Occurrences And Ecological Risks Of Micro (Meso) Plastics In Liao River Conservation Area

The problem of environmental pollution caused by microplastics has become the focus of worldwide attention.The widely distributed microplastics can cause physical damage by biological ingestion.The toxic substances and pollutants adsorbed on their surfaces also seriously endanger biological survival,population reproduction and ecological safety.In recent years,most studies have focused on the distribution,sources,and biological e ffects of marine water,sediments,and microplastics in living organisms.There are few studies on microplastic pollution nearby.The hydrological conditions of Liao River Conservation Area are susceptible to economic activities and are one of the most polluted rivers in China.Therefore,this paper takes Liao River Conservation Area as the research area,based on the principle of density separation,classifies and counts the shape,particle size,color and abundance of micro?meso?plastic,and the chemical composition was determined by micro Fourier transform infrared spectrometer??-FTIR?.Initially revealing the distribution characteristics,possible influencing factors and potential sources of micro?meso?plastics in the region,supplementing the basic data of microplastic pollution distribution in inland freshwater rivers and watersheds in China.On this basis,the pollution risk of micro?meso?plastics in different environmental media in Liao River Conservation Area was preliminarily evaluated by taking polymer type as evaluation index and combining with the hazard score of plastic polymer,which provided basic data and theoretical support for the establishment of a comprehensive risk assessment model and the pollution control of microplastics..The main findings are as follows:?Pollution characteristics of micro?meso?plastics in river surfacewater in Liao River Conservation AreaThe surface water bodies of 32 sites in Liao River Conservation Area were taken as the research object.Micro?meso?plastic pollution was prevalent in all sites,and the abundance range was between?0.02±0.03⁰.42±0.03?n·L^-1,with an average abundance of 0.11±0.10n·L^-1.Among them,Xinmin city?site L18?had the highest abundance of micro?meso?plastics in Shenyang city,followed by Changtu country?site L01?in Tieling city,and the lowest abundance was found in Kaiyuan city?site L10?.The surrounding environment of the sampling sites,such as tourism,fishery,logistics companies,plastic processing plants,clothing factories,sewage plants,residents'life and industrial activities,and the discharge of solid wastes and fiber-containing sewage,are the main reasons for the high micro?meso?plastic abundance in water.Micro?meso?plastic shapes were dominated by debris?46.00%?,followed by fiber?30.14%?and film?16.57%?.The minimum particle size of micro?meso?plastics was 143?m,and was mainly in size fraction<1000?m?38.01%?.The color of micro?meso?plastic was dominated by blue?43.89%?,followed by black and white.A total of16 components were detected in water,with Rayon?56.11%?being the most abundant,followed by PES?19.46%?and PET?7.69%?.Rayon,PES and PET micro?meso?plastics were mainly fibrous?>90%?,while PE was mainly in the shape of film and fiber?50%each?,PP in fiber?50%?,film?25%?and debris?25%?.In summary,domestic sewage containing synthetic fibers discharged from washing wastewater of surrounding residents,widely used fishing nets,fishing lines and industrial wastewater discharge may be potential sources of fibrous micro?meso?plastics in surface waters.Compared with other studies at home and abroad(surface water 0.33⁵45.00 n·m^-3),the pollution level of micro?meso?plastics in river water in Liao River Conservation Area is at a low level.?Pollution characteristics of micro?meso?plastics in river sediments in Liao River Conservation AreaMicro?meso?plastic contamination is prevalent in surface sediments of all sites,and the abundance of micro?meso?plastic varies significantly from each site,ranging from?6.67±1.15²40.00±52.92?n·kg^-1,with an average abundance of?62.29±54.30?n·kg^-1.Among them,the highest abundance of micro?meso?plastics appeared in Xinmin city?site L19?,followed by Shenbei new district?site L17?,and the lowest abundance appeared in Tai'an county?site L27?.Factors such as industrial activities?plastic processing and processing,post office and express logistics,clothing?,agricultural activities?planting,animal husbandry and aquaculture?,sewage discharges?domestic sewage and industrial wastewater?,and population density all contribute to the level of micro?meso?plastic pollution in sediments.The majority of micro?meso?plastic shapes were fiber?43.48%?,followed by debris?24.41%?and film?20.40%?.The minimum particle size of micro?meso?plastics was 147.3?m,and was mainly in size fraction<1000?m?36.46%?.White was the most popular colour?39.13%?,followed by yellow,black and blue.A total of 27 kinds of microplastics were detected in the sediments,Rayon was the mainly type?32.44%?,followed by PS?19.46%?,SBS?7.02%?,PA?6.69%?,PET?4.01%?,PP?3.34%?and PE?2.34%?.Among