Distribution Patterns Of Microplastics In Lakes Affected By Different Human Activitie

Plastics are widely used because of their extensibility,durability and low cost.As the production and use of plastic increases,so does the amount of plastic waste.As a completely man-made material,plastic will cause different degrees of harm to the ecosystem after being discharged.Lake is an important ecosystem in the environment.And the distribution of microplastics in lakes can effectively reflect the pollution level of microplastics in the study area.At present,researches on lake plastic pollution are mainly focused on the eastern and coastal areas,and little attention has been paid to the southwest of China.Therefore,this paper takes Aha Lake in Guiyang City,Guizhou Province,southwest China as the research area,and investigates the pollution of microplastics in surface water and columnar sediments through physicochemical characteristics such as abundance,particle size,color,shape,and polymer composition information.The distribution characteristics of microplastics in surface water and columnar sediments in the study area were revealed,and the potential sources of microplastics were explored based on the microplastics diversity index.（1）From the perspective of abundance,microplastics were found in surface water and columnar sediment samples of Aha Lake.The average abundance of microplastics in surface water and sediment was 608.33 items/m³ and 648 items/kg（dry weight）,respectively.The highest abundance of microplastics in surface water and sediment samples was found in the entrance of Jinzhong River,and the lowest abundance was found in the middle of the lake.In brief,the abundance of microplastics was low near the lake center and high near the shore,indicating that tributary input was the main pathway of microplastics in Aha Lake.（2）In terms of physical characteristics,microplastics in surface water and columnar sediment samples of Aha Lake are mainly in small size.The microplastics of<1000μm accounted for 78.08%and 78.45%in surface water and columnar sediments,respectively.In general,the smaller the particle size of microplastics,the higher the abundance.In terms of shape,microplastics in surface water and sediment are mainly fibers and fragments.In terms of color,transparent,green and blue are the main colors,and the colors are more abundant in the sampling sites of the entrance to the lake of Jinzhong River and Ya River,which are relatively densely populated.（3）In terms of polymer composition,the proportion of polymer types in surface water from high to low is:Pigment（31.51%）>polyester（PES,19.18%）>polypropylene（PP,15.07%）>polyurethane（PU,12.33%）>polyethylene（PE,10.96%）>Polystyrene（PS,2.74%）,while in sediments polypropylene（35.09%）>Pigment（22.31%）>Non-plastic（13.53%）>Polyurethane（11.53%）>polyethylene（10.03%）>polystyrene（4.51%）>polyester（3.01%）.Their distribution ratio is slightly different in different environmental media,which is related to the properties of microplastics themselves（such as density,size,shape,etc.）and water environmental factors.（4）The sources of microplastics in surface water and sediment of Aha Lake were analyzed by combining hydrochemical characteristic parameters and microplastics diversity index(including shape diversity index(D_shape),color diversity index(D_color),size diversity index(D_size)and comprehensive diversity index（MDII）.The results showed that the microplastics in Aha Lake were mainly affected by the discharge of surrounding pollution sources,mainly from urban human activities and agricultural production activities,and the waste water from abandoned mine had almost no effect on the microplastics.Moreover,the comprehensive diversity index has a good indicator effect on the intensity of human activities in the tributaries of Aha Lake.