Heavy Metal Accumulation And Pollution Evaluation In Wanggang Tidal Flat

Northern coastal areas of Jiangsu are one of the regions with higher levels of economic and social development in C hina.With the improvement of industrialization and urbanization,high-intensity human activities have broken the ecological balance and brought various hidden dangers to the sensitive and fragile tidal flat environment.The problem of heavy metal pollution is one of the environmental issues that are of most concern to the world.As the"sink"of heavy metals,the tidal sediment receives the heavy metals from various channels first,and excessive human input will cause heavy metal pollution.This paper selects Wanggang tidal flat in Dafeng district,Yancheng city,Jiangsu province as the research area.In this paper,laboratory chemical analysis is performed on the collected surface and columnar sediments,and a variety of scientific research methods such as particle size parameter analysis,deposition rate estimation model,multivariate statistical analysis,and quantitative assessment of heavy metal pollution are integrated.This paper analyzes the spatial and temporal distribution characteristics of the sedimentary environment and the heavy metal content in the tidal bank of Wanggang,preliminarily traces the source of heavy metals,determines the pollution degree and potential ecological risks of heavy metals,reveals the response relationship between heavy metal deposition records and human activities,and assits the prevention and treatment of heavy metal pollution in tidal flats to make scientific decisions.The results are as follows:?1?The heavy metal elements Zn,Pb,Cr,Cu,Mn,and Fe in the surface sediments showed different degrees of heavy metal enrichment and large spatial distribution differences in the Wanggang tidal flat.The EF of heavy metal elements Zn,Pb and Cr in high and medium tidal flat is 0?1,which belongs to moderate anthropogenic enrichment,and the EF of C u at the high tide beach is 2?5,which belongs to moderate artificial enrichment;The I_geo of Cu and Pb in high tide and middle tide is 0?1,which is light pollution;The RI in Wanggang tidal flat is less than 140,which is low risk.In general,except for Mn and Fe,Zn,Pb,Cr and Cu are all pollutive heavy metal elements in the tidal flat of Wanggang.?2?The Wanggang tidal flat is a silt-sandy coast,with a strong hydrodynamic force,coarse sediment particles,and a complex hydrodynamic or provenance environment.The deposition rate of the tidal flat in Wanggang at 4.12cm/a.The vertical distribution of heavy metals in the columnar samples is related to the silty clay content,storm surge and human activities in the particle size components.Combined with the enrichment coefficient and ground accumulation index of columnar samples,it is found that Pb and C u had slightly polluted the tidewater environment of Wanggang mainly during the periods of 1990-1995 and 2001-2005,which indicated that the artificial input of heavy metals increased.The columnar samples throughout the sedimentary age are low-risk states,indicating that the historical ecological environment of Wanggang tidal flat is good.The RI values are increasing year by year,which indicates that the ecological environment of low and middle tide beaches needs special attention in the future.?3?Zn,Pb,and Cu are mainly affected by man-made sources;Mn and Fe are mainly affected by the parent material of the waste Yellow River and the Yangtze River;Cr is controlled by both human and natural sources.The change process of human activities in the Wanggang tidal flat is as follows:from 1990 to 1995,the coastal areas of Jiangsu province were in the period of rapid industrialization,and the environmental protection concept was weak,which led to the massive enrichment of Pb and C u.From 1995 to 2002,the establishment of Dafeng Elk national nature reserve slowed down the process of industrialization,and the enrichment of Pb and Cu was alleviated.After 2003,the establishment of Dafeng port economic development zone promoted industrial upgrading again,and the awareness of environmental protection was strengthened.Pb and C u were enriched again,but the pollution situation was not aggravated.