Pollution Characteristics And Source Analysis Of Microplastics In Different Environmental Media In Typical Areas Of Northwest China

Microplastics(plastic particles with individual diameter less than 5 mm)have been considered as an emerging pollutant which are ubiquitously present in various media of aquatic environment.Marked by their diverse sources,long existence in the environment,easiness of migration,capabilities in concentrating and transporting toxic pollutants,and potential to be ingested by auqatic biota due to their microscopic size,the presence and associated environmental risks of microplastics have aroused increasing concern.However,as the largest producer and user of plastics in the world,there is a serious lack of investigation and Research on the pollution of microplastics in China,especially in Northwest China.In this thesis,the surface water and sediment of Wuliangsuhai Lake,the indoor and outdoor atmospheric deposition in Shaanxi Province were selected as the research objects,the occurrence characteristics and sources of microplastics were investigated and analyzed.The research results provide data and theoretical support for the prevention and control of microplastic pollution in Northwest China,and further enrich the data of microplastics pollution in Northwest China.The main results are as follows.(1)Pollution characteristics of microplastics in the surface water of Wuliangsuhai Lake.The distribution characteristics of microplastics in 16 sampling sites of Wuliangsuhai sediment were investigated.Microplastic concentration in Wuliangsuhai Lake ranges from3.12 to 11.25 n/L,and that in five main canals rangs from 3.55 to 7.86 n/L.The different functional areas in Wuliangsuhai can be divided into four categories,namely effluent,fishing,intake and wetland areas.The highest microplastic concentration occurs in the intake area.Among the four functional areas of Wuliangsuhai Lake,the highest fiber concentration is observed in the fishing area.The microplastics in Wuliangsuhai Lake are mainly small size,and the microplastics smaller than 2 mm account for 98.2%of the total microplastics,while the microplastic size in the intake area is relatively large.Polystyrene and polyethylene are the main polymer types.Agricultural wastewater,domestic sewage and fishery discharge have the greatest impact on the microplastic distribution.This study reveals that the inland lakes in northern China are polluted by microplastics,which may cause potential harm to the surrounding environment.(2)Pollution characteristics of microplastics in the sediment of Wuliangsuhai Lake.The distribution characteristics of microplastics in 16 sampling sites of Wuliangsuhai Lake were investigated.It was found that the abundance of microplastics in surface sediments ranged from 16.5 to 72.4 n/100 g,and the surface sediments had obvious spatial distribution characteristics.The size and type of microplastics with the largest content were<0.5mm(74.39%)and fiber(53.95%).In order to study the vertical distribution of microplastics in Wuliangsuhai,four sampling points were selected and sampled with column sampler.The results show that the vertical variation trend of microplastics at different sampling points is basically the same.Even at the deepest(30 cm)depth of the collected sediment samples,microplastics were still present(2.33–8.67 n/100 g).The content of microplastics in sediments decreases with the increase of depth,and has a significant correlation with time,which is directly affected by human factors.Therefore,in estimating the storage of trace amounts of plastics in sediments,if only surface sediments are considered,the storage of trace amounts of plastics in the world may be underestimated.(3)Pollution characteristics of microplastics in indoor and outdoor atmospheric deposition in Shaanxi Province.The distribution characteristics of microplastics in indoor and outdoor atmospheric sediments in Shaanxi Province were investigated.It was found that the abundance of microplastics in outdoor atmosphere ranged from 97.6-349.6 n/(m~2d),while the abundance of microplastics in indoor environment ranged from 1.4×10~3-5.8×10~3n/(m~2d).The abundance of microplastics in indoor air is generally relatively high.It is proved that there are a large number of microplastics in the urban atmosphere.The abundance of microplastics varies greatly in different cities,which is related to the number of urban population.In the same city,the number of microplastics collected in residential area was the highest,followed by commercial area and industrial area.The abundance of microplastics in indoor atmosphere is related to indoor population density and human activity duration.