Research On The Characteristics Of Microplastic Pollution In Nansi Lake Water

Microplastics refer to plastic particles with a diameter of less than 5mm,because it exists widely in the environment and can enter organisms through the food chain,causing direct or indirect effects on organisms,it has been widely concerned by countries all over the world in recent years.At present,the application of plastic products in China is very common.All kinds of plastic products gradually become small diameter microplastics into the water body by weathering and wear and become one of the water environmental pollution problems.Nansi Lake is located in the southwest of Shandong Province.It is one of the important storage lakes in the east route of Southto-North Water Diversion Project of China.The quality of the water environment is directly related to the production and life of the people in the Beijing-Tianjin-Hebei region and Shandong Jiaodong region.At present,there is no report on the research of microplastic pollution in the water of Nansi Lake.In this study,4 lake areas of Nansi Lake and the inlets of 11 main rivers entering the lake were selected as the study sites.Surface water,sediments,and a small amount of aquatic organisms(fishes,shrimp)in the lake area were collected during the dry season(December 2019)and wet season(July 2020)to study the characteristics of microplastic pollution in the water body.We use density flotation,vacuum filtration and biological digestion methods to separate the microplastics in the sample,classify and count the microplastics under a stereo microscope,identify the microplastics with a Raman spectrometer,and use the scanning electron microscope to qualitatively analyze the surface structure characteristics of the microplastics.The purpose is to analyze the current status and characteristics of microplastic pollution in different lake areas and different inlets of Nansi Lake;Compare the differences in microplastic pollution characteristics in Nansi Lake during wet and dry season;Explore the accumulation of microplastics in aquatic organisms preliminarily.It is expected to provide a reference for subsequent research on the characteristics of microplastics pollution in water bodies,and to provide basic data for the prevention,control and treatment of microplastics pollution in water bodies in the future.The main results of this study are as follows:(1)The concentration of microplastics in the surface water of Nansi Lake and the main entrance of the lake varies significantly in different hydrological periods,and the dry season is significantly greater than that of the wet season(P<0.01).The concentration range of microplastics in surface water during dry season is 1.17 ～ 10.12items/L,with an average concentration of 3.42 ± 2.89 items/L;The concentration of microplastics in surface water during dry season ranges from 0.32 to 3.65 items/L,with an average concentration of 1.05 ± 1.00 items/L.There are obvious differences in the concentration of microplastics in the surface water of each sampling site.For example,the concentration of microplastics in the surface water of the Baima River estuary in the dry season(6.70 items/L)is significantly higher than that of the Sihe River estuary(1.57 items/L)(P < 0.01).The particle size,color,shape and other composition characteristics of microplastics in the surface water during the wet and dry seasons are similar and the microplastics are mainly those with smaller particle size(0 ～ 500μm);The colors are mainly blue,gray,black and transparent;Fibrous microplastics account for the highest proportion of microplastics of different shapes.(2)The concentration of microplastics in the sediments of Nansi Lake and the main lake entrances differed significantly in different hydrological periods,and the dry season was significantly greater than that in the wet season(P<0.01).The concentration of microplastics in the sediments of all sampling sites during the dry season ranged from 97.78 to 755.55 items/kg(dry weight),and the average concentration was 266.67± 225.70 items/kg(dry weight).The concentration range of microplastics in the sediments of all sampling sites during the wet season is 80.00 ～ 426.67 items/kg(dry weight),and the average concentration is 177.48 ± 127.95 items/kg(dry weight).There are significant differences in the concentration of microplastics in the sediments of each sampling site.For example,the concentration of microplastics in the sediments of the Chengguo River estuary in the dry season(755.55 items/kg)is significantly higher than that of the Zhuzhaoxin River estuary(97.78 items/kg)(P < 0.01).The particle size,color,shape and other composition characteristics of the microplastics in the sediments in the wet and dry seasons are similar.The microplastics are mainly those with smaller particle diameters(0 ～ 1000μm);The colors are mainly blue,gray,green and transparent;Fibrous microplastics account for the highest proportion of microplastics of different shapes.(3)There are certain differences in the accumulation of microplastics in aquatic organisms in the Nansi Lake area in different hydrological periods.The microplastics in shrimps during the dry season were 1.33 items/individual more than 0.83items/individual during the wet season;The microplastics in fishes during the dry season were 3.00 items/individual more than 2.06 items/individual during the wet season.The particle size,color and shape composition of microplastics in fishes and shrimps are consistent with the composition of microplastics in surface water and sediments.(4)Through the analysis of Raman spectroscopy,we found three kinds of microplastics with chemical composition in Nansi Lake and the main entrance of the lake,namely PP,PET and PE.There are different degrees of weathering or wear marks on the surface of various types of microplastics,and heavy metals and other pollutants are often attached to the microplastics surface.In general,the microplastic pollution in the waters of Nansi Lake during the dry season is more serious than that during the wet season.There are spatial differences in microplastic pollution between different lake areas or lake entrances.The accumulation of microplastics in aquatic organisms(fishes and shrimps)is directly related to the microplastics in the water.The overall particle size of the microplastics in the waters of Nansi Lake is relatively small.There are more blue,gray,black,green and transparent microplastics.Fibrous microplastics are the main composition type.