them,Rayon,PES and PET are mainly in the shape of fiber,PA and PP are mainly in the shape of debris,PE is mainly in the shape of film and PS is mainly in the shape of foam.Household decoration,cosmetic packaging,foam buoys in the manufacturing industry and aquaculture,the disposal of fishing activities?nets,fishing gear,ropes?,domestic sewage from coastal settlements and industrial wastewater from factories may be potential sources of micro?meso?plastics in river surface sediments.Compared with other studies at home and abroad(0.07².58 n·g^-1),the pollution of microplastics in river sediments in Liao River Conservation Area is at a low level.?Pollution characteristics of micro?meso?plastics of soil in Liao River Conservation AreaThe soil near the river in 32 sites was taken as the research object,and micro?meso?plastics were observed in all sites,with the abundance between?13.33±11.55⁸86.67±133.17?n·kg^-1,and the average abundance between?145.83±211.46?n·kg^-1.Among them,the highest abundance of micro?meso?plastics appeared in Taian county?site L27?,followed by Xinmin city?site L21?,and the lowest abundance appeared in Yinzhou district?site L12?.High abundance micro?meso?plastics may be generated at both sites due to dense villages,express delivery companies,plastic factories,clothing factories,and agricultural activities?plastic film mulching,sewage irrigation,sludge composting?.The shapes of micro?meso?plastic were dominated by debris?46.00%?,followed by fiber?30.14%?and film?16.57%?.The minimum particle size was 88?m,and the proportion of micro?meso?plastics with particle size<1000?m was 39.57%.The main color was white?46.86%?,followed by black?12.71%?,yellow?11.14%?and blue?11.00%?..A total of 27 components were detected in the soil,the main type was PP?41.71%?,followed by Rayon?20.14%?and PE?13.86%?.Among them,PE and PA are dominated by films,and the proportion is close to?PE;58.76%,PA:57.14%?.PP was dominated by debris?85.62%?,PS by foam?95.24%?,PES,PET and Rayon by fiber?85.00%?.Plastic products?pesticide bottles,fertilizer packaging bags,woven bags,plastic agricultural film?,sewage discharge and irrigation,used for packaging,decorative foam materials are the main sources of soil micro?meso?plastic.Compared with other studies at home and abroad(?320 n·kg^-1),the pollution of river sediment micro?meso?plastics in Liao River Conservation Area is at a medium low level.?Comparative analysis of distribution and abundance of micro?meso?plastics in three environmental media of Liao River Conservation AreaIn this study,the micro?meso?plastic abundance in the so il of Liao River Conservation Area was commonly higher than that in the freshwater water and sediments in the area.The extremely high value of micro?meso?plastic abundance in river surface water and sediment appeared in Xinmin city,Shenyang city,while the extremely high value in soil samples appeared in Tai'an county of Anshan city.The spatial distribution of micro?meso?plastics is influenced by geographical location,human activities and surrounding environment.The abundance of micro?meso?plastics at the stations in the tributary estuaries was higher than that at the stations in the adjacent non-estuarine main flow,indicating that the upstream transport of the river had a certain contribution to the micro?meso?plastics abundance in the estuaries.There are similarities and differences in the distribution of the shape,composition,color and particle size of micro?meso?plastics in various environmental media.In the three environmental media,the micro?meso?plastic shapes are dominated by fiber,debris and film,among which,river surface water and sediment are dominated by fiber,while soil is dominated by debris.In terms of composition,Rayon is the most micro?meso?plastics in water and sediment,while PP is the most micro?meso?plastics in soil,followed by PE.The high proportion of these two materials may be closely related to the high proportion of debris.In terms of particle size,the three environmental media are mainly<1 mm.In the three environmental media,Rayon,PES and PET are mainly in the shape of fibrous,PE,PE/PMP and POA are mainly in shape of film,PS is mainly in shape of foam,and?PAN?PAN/PAA is mainly in shape of fiber.While PA in water is mainly in shape of fiber,in sediment and soil are mainly debris and film.PP in water is dominated by fiber,while in soil and sediment is debris.The rich shape and composition of PP increases the ecological risk of micro?meso?plastic in the environment.?Preliminary study on ecological risk assessment of micro?meso?plastic pollution in Liao River Conservation AreaThe ecological risks of micro?meso?plastics pollution in three environmental media in the study area were preliminarily discussed.Pearson correlation analysis showed that there was no correlation between the abundance of micro?meso?plastics in water,sediment and soil and the risk index?P>0.05?,which may be the result that the risk index varies greatly due to the large span of each sampling point,the different sources and distribution characteristics of micro?meso?plastics pollution.