Preliminary Study On The Transfering Characteristics Of Microplastics Along Marine Food Chain And Investigation On Its Secondary Sources

In 2015,the United Nations Environment Conference listed marine plastic waste and marine microplastics as the second most important environmental problem in the world.The problem of microplastic pollution has become an environmental issue that is widely concerned in the current academic community.Microplastics are difficult to degrade,exist in the environment for a long time.They are easy to adhere to and accumulate persistent organic pollutants,and are easily adsorbed by shellfish or eaten by fish.In addition,microplastics in the water can be directly or indirectly ingested along the food chain,posing a potential risk to human health.Its sources include primary and secondary sources.Primary sources are microplastic particles that are directly discharged into the environment,such as abrasives in toothpaste and foaming agents in skin care products;secondary sources are formed by the degradation of large plastics that are discharged into the environment.At present,there is no uniform method for the separation of microplastics in organisms,and the understanding of the transfer and accumulation characteristics of microplastics in vivo is still limited.Therefore,the establishment of microplastic separation methods in vivo and the study of microplastic contamination in organisms have important practical significance.In addition,investigating the source of microplastics and effectively controlling them from the source is beneficial to reducing the generation of microplastics from the source and curbing the environmental risks.Based on the above reasons,this study firstly explored an effective,harmless and universal method for separating microplastics in organisms by using biological snails as an example.The distribution characteristics of microplastics in Taihu snails are determined by this method.And the stability of the method was also verified.Secondly,the microplastics abundance of wild shellfish and fish in Liaodong Bay was determined by this method.The distribution characteristics of microplastics in shellfish and fish were studied to explore the transfer of microplastics in different organisms.Finally,taking the plastic waste discharge characteristics of key coastal industries in the typical area of Wenzhou as an example,further preliminary investigation on the secondary source of marine microplastics was carried out.To expose the characteristics of marine microplastic pollution sources from the perspective of industry and provide a scientific basis for the management of marine plastic waste,the survey was conducted.The specific work content and research results of this thesis are as follows:1)Tris-HCl lysate,proteinase K,and 10%KOH solution were used to digest the biological tissue of snails(B.aeruginosa).Compared with several methods used commonly,the method was found to be efficient,mild,and time-saving.Using this method,only the polymethyl terephthalate particles were slightly dissolved,and polyethylene,polypropylene,and polyvinyl chloride microplastics particles did not change significantly after treatment.The recovery rate of the method is 73~89%;2)The microplastics in the Taihu snail(B.aeruginosa)were measured.The results showed that the abundance of microplastics in the Taihu snail was 2.30~9.33particles/individual(or 2.12~8.49 particles/g wet weight),70%of microplastic particle size ranged from 100 to 400?m,mainly based on micro-fiber.The microplastics obtained by micro-infrared identification are made of polyvinyl acetate,polyethylene terephthalate,polystyrene,and polyamide;3)The microplastic abundance of six kinds of shellfish(include Mactra veneriformis Reeve,Sinonovacula constricta(Lamarck),Ruditapes philippinarum(Adams et Reeve),Cyclina sinensis(Gmelin),Mactra chinensis Philippi,and Rapana venosa(Valenciennes))in Liaodong bay was determined.And the average abundance of microplastics is 10.9±6.74 particles/individual or 5.9±4.93 particles/g wet weight in shellfish.Most microplastics in size range from 60 to 500?m.And the indentification materials of microplastics include polyethylene terephthalate,polystyrene,poly(N-methacrylamide),polyurethane,polymer paraffin mixture,and polyvinyl acetamide;4)The microplastic abundance of six species of fish(include Pseudosciaena polyactis Bleeker,Trichiurus haumela(Forskal),Nibea albiflora(Richardson),Synechogobius ommeturus(Richardson),Lateolabrax maculatus McClelland,and Liza haematochelia(Temminck et Schlegel))in Liaodong bay was determined.The average microplastics abundance is 12.16±11.36 particles/individual or 7.48±3.41 particles/g wet weight in fish.Compared with the gill,the microplastics in fish's gastrointestinal are more abundant.The microplastics are made of polyamide,nylon,polyethylene glycol methacrylate,polyurethane,polyvinyl chloride,polyethylene,polyester copolyamide,polyethylene tetradecylene,polyethylene copolymer,polypropylene copolymer,and polystyrene.Moreover,after calculation of the trophic magnifcation factor TMF,the TMF between shellfish and fish was 1.27.And the TMF value was greater than 1,indicating that the microplastic abundance had obvious biomagnification effect from shell to fish.5)Taking the typical coastal area of Wenzhou as an example,the composition of offshore plastic waste was analyzed through on-site sampling survey.Then the preliminary investigation of plastic waste discharge characteristics in Wenzhou coastal industry was carried out and the annual emissions of the industry were estimated.And the results as follows,the average density of plastic waste in Wenzhou coastal area was is 2.72 g/m~2,the main plastic waste component is plastic bag;the material types of plastic waste in different industrial areas in Wenzhou mainly include polyethylene,high-density polyethylene,polystyrene,and polypropylene;the annual amount of plastic waste discharged from the marine fishery activity area is the highest,about 1.09×10~4t/year.