Distribution,enrichment And Ecological Risk Assessment Of Microplastics In Wild Fish In Songhua River

As a new pollutant,microplastics exist widely in aquatic environment.It has the characteristics of persistence,bioaccumulation and long-distance transportation,which can be taken up by wild fish and transferred along the food chain,pose an own risk to the growth and development of wild fish and human health.Therefore,the study on the content and characteristics of microplastics in wild fish is of great significance to the assessment of the relationship between microplastics and wild fish in water environment,the control of microplastics content in water environment and ecological risk assessment.However,most studies on the effects of microplastics on wild fish have focused on the feeding process,studies on the distribution of microplastics in the skin,gills,tisane organs of wild fish and the relationship between microplastics and water environment are limited,which makes it difficult to evaluate the potential ecological risk of microplastics in water environment.In order to solve these problems,this paper analyzes 14 sampling sites in the main and tributaries of Songhua River,taking the wild fish in the waters of Songhua River as the research object,accumulation of microplastics in gills,intestines,toss and scales(skin),shape,color,composition and particle size distribution of five typical wild fishes,the occurrence characteristics of microplastics in the waters of the Songhua River in the active area of wild fish were analyzed,and then the relationship between microplastics in the waters of Songhua River and fish was analyzed.The accumulation of microplastics in fish and its effect on fish feeding were investigated by laboratory simulation experiments.The whole process from ingestion to accumulation,from microplastics in natural water to the correlation of microplastics in wild fish was analyzed,and finally the ecological risk assessment of microplastics was realized.The results of the above study are as follows:(1)the study found that the content of microplastics in the river water in the main stream of Songhua River was higher than that in the tributaries,and was affected by the content of microplastics in the river water,the amount of microplastics accumulated in the wild fish in the main stream was greater than that in the tributaries.For different species of fish,the accumulation of microplastics in fish gills and intestines was as follows: Crucian Carp ? GT;White Minnow ? GT;Stickleback ? GT;Pike ? GT;Catfish ? GT,the accumulation of microplastics in fish toss was mainly affected by the accumulation of microplastics in Gills and intestines,and showed a positive correlation.It was found that the amount of plastic accumulated on the surface of fish with scale structure was higher than that of fish without scale structure.(2)there are 4 kinds of microplastics in the body of Crucian carp,White Minnow,trichiurids Haumea,Pike and catfish in different sampling sites in Songhua River.The proportion of sheet microplastics in Gills,intestines,toss and scales(skin)was the highest(54.6%),followed by linear microplastics(25.7%),microsphere microplastics(11.2%)and fibrous microplastics(8.5%).The results showed that white and colorless microplastics were dominant in the gills of wild fish,and the content of color microplastics was less.(3)eight microplastic chemicals were found in the river water of the main Songhua River,they are polypropylene(PP),polyethylene(PE),polystyrene(PS),Polyethylene terephthalate,polyvinyl chloride,polybutene(PB),polyamide(PA)and poly(methyl methacrylate).Six microplastics,polypropylene(PP),polyethylene(PE),polystyrene(PS),Polyethylene terephthalate,polyvinyl chloride and polyamide(PA),were found in tributaries of the Songhua River.The main chemical compositions of microplastics in wild fish were polypropylene(PP),polyethylene(PE)and polystyrene(PS),which indicated that the microplastics of these three materials were more easily to enter the wild fish.It can also be inferred that in the main and tributaries of the Songhua River,the greater probability of entering the organism is due to the contamination of the river with polypropylene,polyethylene and polystyrene microplastics.The types of microplastics in wild fish are directly related to the types of microplastics in river water.(4)the size distribution of the plastic particles in the body of wild fish is larger than0.3 mm.It can be inferred that the microplastics with larger particle size cannot be easily excluded from the body,and the larger particle size cannot be found in the part of the fish tissue.There are many kinds of microplastics in gills and scales(skin),which may be related to the microplastics in river water.In fish intestines,the species did not change much,the particle size changed obviously,and the amount of microplastics with large particle size decreased.Only small-sized microplastics are present in fish toss and they are few in variety and quantity.Polypropylene and polyethylene are ubiquitous in the samples,followed by polystyrene.(5)in the laboratory simulation experiment,it was found that the amount of microplastics accumulated in the Gill of Carassius auratus was the most,and the amount of microplastics accumulated in both polypropylene and polyethylene was more than 100 Mesh for 200 Mesh.The microplastics of 200 Mesh could not be digested or excreted easily,the smaller the plastic particle was,the easier it was to get rid of the body,and polypropylene was easier to get rid of than polyethylene.Microplastics are far more in the fish than they are out.The kinds of microplastics had little effect on the selective feeding of Carassius auratus,but had little effect on the body length of Carassius auratus.(6)there was no significant difference in the PLI Val between the mainstream and the tributaries,but the Ply index of the mainstream river was significantly higher than that of the tributaries,which might be attributed to the fact that the Ply index of the mainstream river was higher than that of the tributaries.The key factors of high potential ecological risk in the study area,from high to low,were PP,PE,PS,PET.From the concrete numerical point of view,the ecological risk index RI of many kinds of micro-plastic polymers and Ear of single polymer show a certain relationship.Based on the above results,the distribution characteristics of microplastics in gills,skin and body tissue wild fish in Songhua River Songhua River were studied.The particle size,composition and morphology of the micro-plastics are all related to the occurrence of the micro-plastics in the water environment of Songhua River.There was a positive correlation between the amount of microplastics in fish and the amount of microplastics in water.Controlling the amount of microplastics in water would have a direct effect on reducing the amount of microplastics in wild fish.The amount of 200 Mesh micro-plastics accumulated by fish is the most,and it is not easy to be discharged.The potential ecological risk of Pp micro-plastics is the highest,and the potential risk of human health is the greatest.