Study On The Correlation Between Microplastic Pollution And Eutrophication In Typical Lakes In The Middle And Lower Reaches Of The Yangtze River

In recent years,microplastics have attracted extensive attention from scholars at home and abroad as a new type of environmental pollutant.It has the characteristics of small particles,large number,and wide distribution.Microplastics have been found in most waters of the world,and them have also been found in the bodies of some marine organisms.Due to its small size and large specific surface area,microplastics can easily absorb persistent pollutants.In addition,some toxic substances carried by microplastics itself have seriously threatened the safety of marine life and ecological environment.Research on microplastics in China is concentrated in the sea area,and there are few studies on inland freshwater lakes,and most of freshwater lakes in China are in a serious eutrophication state.As an environmental pollutant,whether microplastics have a certain impact on lake eutrophication remains to be studied.In this study,18 important lakes in the middle and lower reaches of the Yangtze River in China were selected as the research area.The microplastics in the surface water and sediments of the lake were treated by the microplastic density separation method.Then,the treated microplastics were classified by microscopic examination for their abundance,shape,color and particle size,and the polymer composition of microplastics is analyzed by Raman spectrometer,and the distribution characteristics of microplastics in different lakes are preliminary analyzed.The water quality of 18 lakes was tested for total nitrogen,total phosphorus,chlorophyll and other indicators using the national standard method,and the nutritional status of each lake was calculated based on the chlorophyll concentration.Pearson correlation analysis was performed using SPSS20.0 software to further analyze the correlation between the nutritional status and the abundance of microplastics in the surface water and sediments of the sampled lake.The research results show that there are microplastic pollution in the surface water and sediments of 18 lakes in the middle and lower reaches of the Yangtze River in China,and the abundance range of micro-plastics in the surface water and sediments is 240-1800/m~3 and 90-580/kg,the average abundance of microplastics in surface water and sediments in all lakes is 780±429/m~3 and 219±124/kg.The lakes with the highest abundance of microplastics in surface water and sediment are honghu lake and south taizi lake in hubei province respectively.The microplastics in the surface water and sediment mainly exist as fibers.The amount of fibrous microplastics in surface water was up to93.81%,and that in sediment was up to 94.77%.In the surface water samples(40%-60%)and sediment samples(60%-80%),almost all lakes are dominated by blue microplastics,followed by purple and green microplastics.Surface water samples(40%-60%)and sediment samples(50%-80%)are mainly made of microplastics less than 1mm.Three polymers were identified,of which 60%to 80%of the surface water samples and 40%to60%of the sediment samples were polypropylene materials.The results of water quality testing of 18 typical lakes in the middle and lower reaches of the Yangtze river show that the lakes with the highest total nitrogen content are south taizi lake in hubei province,the lakes with the highest total phosphorus content are datong lake in hunan province,and chaohu lake has the highest concentration of chlorophyll a.The concentration ranges of total nitrogen,total phosphorus and chlorophyll a in all lakes are 0.5-4.5mg/L,0.0-0.5mg/L,5.0-113.9mg/m~3.According to the modified nutritional status index,the nutritional status of 18 sample lakes Carried out calculation evaluation.The results show that dianshan lake,taihu lake,chaohu lake,south taizi lake and honghu lake are in the important eutrophication stage.Pearson correlation analysis results showed that the abundance of microplastics in sediments was positively correlated with the total nitrogen concentration of the lake,and the nutrient status of the lake was independent of the abundance of microplastics in surface water and sediments.