Distribution And Characteristics Of Microplastics In Global Water And Sediments

As a new type of pollutant,microplastics have received much attention in recent years.The number of research articles on microplastic pollution is also growing rapidly,but it is still in the exploration stage,and the research on microplastic pollution in the literature generally only focuses on a local area.It is conducive to the formation of a standardized survey process,the discovery of research gaps and problems,and the distribution of microplastic pollution from a global perspective to summarize and evaluate the research articles in a timely manner.In this study,329 research articles on microplastic pollution published before2020 were collected and screened from Web of Science.Time of publication,country of sampling,type of sampling location,sample type,latitude and longitude of sampling location,sampling tool,sampling depth,whether to record wind speed,method of microplastic extraction,Whether to carry out polymer type identification and detect polymer type and main polymer type,whether to carry out size classification and proportion of each size,whether to carry out microplastic shape judgment and main form,whether to carry out microplastic color judgment and main color and other information were collected and the following analysis was conducted:The basic information of the microplastics pollution survey literature is analyzed.The publication time of the literature and the analysis of the country have found that the literature on microplastic pollution has increased rapidly in recent years,and the literature distribution is relatively concentrated,and some regions lack reference data;The amount of literature was discussed in conjunction with the total research and development expenditure of each country and the number of people directly engaged in research and development.The quantity of literature related to freshwater environment and seawater environment is compared.The seawater-related research is1.7 times that of freshwater,which shows that the research on microplastic pollution in freshwater is weak.The investigation process of microplastic pollution was analyzed.The main steps in the entire process of microplastic pollution investigation: sampling tools,whether to use density separation and density separation solutions,whether to carry out organic matter digestion and digestion liquid,and whether to analyze the four characteristics,the microplastics concentration unit was counted.The investigation process of microplastic pollution was analyzed.The main steps in the entire process of microplastic pollution investigation: sampling tools,whether to use density separation and density separation solutions,whether to carry out organic matter digestion and digestion liquid,and whether to analyze the four characteristics,the microplastics concentration unit was counted.The most used unit of microplastic concentration in water is n/m3,and the most common unit in sediment is n/kg.The pollution distribution of microplastics was analyzed.The literature of the unit of microplastic concentration in water is n/m3,and the literature of sediment in unit of n/kg is counted and the magnitude of the microplastics concentration was visualized using Arc GIS.In general,the concentration range of microplastics is very large,0.031 n/m3 ? 88000 n/m3 in water,and 0.75 n/kg ? 7960 n/kg in sediment.The microplastic pollution levels in in the two regions where the literatures were concentrated,China and the Mediterranean,were similar to the global microplastic pollution levels,and there was no statistical difference in the concentration of microplastics in the study period.The characteristics of microplastics are analyzed.The literatures of carrying out polymer type identification and size classification were selected to analyze the detected polymer types,main polymer types and main sizes in water and sediments.There are many types of polymers detected by microplastics,with 46 in both water and sediment,and the detected types have a very high consistency.The main polymer types in water and sediments are PE and PP.The other main polymer types are similar.There is a slight difference in the frequency due to the difference in the sedimentation performance of microplastics.For example,PET appears as the main polymer type in sediments more frequently than water.The size of microplastics is mainly distributed in small size microplastics <1 mm,so the mesh size used in the process of adopting or extracting microplastics will have a greater impact on the results.Microplastics with larger sizes are more distributed in the Mediterranean region And ocean regions.The relationship between size,shape and color of microplastics and polymer type was studied,but no obvious correlation was found.