Study On The Occurrence Characteristics Of Microplastics In Benthic Fauna Of Typical Area Of Poyang Lake

Microplastics refer to plastic particles with a particle size of less than 5mm.As a new type of pollutant,microplastics have received widespread attention around the world.Microplastics have the characteristics of persistence,universality,and hydrophobicity.They can absorb organic pollutants and can pass Ocean currents affect the global distribution of pollutants due to migration and diffusion.The pollution of microplastics directly threatens ecology,food safety and even human health.This study selects three typical areas of Poyang Lake:the five rivers estuary(Ganjiang,Raohe,Xinjiang,Fuhe,Xiushui),nature reserves and the estuary of Poyang Lake.Dominant benthic animals such as the sediment,Bellamya aeruginosa,Unio douglasiae,ect are the research objects.Through the methods of tissue digestion,density separation,stereomicroscopy and spectral identification,the microplastic pollution in the benthic animals in the typical area of Poyang Lake has been clarified.The ecological risk assessment of microplastics in the environment provides basic data.The average abundance of microplastics in the sediments of the Five Rivers inlet was 1261 n·kg^-1.The results of microplastic contamination surveys in benthic animals showed that the average abundance of Bellamya aeruginosa ranged from 1.48 to 2.48items/g,with different degrees of microplastic contamination in benthic animals such as Cipangopaludina chinensis and Unio douglasiae.The benthic fauna contained many different types of microplastics,including pellets,fragments,films and fibers.The microplastics in different regions and different benthic animals have similar characteristics in type and size.They are mainly fiber-based microplastics,and the most common particle size is<1mm.After identification,the polymer types include polyethylene(PE),polypropylene(PP),polystyrene(PS),etc.In order to analyze the distribution of microplastics in benthic animals,the abundance of microplastics in the muscles tissue and visceral masses of the two snails was compared within the group.The results showed that there was no significant difference in the abundance of microplastics in muscle tissue and visceral masses.The abundance of microplastics in the gills of the Unio douglasiae is significantly greater than that of the muscle tissue.The abundance of microplastics in the sediment was 118 n·kg^-1 and 165 n·kg^-1of Wucheng Migratory Bird Sanctuary and Nanjishan wetland Nature Reserve,the microplastics abundance of Bellamya aeruginosa from Wucheng(1.1?1.3 items/g)is higher than that of Nanjishan(0.34?0.7 items/g).There was no significant difference in the abundance of microplastics between the muscles tissue and visceral mass.The microplastics in the two nature reserves are mainly fibers,the particle size is smaller than 1mm,accounting for the largest proportion.The polymer types include polystyrene(PS),polyethylene(PE),and polycarbonate(PC).Scanning electron microscopy-energy spectrum analysis results show that the surface of the microplastics is rough and has pores,which may be the result of the weathering in the environment and the digestion of the organism.There are many elements such as Ca,Na,and Si on the surface of the microplastics.Microplastics in nature reserves mainly come from the pyrolysis of plastics left over from fishing and tourism activities.The sediment microplastic abundance at the the estuary of Poyang Lake was 1475n·kg^-1 and the abundance of microplastics in the Bellamya aeruginosa was 2.42 items/g?2.99 items/g,which is higher than the abundance of five river estuaries and nature reserves.The microplastic fibers in the copper rust ring snails account for 70%of the total and are mainly colorless and transparent.The high abundance of microplastics in the study area may be due to the elongated shape of the lake outlet,which forces the microplastic particles to be concentrated in space.In addition,the confluence of the water from the Yangtze River carrying microplastics and the water from Poyang Lake slows down the lake flow,most of the suspended solids will settle to the bottom of the lake,which will also increase the microplastics in the sediments,thereby increasing the intake of microplastics by benthic animals.The overall abundance of microplastics in benthic animals in the typical area of Poyang Lake is as follows:estuary of Poyang Lake>five river estuaries>the nature reserve.The benthic microplastics in the study area are dominated by fibers.The approach of microplastics into benthic animals is not only affected by the shape,size,color and other factors of the microplastics,but also the physiological characteristics and living habits of the benthic animals will affect the ingestion of microplastics by organisms.In addition to the ingestion of microplastics by benthic animals,adhesion may be another way for microplastics to enter the benthic animals.