鄱阳湖流域水葫芦(Eichhornia crassipes)对水体微塑料的吸附截留效应

微塑料是环境中的新型污染物，随着人们对微塑料污染的认识，微塑料在河流和湖泊等淡水湿地环境中的迁移问题受到普遍关注.中国内陆最大淡水湖鄱阳湖湿地受五河流域及其地表径流的影响，湿地水环境中的微塑料污染问题也不容忽视.为了解鄱阳湖各流域水体中微塑料的分布现状及水生植物对微塑料的吸附截留效应，选择鄱阳湖流域的赣江、信江、抚河、修水和饶河这五河水系入湖段为研究区，以各流域水体及其普遍存在的漂浮植物水葫芦（Eichhornia crassipes）为研究对象，分析鄱阳湖五河流域水葫芦对水体微塑料的吸附截留特征，探讨水生植物对水体环境中的微塑料是否具有吸附或截留效应，阐明水葫芦对微塑料的吸附与水体赋存微塑料的相关性，解析微塑料在湿地环境中的迁移特性，为鄱阳湖湿地环境中微塑料的管控及污染治理提供一定的理论基础与依据.在鄱阳湖流域赣江、抚河、信江、饶河和修水的五河水系入湖区和湖口出湖区共设置18个采样点，分别采集水表漂浮的水葫芦整株样品和水深约1 m处的水样，采用HNO₃（65%）-H₂ O₂（30%）混合试剂消解水样后抽滤分离水体及水葫芦体表微塑料；采用显微鉴定方法观察微塑料的颜色、粒径和形态等特征，采用Nano Measurer 1.2软件统计各流域水体和水葫芦体表中分离出的微塑料丰度；采用傅立叶变换红外（FTIR）光谱仪鉴定不同形态微塑料的聚合物成分.鄱阳湖流域各水体微塑料丰度处于中度偏高水平，丰度范围为65.5~353 n ·L^-1，且以0~0.5 mm范围内的小粒径微塑料为主，占各流域水体中微塑料的80%以上；各流域水葫芦截留或吸附的微塑料丰度范围为36~204 n ·kg^-1，且以0~1.5 mm范围内的小粒径微塑料为主，所占比例达80%以上；水葫芦吸附0~0.5 mm粒径范围内的微塑料丰度含量与水体中0~0.5 mm粒径范围内的微塑料丰度间呈显著相关，水葫芦对水体中占比较高的小粒径微塑料具有明显的吸附效应.鄱阳湖五河流域水体微塑料的聚合物成分以聚乙烯和聚苯乙烯为主体；各流域水体微塑料的丰度处于较高水平，以0~0.5 mm的小粒径微塑料为主，对水体生物及水环境易构成生态风险.各流域水葫芦对水体微塑料具有显著的吸附效应，且以吸附0~1.5 mm的小粒径微塑料为主；水葫芦吸附0~0.5 mm粒径范围内的微塑料丰度值与水体中0~0.5 mm粒径范围内的微塑料丰度间存在显著相关性；水葫芦对水体中的小粒径微塑料具有较强的吸附效应，可为水生植物吸附或截留水体环境中的微塑料提供一定的参考依据.

Adsorption and Interception Effects of Eichhornia crassipes on Microplastics in Water of the Poyang Lake Basin

Microplastics are novel pollutants in the environment, and with the awareness of microplastic pollution, the migration of microplastics in freshwater wetland environments such as rivers and lakes has received widespread attention. The wetland of Poyang Lake, the largest inland freshwater lake in China, is influenced by the five river basins and their surface runoff, and the microplastic pollution in the wetland water environment cannot be ignored. In order to understand the occurrence of microplastics in the water bodies of Poyang Lake and the adsorption and interception effects of aquatic plants on microplastics, five river basins of Poyang Lake, including the Ganjiang River, Xinjiang River, Fuhe River, Xiushui River, and Raohe River, were selected as the study area, and the water samples of each basin and the prevalent floating plant Eichhornia crassipes were used as the research objects to study the adsorption and interception characteristics of microplastics in the water of the Poyang Lake basin. The study investigated the adsorption and interception characteristics of E. crassipes on microplastics in water bodies, explored whether the aquatic plants had adsorption or interception effects on microplastics in the water bodies, clarified the correlation between the adsorption of microplastics by E. crassipes and microplastics in the water bodies, analyzed the migration characteristics of microplastics in the wetland environment, and provided a theoretical basis for the control and pollution management of microplastics in the wetland environment of the Poyang Lake basin. A total of 18 sampling points were set up in the main entry areas of the Ganjiang River, Fuhe River, Xinjiang River, Raohe River, and Xiushui River, and the exit of the lake into the Yangtze River confluence area in the Poyang Lake basin, and water samples were collected from the all the E. crassipes floating on the water surface and water at a depth of approximately 1 m. Microplastics were separated from water samples and the plant surface at the root zone of E. crassipes by filtration; after the water samples were disintegrated with an HNO₃ (65%)-H₂O₂ (30%) reagent mixture, the microscopic identification method was used. The microplastics were characterized by color, particle size, and morphology, and the abundance of microplastics in the water and E. crassipes root zone was calculated using Nano Measurer 1.2 software, and the polymer composition of different forms of microplastics was identified via Fourier transform infrared (FTIR) spectroscopy. The abundance of microplastics in the water samples of the Poyang Lake basin was moderately high, ranging from 65.5 to 353 n·L^-1, and the small-sized microplastics in the range of 0-0.5 mm mainly accounted for more than 80% of the microplastics in the water samples of the basin. The abundance of microplastics retained or adsorbed by E. crassipes in the basin ranged from 36 to 204 n·kg^-1, and the small-sized microplastics in the range of 0-1.5 mm mainly accounted for more than 80% of the microplastics in the water bodies of the basin. The abundance of microplastics retained or adsorbed by E. crassipes in different watersheds ranged from 36 to 204 n·kg^-1, and the proportion of small-sized microplastics in the range of 0-1.5 mm was more than 80%. The abundance of microplastics in the particle size range of 0-0.5 mm adsorbed by E. crassipes was significantly correlated with the abundance of microplastics in the particle size range of 0-0.5 mm in the water bodies. The effect of E. crassipes on microplastics in the water column was significant. The polymer composition of microplastics in the water samples of the five river basins of Poyang Lake included mainly polyethylene and polystyrene, the abundance of microplastics in the water samples of the Poyang Lake basin was at a high level, and the main microplastics were of small particle size in the range of 0-1.5 mm, which easily pose ecological risks to the water body organisms and water environment. The abundance of microplastics in the range of 0-0.5 mm particle size was significantly correlated with the abundance of microplastics in the range of 0-0.5 mm particle size in the water body. Eichhornia crassipes also had a strong adsorption effect on microplastics in the water body, which can be used by aquatic plants to adsorb or retain microplastics in the water body. The strong adsorption effect of E. crassipes on microplastics in the water column can provide a reference for the adsorption or retention of microplastics in the water column.