Study On The Occurrence Characteristics Of Microplastics In Lake Water And Sediment In Inner Mongolia Plateau

In the context of the continuous increase of the total production of disposable plastic products,microplastic pollution has become a global focus of environmental concern.Microplastics are difficult to recycle and degrade,posing risks to the ecosystem and public health,especially to the fragile lake ecological environment in The Inner Mongolia Plateau.It has great significance to fully understand the occurrence characteristics of microplastics in lake environment of Inner Mongolia Plateau region for reflecting the pollution level of microplastics in aquatic environment of arid and semi-arid area in northwest China.Therefore,this study selected 17 lakes of Inner Mongolia plateau as the research objects,water and sediment samples are collected for pre-treatment,quantitative and qualitative analysis was performed by fluorescence microscopy,assem and microraman spectroscopy,The abundance,shape,color,particle size,composition and other occurrence characteristics of microplastics in lake water and sediment were determined,the distribution law of microplastics was analyzed.The correlation between the abundance of microplastics and lake environmental factors was investigated.The main results are as follows:（1）The average abundance of microplastics in lake water of Inner Mongolia Plateau is（5.57±4.02）items/L,which is at a medium and high level in the national aquatic environment.The abundance range was 0.19-12.64 items/L,and the overall spatial distribution trend was higher in central Inner Mongolia and lower in eastern and western Inner Mongolia.Polypropylene（49.13%）and polyethylene（16.78%）were the main types of microplastics.Microplastics of 50-200 μm accounted for 62.37%.Block（39.72%）,strip（19.51%）and fiber（15.33%）were the main shapes of microplastics.The color is mainly transparent（70.03%）.Microplastics in lakes of The Inner Mongolia Plateau are mainly characterized by small size transparent block fragments,which are closely related to the weathering conditions with strong ultraviolet radiation and long sunshine duration in the plateau area.（2）Sediment is the main trend of microplastics in lakes.The average abundance of microplastics in sediments of Lakes on the Inner Mongolia Plateau is（128.29±77.63）items/kg,which is higher than that of lakes in other remote western regions.The abundance ranges from 25 to 400 items/kg,with a gradually decreasing distribution pattern from the east to the west of the Inner Mongolia Plateau,and has no significant correlation with the abundance distribution of microplastics in water bodies.The main components of microplastics in sediment are polypropylene（36.36%）and polyethylene terephthalate（23.18%）.The proportion of microplastics larger than 500 μm was 51.37%.The main colors were blue（37.27%）and black（25.91%）.The shape is mainly fiber（67.73%）.Microplastics in lake sediments of Inner Mongolia Plateau are mainly characterized by large-size blue or black fibers,indicating that fibrous microplastics with larger density and particle size in water are more likely to accumulate in sediments.Combined with the field investigation and analysis,it was found that the microplastics in plateau lakes of Inner Mongolia mainly come from domestic laundry wastewater,farmland water withdrawal and tourism activities.（3）There was a significant positive correlation between the abundance of microplastics and pb concentration in lakes in eastern Inner Mongolia（P<0.01）,was significantly positively correlated with total organic carbon concentration（P<0.05）,indicating that there may be homologous or compound pollution of microplastic abundance with lead and organic matter.There was a significant negative correlation between the abundance of microplastics and dissolved oxygen concentration（P<0.05）,which is related to the degradation of oxygen-consuming organic matter associated with microplastics.There was no significant correlation between microplastics abundance and physicochemical properties of sediments.The microplastics abundance in salt lake sediments was significantly higher than that in salt lake and fresh lake（P<0.05）.The microplastics abundance in grassland lake water was significantly higher than that in other lakes,and the microplastics abundance in desert lake sediment was significantly higher than that in other lakes.It is mainly influenced by human activities such as grazing,sewage discharge,tourism and natural environmental processes such as salt deposition and vegetation interception in different types of lakes.