微塑料通常指粒径小于5 mm的人造聚合物微粒，已在全球海洋、淡水、土壤、生物体等多种介质中被检出，其造成的环境污染和健康影响引起广泛关注。城市是人类活动最集中的区域，微塑料污染风险高、管控难度大。针对城市水环境中微塑料分布、来源不明确，微塑料与城市人类活动关系不清晰的问题，本文通过对“河流（苏南运河）流经区域-典型城市（苏州城区）-城市重点区（苏州古城）-城市内典型排放源”进行研究，掌握了苏南地区水体中微塑料赋存特性，分析了微塑料排放影响因素，研究了城市地区典型微塑料有组织和无组织排放源特性，并通过多元分析方法识别了苏州城区城市水体中微塑料主要来源。主要成果如下。系统分析了苏南地区水体微塑料浓度范围和多尺度空间分布状态。苏南地区人口密集、经济发达，水体微塑料浓度与世界主要城市群处于同一水平。苏南运河水体微塑料浓度为3.41 ~ 19.07个/L，平均9.59 ± 3.95个/L；苏州城区水体微塑料平均浓度为15.04 ± 12.10个/L，苏州古城为19.00 ± 7.72个/L；微塑料主要以碎片形式存在，绝大多数微塑料小于100 μm；苏南运河水体中占比最高的聚合物为聚对苯二甲酸乙二酯（PET）、聚碳酸酯（PC）和聚乙烯（PE），苏州城区占比最高的为聚丙烯（PP）、氯化聚乙烯（CPE）和聚碳酸酯。揭示了不同尺度下水体微塑料分布的关键影响要素。在河流流域尺度上，运河水体微塑料浓度与沿河城市社会经济发展水平密切相关，流经城市后苏南运河水体微塑料浓度增加26% ~ 211%。在城市尺度上，河道垃圾量和城区开发水平与水体微塑料丰度呈正相关，不同土地使用类型的微塑料贡献依次为旅游区＞商业区＞公共用地＞居民区＞交通用地。发现了不同污水处理工艺对于不同种类微塑料的去除能力存在明显差异，以及排水系统对微塑料的截留作用规律。苏州城区主要污水处理厂出水微塑料浓度范围为13.87 ~ 32.93个/L，相对于进水减少29.73% ~ 82.90%。PP在污水厂中有较高的截留率。污水厂和排水管网中使用的塑料制品会造成微塑料的释放。无组织排放是城市水体微塑料的主要来源。典型微塑料无组织排放源苏州城区排水管道淤泥中微塑料的浓度范围为13.8 ~ 107.4个/g干重。影响微塑料无组织排放的城市因素包括：民居类型、水上活动、绿化水平、交通强度。PC和PET类制品易通过无组织排放方式进入水环境，应加强其使用和废弃过程中的管理。
Microplastics, commonly referred to as plastic particles with a size of less than 5 mm, have been detected in a variety of media such as marine, freshwater, soil, and living organisms around the world. Cities are the areas where human activities are most concentrated, and the risk of microplastic pollution is high and it is difficult to control. Aiming at the problems that the distribution and source of microplastics in the urban water environment are not clear, and the relationship between microplastics and urban human activities is not clear, this paper studied the storage characteristics of microplastics in water bodies in southern Jiangsu by studying the " region - typical city - key urban area - typical emission source in the city", analyzed the influencing factors of microplastic emissions, and studied the characteristics of typical microplastics organized emission sources and fugitive emission sources in urban areas. The main sources of microplastics in urban water bodies in Suzhou were identified by multivariate analysis methods.The concentration range and multi-scale spatial distribution of microplastics in water in southern Jiangsu Province were systematically analyzed. The results show that the microplastic abundance in the water of Southern Jiangsu, with a dense population and developed economy, is at the same level as that in major urban agglomerations in the world. The abundance of microplastics in the water of the Southern Jiangsu Canal is in the range of 3.41 to 19.07 particles/L, with an average of 9.59 ± 3.95 particles/L. The abundance of Suzhou Urban Area is in the range of 3.90 ~ 91.62 particles/L, with an average of 15.04 ± 12.10 particles/L. The microplastics in Suzhou Ancient City all come from fugitive emission, with an average abundance of 19.00 ± 7.72 particles/L (5.28 to 68.56 particles/L). Fragment is the main shape of microplastics. Most of the microplastics are less than 100 μm. The polymer composition of microplastics are different among the water bodies. The highest proportion in the Southern Jiangsu Canal is polyethylene terephthalate, polycarbonate and polyethylene. The highest proportion of Suzhou Urban Area are polypropylene, chlorinated polyethylene and polycarbonate.The key factors affecting the distribution of microplastics in water at different scales were revealed. At the river basin scale, the concentration of microplastics in canal water is closely related to the socio-economic development level of cities along the river. The abundance of microplastics in the Southern Jiangsu Canal increased by 26% to 211% after flowing through the city. At the urban scale, the amount of river garbage and urban development level are positively correlated with the abundance of microplastics in water. The contribution of tourist areas, commercial areas, public land, residential areas and transportation land to microplastics decreases sequentially.It is found that there are obvious differences in the removal ability of different kinds of microplastics by different sewage treatment processes, and the interception law of microplastics by drainage network. The abundance of microplastics in the typical organized emission source, Suzhou urban sewage treatment plant effluent, ranges from 13.87 to 32.93 particles/L, reduced by 29.73% to 82.90% relative to the influent. Polypropylene has a high interception rate in the wastewater treatment plant. Plastic products used in wastewater treatment plants and drainage networks also contribute to the emission of microplastics.Fugitive emissions in cities are a major source of microplastics in water bodies. The abundance of microplastics in the typical fugitive emissions source, the silt of drainage pipes in Suzhou, ranges from 13.8 to 107.4 particles/g dry weight, with an average of 34.3 ± 29.3 particles/g dry weight. The type of dwelling, the intensity of water activities, the level of greening around the river, and the intensity of traffic were the potential urban factors affecting the fugitive emission of microplastics. The direct emission of polycarbonate and polyethylene terephthalate products is the main form of entering the water environment, and management in the process of its use and abandonment should be strengthened.
