Bioaccumulation effects of microplastics and heavy metals pollutants in the dominant freshwater fish species in the Longkou entry of Raohe River, Lake Poyang Basin

水体生态环境中的微塑料与重金属污染问题正日益受到热切关注.为探讨微塑料与重金属对水产品的复合生态效应，选择鄱阳湖-饶河段优势淡水鱼为研究对象，对鱼体内微塑料及重金属Cu、Cd、Pb、Zn、Cr等元素的生物累积作用进行分析与评价.结果表明：调查区域水环境中微塑料的丰度范围10~64 items/L，平均值38.56 items/L.8种淡水鱼消化道微塑料丰度范围为1.21~9.11 items/g，平均丰度为5.40 items/g；鳃部丰度范围0.61~5.00 items/g，平均丰度为2.87 items/g；微塑料类型主要有碎片类、纤维类、薄膜类和颗粒类4种，其聚合物成分主要为聚乙烯（PE）、低密度聚乙烯（LDPE）、聚丙烯（PP）和聚苯乙烯（PS）；颜色以透明及彩色为主；微塑料粒径范围为0.01~9.5 mm，粒径>0.5 mm的微塑料所占比例为79.07%，鱼体内与其生存水环境中微塑料的丰度特征（形态、粒径、颜色和聚合物类型组分比例）具有一定相似性.各鱼类对微塑料的累积系数（BAF）平均值为178.29，不同鱼类累积微塑料的能力大小次序为：乌鳢（Channa argus）、黄颡鱼（Pelteobagrus fulvidraco） > 鲦鱼（Hemicculter leuciclus）、草鱼（Ctenopharyngodon idellus）、鲶鱼（Silurus asotus） > 鲤鱼（Cyprinus carpio）、刀鱼（Coilia ectenes）、鲫鱼（Carassius auratus）.鱼体肌肉组织内重金属Cu、Cd、Pb、Zn、Cr的平均含量分别为4.27、0.13、0.28、11.73、0.53 mg/kg，均符合无公害水产品的要求且低于人体消费卫生标准，属于安全食用范围；鱼类对5种不同重金属的累积能力大小次序为Zn > Cu > Cd > Pb > Cr，不同鱼类对不同重金属的累积能力具有差异性.通过扫描电镜（SEM）与能谱分析（EDS）检测到各类型微塑料表面均有上述5种重金属元素，证实微塑料可能成为重金属的附着载体，相关性分析表明微塑料与Cu呈极显著相关，与Cd、Pb均呈显著相关；微塑料的存在一定程度上会增强Cu、Cd与Pb的累积效应，并可能产生复合污染效应.;Pollution of microplastics and heavy metals in aquatic eco-environment is attracting more and more attention. In the present study, in order to explore the bioaccumulation characteristics of microplastics and heavy metals in organisms, we selected eight dominant freshwater fish species in the Lake Poyang and Raohe River as the research materials. The concentrations of heavy metals (i.e. Cu, Cd, Pb, Zn and Cr) and microplastics in the fishes were measured and analyzed. The results indicated that the abundance of microplastics in water environment ranged from 10 to 64 items/L, with an average of 38.56 items/L. The abundance of microplastics in the digestive tract of the eight fish species ranged from 1.21 to 9.11 items/g, with an average of 5.40 items/g, while the abundance of microplastics in gills of fish varied between 0.61 and 5.00 items/g, with a mean of 2.87 items/g. There were four types of microplastics in fishes including debris, fibers, films and pellets. The polymer components were mainly polyethylene (PE), low-density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS) that were mainly transparent and colorful. The particle size of microplastics ranged from 0.01 to 9.50 mm, and 79.07% of the microplastics had particle size>0.5 mm. The abundance characteristics (i.e. types, particle size, color and polymer composition) of microplastics in fishes were similar as those in water environment. The averaged bioaccumulation coefficient of microplastics in fishes was 178.29. The bioaccumulation ability of microplastics in fishes was ordered as follows:Channa argus, Pelteobagrus fulvidraco > Hemicculter leuciclus, Ctenopharyngodon idellus, Silurus asotus > Cyprinus carpio, Coilia ectenes, Carassius auratus. The contents of heavy metals including Cu, Cd, Pb, Zn and Cr in the muscle tissues of fishes were 4.27 mg/kg, 0.13 mg/kg, 0.28 mg/kg, 11.73 mg/kg and 0.53 mg/kg, respectively, which meet the requirements of pollution-free aquatic products and are lower than the health standards for human consumption. The enrichment ability of the fishes to the five heavy metals was ordered as follows:Zn > Cu > Cd > Pb > Cr. Different fish species showed different ability on the accumulation of a specific type of heavy metals, which is closely related to their feeding habits. The five heavy metals were detected on the surface of various microplastics by using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) methods, suggesting that microplastics may be the attachment carrier of heavy metal pollutants. Correlation analyses showed that the concentration of microplastics in fishes were significantly correlated with that of Cu, Cd and Pb, probably because that the presence of microplastics enhances the cumulative effects of Cu, Cd and Pb, and lead to the compound pollution effects.