Study On Pollution Of Microplastics And Heavy Metals In Typical Rivers Entering Chaohu Lake

Since the 20th century,plastic products have been widely used in every field of life,which has provided great convenience for our life and work.But plastic waste is extremely difficult to degrade,a large amount of plastic waste enters the environment.In the long term physical,chemical and biological processes,plastic waste in the environment is slowly broken and decomposed into plastic particles with a diameter of less than 5 mm which are widely found in surface water,sediments,soil and organisms,which are called microplastics.Due to its characteristics of hard degradation,small diameter and large specific surface area,it is easy to adsorb pollutants in the environment,such as persistent organic pollutants and heavy metals.The adsorbed pollutants can accumulate through the food chain along with microplastics,which will seriously harm the natural environment and even human health.Therefore,as a new pollutant,microplastics have attracted much attention.In this study,microplastics were extracted from the surface water and sediment of typical rivers entering Chaohu lake-Nanfei River and Shiwuli River.The distribution characteristics and composition of microplastics were studied by using microscope and infrared spectrum.The contents of four heavy metals(Cd,Cu,Cr and Pb)in the sediments of two rivers were quantitatively analyzed using ICP-MS and ecological risk assessment was assessed.The main research results are as follows:(1)Quantitative analysis of microplastics at Nanfei River and Shiwuli River showed that microplastics particles existed in water samples and sediment of two rivers,the content of microplastics in the water sample of the Nanfei River was 833.3?4200 n/m~3,and the content of microplastics in the sediment was 330 n/kg?1363.3 n/kg.The content in the water sample of Shiwuli River is 183.3?2066.7n/m~3,and the content in the sediment is 83.3?710n/kg.The concentration of microplastics at Nanfei River was higher than Shiwuli River.In terms of spatial distribution,the microplastics are mainly concentrated in the middle reaches of Nanfei River,while the microplastics of Shiwuli River are concentrated in the lower reaches.According to the statistics of microplastic particle size,the content of microplastics in the water samples and sediments of Nanfei River and Shiwuli River decreased with the increase of microplastic particle size.(2)According to the statistics of microplastics types,the microplastics type of distribution in Nanfei River and Shiwuli River is similar,the highest proportion of water samples and sediments is fiber,followed by debris,particle and foam microplastics,and only the sediment particles in Nanfei River are higher than the debris microplastics.The color distribution of microplastics has a certain regularity,and the color microplastics account for the most,followed by transparent microplastics,white microplastics and black microplastics.However,the black microplastics in the sediments of the two rivers are all higher than the white microplastics.(3)The content distribution of the four heavy metals showed that the sediments of The Nanfei River mainly concentrated in the middle part of the river,while that of the Shiwuli River mainly concentrated in the upper part of the river.The analysis of the geoaccumulation index and the potential ecological risk index shows that Cd pollution in the sediments of the two rivers is high ecological risk and we should pay attention to it.