Microplastics And Heavy Metal Pollution In The Intertidal Zone Of Bohai Bay And Its Ecological Risks

The intertidal zone in the Bohai Bay coastal area serves as a transitional zone between oceans and land.The vast majority of human crustaceans are derived from this source.The intertidal zone is very vulnerable to the destruction of sewage,such as human activities,soil erosion,and tidal hydrodynamic conditions.If the area is contaminated,living organisms in it will be contaminated,and humans will eat fish and shrimp that live there.Afterwards,it will directly affect the health of the body.Therefore,the environmental conditions in the intertidal zone should receive everyone's attention.Microplastics,due to various additives in its own manufacturing process,slowly degrade in the natural environment with environmental effects(such as weathering,etc.),continuously releasing toxic monomers and additives,and simultaneously adsorbing some persistent toxic substances such as heavy metals on the surface of microplastics.Hg,Pb,and other chemical substances are released into the surrounding environment,causing environmental pollution.At the same time,these microplastics are characterized by small particles,large quantities,and wide distribution.It is precisely because of this feature that microplastics are easily eaten by marine animals.As a result,animal esophageal punctures and pseudosatisfied feelings may occur.Malnutrition and other hazards pose ecological risks in the marine environment.Heavy metals are toxic and due to their inability to be degraded by the digestion of microorganisms,have a very serious impact on the intertidal zone sediments,and under certain conditions combined with organic matter will be converted into more toxic compounds.At the same time,due to periodic hydrodynamic conditions such as tidal movements and activities of various aquatic organisms,the intertidal zone will lead to the redistribution of heavy metals under various actions and will be released into the environment to produce heavy metal pollution again,which will directly harm the sea and Nearshore environment.This study collected sand samples from the intertidal zone(low tide zone,middle tide zone and high tide zone)and the upper tidal zone in Bohai Bay,and studied the types,sources,morphology and adsorbed substances in the inter-tidal Sandy zone samples.At the same time,the content of heavy metals was evaluated,and the sources and ecological risks of organic matter were analyzed and discussed by means of carbon and nitrogen stable congeners,which provided scientific reference for theresearch and supervision of intertidal pollution in Bohai Bay.The main results are as follows:(1)Experimental separation The extraction of microplastics is mainly based on the principle of density,but at this stage there is still not a completely mature set of methods.It is still in the exploratory phase.Extraction and separation of microplastics in the experiment is based on simple operation,high recovery and affordable recycling.It is considered that flotation and separation of microplastics from sediments in the intertidal zone of Bohai Bay can be performed by direct flotation of saturated NaCl solution on open aluminum plates.(2)Three kinds of microplastics such as fibers,foams and films were observed in the sand samples of the intertidal intertidal zone in the Bohai Bay.The fiber-based microplastics were the main types,which were influenced by the geological conditions and hydrodynamic forces in the intertidal zone.And human activities and other factors.(3)The surface of micro-plastics in the tidal intertidal zone of Bohai Bay is rough,torn,bulging,and exists in this porous structure,which is affected by aging,weathering,and erosion.Adsorption of pollutants on the surface of micro-plastics,Fe,Mg,and Al are the main metal elements in fiber-based micro-plastics,and Fe,Mg,Al,Ca,and Na in the main adsorbents of films and foamed micro-plastics.Mixed with clay minerals and other impurities.(4)The contents of heavy metals such as Hg,Pb,and Cd in the sandy intertidal sand sediments in the Bohai Bay coastal area were determined.The content of heavy metals Hg was more than twice that of sediments in Bohai Bay,and the content of heavy metal Cd was far.Above the background value of sediments,the Pb content is lower than the background value,which is pollution-free.(5)According to the Igeo analysis results,it can be seen that the Hg pollution level is 1,which means no pollution to moderate pollution;Cd pollution level is 4,indicating strong pollution;Pb pollution level is 0,That means no pollution.According to the analysis results of the enrichment coefficient method(EF),heavy metal Hg is moderately to highly enriched,heavy metal Cd belongs to ultra-high enrichment,and heavy metal Pb is not enriched.The heavy metals Hg and Cd are enriched by human activities.Comprehensive Hg pollution is light pollution,Cd is high pollution,and Pb is pollution-free.(6)The biological impact value of heavy metal Cd is between ERL and ERM,indicating that occasionally it will cause negative biological effects;the biological impact value of heavy metal Hg is slightly lower than that of ERL,indicating that heavy metal Hg is at the margin of little biological negative effect.Given a certain amount of attention,if it continues to accumulate,it will cause biological negative effects;the content of heavy metal Pb is much lower than that of ERL,indicating that it will rarely cause biological negative effects.(7)The LOI,TOC and TN in sandy sediments were analyzed in this study.The results showed that the organic index ranged from 0.058%to 0.12%,and the pollution level was class ?,which was a relatively clean type.The average value of TN(%)is 0.010%,then the pollution level of organic nitrogen is Grade ?,which belongs to the clean type.(8)This study also analyzed the stable isotope compositions(?13C and ?15N)of carbon and nitrogen in sandy sediments.The results showed that the range of ?13C changes was-21.17 ‰ to-19.57 ‰,with an average of-20.23 ‰.The 815N variation ranged from 4.09‰ to 5.28‰,with an average of 4.16‰.According to the values of?13C and ?15N,the possible sources Gan be analyzed.The results show that the possible sources of organic matter in the intertidal sands of the Bohai Bay are relatively complex,mainly the natural terrestrial input and its own aquatic organisms,mainly terrestrial C4 plants.A comprehensive source of organic matter and marine plankton.(9)Integrate the values of ?13C,?15N,and TOC/TN,and use the carbon and nitrogen stable isotope composition to determine the possible sources of TOC and other pollutants.The results show that the source of organic matter in the intertidal zone of the Bohai Bay is diverse and is mainly terrestrial.C4 plants,soil organic matter,and marine aquatic plants,and TOC/TN cannot be particularly stringent in determining the source of organic matter.At the same time,the correlation analysis of TOC,TN and LOI with heavy metals Hg,Cd and Pb showed that TOC and TN do not have similar sources with Hg,Cd and Pb.