Study On Microplastic Pollution Characteristics And Ecological Risk Assessment In Manas River Basin

Microplastics is a new type of pollutant in the environment.In recent years,it has been widely found in various environmental media.Because microplastics have a wide range of sources,small size,light weight,easy to be swallowed by organisms,long periods in the environment,easy migration under environmental forces,and the ability to enrich and transport coexisting pollutants in the environment,it will have an ecological environment Various influences have attracted widespread attention from related researchers.In recent years,domestic and foreign research on microplastic pollution in the water environment has focused on the marine environment,and research on the characteristics of microplastic pollution in inland rivers is still scarce.China is the world's largest plastic producer,and survey data on the status of microplastics pollution in freshwater environments are severely lacking.In addition,due to the large specific surface area of microplastics,it can be used as a carrier to adsorb organic pollutants in the water environment,and produce a compound pollution effect on the water environment,thereby seriously endangering the health and safety of the ecological environment.By exploring the characteristics of the composite pollution of microplastics and organic pollutants in the environment,it has important reference significance for further understanding the ecological and environmental risks of microplastics.At present,China's investigation on the spatial and temporal distribution characteristics and ecological risk of microplastics pollution in freshwater systems is still in its infancy.There is no accurate microplastic concentration to define its potential ecological risk to the environment.Therefore,in this study,the Manas River in northwestern China was selected as the research object.The qualitative and quantitative aspects of the spatial and temporal distribution of microplastic pollution in the surface water of the Manas River Basin in different seasons were preliminary explored.In the experiment,the composite pollution behavior characteristics and potential mechanism of hydrophobic organic pollutants in microplastics and environment were studied.At the same time,taking the Manas River as an example,different evaluation methods were used to analyze and evaluate its potential ecological risks.The main findings are as follows:(1)The abundance of microplastics in the surface water of the Manas River Basin is 6±2–48±9 items/L.Fibrous microplastics dominated all samples(86.2%).Their size is mainly distributed between 0.1-1.0mm(87.55%),with white and black being the main colors.In addition,the subject also studied the area distribution characteristics of sheet microplastics,mainly between 2.5×10~3–9.0×104?m~2(81.49%).Infrared spectroscopy analysis showed that most of the selected particles were identified as microplastics,and the polymer type of microplastics was mainly composed of polypropylene and polyethylene terephthalate.There are seasonal changes in the characteristics of microplastic pollution.The study can be used as a reference to better understand the pollution characteristics of microplastics in inland rivers.(2)The adsorption equilibrium concentration of PA for norfloxacin is 1.33 mg/g,and the adsorption equilibrium concentration of PVC for norfloxacin is 0.59 mg/g.For the adsorption capacity of norfloxacin,PA is higher than PVC.The adsorption kinetics of norfloxacin on polyamide and polyvinyl chloride particles conforms to a quasi-second-order kinetic model(R~2>0.991),and the adsorption rate of pollutants by the adsorbent is controlled by the intra-particle diffusion.Isothermal adsorption experiments show that the Freundlich model can better fit the isotherm(R~2>0.970)compared to the Linear model and Langmuir model.The adsorption capacity of polyamide to norfloxacin is significantly higher.(3)The evaluation results of the microplastic compound composition index method and potential ecological risk method are affected by the size of the polymer's toxicity score.The entire research area belongs to the serious pollution level.There is seasonal variation in the evaluation index and the degree of polymer pollution,among which PVC and PC have the highest levels of pollution.The results of using the pollution load index method show that the study area is of a slight degree of pollution in all four seasons.