不同粒径聚苯乙烯微塑料单独与联合暴露在斑马鱼体内的生物累积

Bioaccumulation of different size polystyrene microplastics in zebrafish with single and combined exposure

目的 研究不同粒径聚苯乙烯微塑料颗粒(PS-MPs)的单独与联合暴露在斑马鱼体内的生物累积特征。方法 将240尾斑马鱼随机分50 nm(红)组、500 nm(红)组、5 000 nm(红)组、500 nm(绿)组和5 000 nm(绿)组,联合暴露的50 nm(红)+500 nm(绿)组、50 nm(红)+5 000 nm(绿)组和500 nm(红)+5 000 nm(绿)组,分别予剂量为10 mg/L的相应粒径和荧光颜色的PS-MPs进行暴露实验。在持续暴露后6、24、48、72、96和120 h时间点,采用荧光显微镜观察斑马鱼体内的荧光强度,将其标准化后进行比较。结果 (1)单独暴露。50 nm(红)组、500 nm(红)组和5 000 nm(红)组斑马鱼体内6个时间点红色荧光PS-MPs的标准化荧光强度均依次下降(P值均<0.05);3组斑马鱼体内PS-MPs标准化荧光强度均随着暴露时间的延长而增加(P值均<0.01)。(2)联合暴露。与同时间点50 nm(红)组比较,50 nm(红)+500 nm(绿)组、50 nm(红)+5 000 nm(绿)组斑马鱼体内6个时间点50 nm红色荧光PS-MPs的标准化荧光强度均下降(P值均<0.05)。与同时间点500 nm(绿)组比较,50 nm(红)+500 nm(绿)组的48、72、96、120 h时间点斑马鱼体内500 nm绿色荧光PS-MPs的标准化荧光强度均升高(P值均<0.05),500 nm(红)+5 000 nm(绿)组的6个时间点斑马鱼体内500 nm红色荧光PS-MPs的标准化荧光强度均升高(P值均<0.05)。与同时间点5 000 nm(绿)组比较,50 nm(红)+5 000 nm(绿)组6、48、72、96、120 h时间点斑马鱼体内5 000 nm绿色荧光PS-MPs的标准化荧光强度均升高(P值均<0.05),500 nm(红)+5 000 nm(绿)组6个时间点斑马鱼体内5 000 nm绿色荧光PS-MPs的标准化荧光强度均升高(P值均<0.05)。各联合暴露组PS-MPs的相应标准化荧光强度均随着暴露时间的延长而增加(P值均<0.01)。结论 PS-MPs单独暴露在斑马鱼体内的累积分布具有粒径-效应特征;PS-MPs单独与联合暴露在斑马鱼体内的累积分布均具有时间-效应特征;联合暴露下,纳米级PS-MPs在斑马鱼体内的累积减少,亚微米级和微米级PS-MPs在斑马鱼体内的累积增加。

Objective To investigate the bioaccumulation of different size polystyrene microplastics(PS-MPs) in zebrafish with single and combined exposure. Methods A total of 240 zebrafish were randomly divided into single-exposure group, which exposed to 50 nm(red), 500 nm(red), 5 000 nm(red), 500 nm(green), 5 000 nm(green) PS-MPs, and co-exposure group, which exposed to 50 nm(red) + 500 nm(green), 50 nm(red) + 5 000 nm(green) and 500 nm(red) + 5 000 nm(green) PS-MPs. The zebrafish were exposed to 10 mg/L PS-MPs with corresponding sizes and color. After exposure to PS-MPs for 6, 24, 48, 72, 96, and 120 hours, the zebrafish were observed under a fluorescence microscope at each time point. Then, the PS-MPs′ fluorescence intensity in zebrafish in each group was standardized and analyzed. Results i) Single-exposure. As the particle sizes increased, the standardized fluorescence intensity of red PS-MPs in zebrafish decreased at all the 6 time points(all P<0.05). The standardized fluorescence intensity of different size red PS-MPs in zebrafish increased with the extension of exposure time in the 50 nm(red), 500 nm(red) and 5 000 nm(red) groups(all P<0.01). ii) Combined exposure. The standardized fluorescence intensity of the 50 nm(red) PS-MPs in the 50 nm(red) + 500 nm(green) and 50 nm(red) + 5 000 nm(green) PS-MPs group decreased at all the six time points(all P<0.05) compared with the 50 nm(red) group. The standardized fluorescence intensity of the 500 nm(green) PS-MPs in zebrafish in the 50 nm(red) + 500 nm(green) group increased at 48, 72, 96 and 120 hours(all P<0.05), while the standardized fluorescence intensity of the 500 nm(red) PS-MPs in zebrafish increased in the 500 nm(red)+5 000 nm(green) group at all the six time points(all P<0.05), compared with the 500 nm(green) group. The standardized fluorescence intensity of the 5 000 nm(green) PS-MPs in zebrafish increased in the 50 nm(red)+5 000 nm(green) group at 6, 48, 72, 96 and 120 hours(all P<0.05), and the standardized fluorescence intensity of the 5 000 nm(green) PS-MPs′ in zebrafish increased in the 500 nm(red)+5 000 nm(green) group at all the six time points(all P<0.05), compared with the 5 000 nm(green) group. The standardized fluorescence intensity of the corresponding PS-MPs in zebrafish in each co-exposure group increased with the extension of exposure time(all P<0.01). Conclusion The bioaccumulation of PS-MPs in zebrafish with single-exposure shows size-dependent manner. The bioaccumulation of PS-MPs in zebrafish with single-and combined-exposure shows time-dependent manner. Under combined exposure condition, the accumulation of nanoscale PS-MPs in zebrafish decreased, while the accumulation of submicron and micron PS-MPs increased in zebrafish.