Study On Occurrence Characteristics Of Microplastics And Their Relationship With Algal Blooms In Chaohu Lake

In recent years,the pollution of microplastics(particle size<5 mm)has been the focus of scholars at home and abroad.It is very important to study the abundance level,distribution characteristics and migration mechanism of microplastics in different media to guide the pollution control of microplastics.Although research on microplastic pollution in marine and coastal environments has dominated to date,research on microplastic pollution in river and lake environments is increasing.Terrestrial input is one of the important sources of microplastics pollution,so it is of practical significance to study the occurrence characteristics of microplastics in inland freshwater environment.In this study,microplastics were extracted from the surface water and surface sediments of Chaohu Lake and its main tributaries.The abundance,shape,size and composition of microplastics in the samples were analyzed by means of microscopic examination and infrared spectroscopy.Population,economic and environmental data were collected and the flux into the lake was estimated.Based on satellite remote sensing images,the distribution and quantity characteristics of algal blooms in Chaohu Lake were simulated,and the relationship among the variables was studied by multivariate analysis method.It provides basic data and scientific basis for further research on microplastics pollution in fresh water environment.The main research results are as follows:(1)Microplastics were detected in water and sediment samples from 27 stations in Chaohu Lake,and the abundance of microplastics in Chaohu Lake was generally at a moderate pollution level.However,the abundance,composition and morphology of microplastics in different water periods and different media were different.The abundance of microplastics in water and dry season ranged from 240.00～6250.00 n/m3,with an average of 1796.30～2084.88 n/m3,respectively.The average abundance of microplastics in sediments was 280.00 n/kg in dry season and higher than in wet season.Different position in the water and sediment samples are distributed on flake,fibrous,granular and four forms of micro plastic film,but in the plentiful water is given priority to with flake and fibrous micro plastic,41.95%and 48.32%respectively,the mutagenicity fibrous micro plastic(76.51%)accounted for the highest,the sediments in the majority with fibrous and flake micro plastic,59.18%and 39.11%,respectively;The proportion of microplastics in water and sediment samples was slightly different,but the microplastics were mainly transparent and black,accounting for 23.80%,23.63%and 16.68%,24.05%,respectively.Abundant,water surface waters in the main components of micro plastic are Polyethylene Terephthalate(PET),46.27%and 71.70%respectively,but the mutagenicity of Polypropylene(PP)proportion is higher,at 21.73%,in the sediments polyethylene terephthalate(PET),at most 45.91%,compared with other components in the water,micro plastic,Polypropylene(PP)and Polyethylene(PE)ratio increased obviously,increased to 13.15%and 10.59%respectively.(2)From the perspective of the spatial and temporal distribution characteristics of microplastics in Chaohu Lake,the spatial variation of microplastics abundance in Chaohu Lake is great.Due to the disturbance of hydrology,meteorology,topography and human activities,the distribution characteristics of microplastics abundance in Chaohu Lake are generally higher at the mouth of the lake than in the lake,higher in the west than in the east,and higher in the north than in the south.(3)Based on the regional development index model,the flux of microplastics into the lake from 2014 to 2019 was estimated to be 98.52～111.36 t/a,which showed a decreasing trend.The flux of microplastics into the lake was mainly affected by human activities and runoff.(4)Based on satellite remote sensing image data against the performance of algae,summer and autumn(from April to October)is the outbreak of algae growth period,micro plastic characteristics of space-time distribution and the total phosphorus with similar characteristics and the distribution of the algae.In the early stage of algal bloom,the flux of microplastics into the lake was positively correlated with the algal density,while in the late stage,the flux of microplastics into the lake was negatively correlated with the algal density.