Pollution And Sources Of Heavy Metals In Sediments Offshore Area Of Yangtze River Estuary Based On The Total Content And Speciation Analysis

At present,heavy metals in the environment mainly come from human activities after the Industrial Revolution.Most of the heavy metal pollutants in the environment enter the ocean through surface runoff and atmospheric sedimentation.The ocean provides humans with production and living resources,and also carries heavy metals from the land.Pollutants.As a typical cumulative pollutant,heavy metals have significant biotoxicity and persistence,posing a potential threat to the marine ecological environment.Because heavy metals are bioaccumulative,they ultimately affect human health through the enrichment of the food chain.The Yangtze River estuary is the largest estuary in China.At the same time,the Yangtze River Delta Economic Circle is one of the most economically developed regions in China.With the population growth and economic development of the Yangtze River Basin,water pollution in the Yangtze River estuary and nearby waters has attracted much attention.Located in Zhoushan City,Zhejiang Province,south of the Yangtze River Estuary,it is a national marine special protection area.The sea area is rich in marine biological resources,unique island reef landforms,and intertidal wetland ecosystems.Based on the data of seven heavy metals(Cr?As?Ni?Zn?Pb?Cu?Cd)in the surface sediments of the Offshore area of Yangtze River Estuary,the distribution characteristics and geochemistry of the heavy metals in the surface and vertical sediments in the Ma'an archipelago,Zhoushan,Zhejiang Province were studied.Indicator pH value?Redox potential(Eh)?Granularity(D[3,2])and other control factors,combined with the enrichment factor coefficient(EF)The pollution characteristics and sources of heavy metals in the sediments of the Offshore area of Yangtze River Estuary and the Ma'an archipelago were explored.By comparing and studying the distribution characteristics of heavy metals in the sediments of the sea area,the morphology and potential ecological risks of heavy metals in the sediments of the sea area can be analyzed systematically.It provides scientific basis for the restoration of the ecological environment of the sea area and the development and utilization of marine resources.The research has reached the following conclusions:(1)The distribution of heavy metals in the surface sediments of the study area is remarkable.The sediments in the surface waters off the Offshore area of Yangtze River Estuary are neutral-weakly acidic and belong to an oxidizing environment.The surface sediments of the Ma'an archipelago are neutral-weakly alkaline and belong to a reducing environment.The pH value shows far coast>near coast.From the horizontal distribution,the grain size composition(D[3,2])of the surface sediments of the Ma'an archipelago is mainly composed of gravel and clay,while the far island reef is mainly composed of gravel and gravel.From the longitudinal distribution.The grain size composition(D[3,2])of columnar sediments in the Ma'an archipelago is mainly composed of fine sand.(2)The total amount of seven heavy metals Cr?As?Ni?Zn?Pb?Cu?Cd in the sediments off the Yangtze River estuary Sediment Quality Class I Standard.In general,the average order of the heavy metal content in the Offshore area of Yangtze River Estuary and the Ma'an archipelago is:Zn>Cr>Ni>Pb>Cu>As>Cd,which is high offshore and low,and near island reefs are higher than far island reef(3)The heavy metals Cd?Cu?Zn?Pb in the surface sediments off the Offshore area of Yangtze River Estuary are mainly formed in the secondary phase,and Cr?As?Ni are the primary forms in the primary phase.The morphological characteristics of heavy metals in the surface sediments of the Ma'an Islands and the Offshore area of Yangtze River Estuary are consistent.In the heavy metals of the Ma'an archipelago,Cd is in the exchangeable and carbonate-bound state(F1)and the organic and sulfide-bound state(F3)The main occurrence forms are Zn?Pb?Cu with Fe-Mn oxide bound state(F2)as the main occurrence form,and Cr?As?Ni with residual state as the main occurrence form.The content of heavy metals in the columnar sediments of the Ma'an archipelago generally fluctuates with depth,reaching extreme values at 0.5m and 2.0m.The heavy metals Cd are mainly secondary phases,exchangeable and carbonate-bound(F1)?The Fe/Mn oxide bound state(F2)and organic and sulfide bound states(F3)are basically equivalent in the three forms.The remaining six heavy metals are mainly in the form of residues,and the effective states of seven heavy metals change vertically.Trends are cyclical and consistent.(4)Through the analysis of space pollution,it is found that the enrichment order of heavy metals in the sediments off the Offshore area of Yangtze River Estuary:Cd>Cu>Ni>Pb>Zn>Cr>As,and Cu?Cd?Zn and Pb are affected by terrestrial or human activities.Cd?Cu has a significant enrichment pollution phenomenon,Zn?Pb anthropogenic sources have not yet reached the enrichment pollution level,and Cr?As?Ni is consistent with the Ma'an archipelago mainly due to the result of natural deposition.The order of enrichment of seven heavy metals in the sediments of the Ma'an Islands sea area is:Cd>Cu>Ni>Zn>Pb>Cr>As.Comprehensive analysis of the space pollution status of the columnar sediments on the surface of the Ma'an archipelago shows that Cu?Cd has been There is a phenomenon of enrichment and pollution in the near-island reefs,where other heavy metals are mainly from natural sources.In general,the ecological risk of Cd?Cu in the Offshore area of Yangtze River Estuary is the highest,and it has great toxicity to aquatic life.It should be paid attention to.The pollution level of heavy metals in the sediments of the National Special Marine Reserve in Ma'an archipelago is relatively low.The quality repair effect is better.