively,which all met the "quality of marine sediments of the People's Republic of China".(GB 18668-2002)specifies a type of standard.The average concentrations of As,Cu,Pb,Zn,and Cd in the Sheyang estuary and Rudong Xiaoyangkou are higher than those in sediments in the Jiangsu Sea.Cu,Pb,Zn,and Cd in the Dafenggang Sea area The average content of heavy metals was higher than that of heavy metals in sediments of Jiangsu Province.(2)The results of the spatial distribution of heavy metals show that the contents of As,Hg and Cu in the estuary of Sheyang estuary increase from the nearshore to the offshore;the contents of Pb and Zn increase from the northwest to the southeast;Cr Except Sheyang estuary nearshore,the contents of other areas are all high;the Cd element increases from north to south.The distribution of As and Cd in the Dafenggang Sea area tends to be low in the middle and high in the sides;Hg,Pb,and Zn have a banded high value outside the Wanggang estuary;the high values of Cu and Cr are distributed in the Near the mouth of the Zhugang River.The As and Pb elements in Rudong Xiaoyangkou waters are increasing from east to west;Hg elements are high in the coastal high beach and along the Tuyuang-Huangshayang waterway to the lower sea,both sides of the Jiangjiasha and the salmon sand The contents of Cu,Cr,and Cd are high in the east and south of the study area;the high value of Zn is distributed in the Longyuan wind farm offshore of the digging area.(3)The results of heavy metal element source study showed that the similarity of As and Hg elements in the Sheyang estuary sea area is relatively high,which originates from the outlying sea area and may be related to the history of agricultural non-point source pollution;similarity of Hg,Pb,and Zn elements in the Dafenggang sea area.The higher levels may come from the direct effluent and shipping vessels near the estuary of the Wanggang River.The Cu and Cd elements in the Rudong Xiaoyangkou waters are relatively similar and may be related to industrial and agricultural wastewater pollution on the east and south sides of the study area.(4)The results of geological accumulation index evaluation model based on blind number theory show that As,Hg,Cu,Zn,and Cr in surface sediments of Sheyang estuary are all clean grade;Pb elements are light pollution grade;Cd is Medium pollution level.The As,Hg,Cu,Pb,Zn,and Cr elements in the Dafenggang Sea and Rudong Xiaoyangkou waters are clean grades,and the Cd elements are lightly polluted.The result of the definitive evaluation of the geological accumulation index shows that,except for the light pollution level of Pb in the Dafenggang sea area,it is the same as the above evaluation level.