纳米银在水生态食物链中的迁移和生物放大

Silver nanoparticles (AgNPs) are emerging as one of the fastest growing products and the most widely used nanomaterials in the world. As the result, the potential hazards of AgNPs on the ecological environment is anticipated. Current research on the ecological impacts of silver nanoparticle has focused on the toxic effects at both biological individual level and cell level. Little is known about the biomagnifications and trophic transfer of AgNPs in freshwater food chain, despite the fact that the trophic transfer in freshwater food chain is considered to be a major pathway for AgNPs introduction into the environment. To begin addressing this knowledge gap, we will construct a simple freshwater food chain using the model organisms (Daphnia magna) and zebrafish（Danio rerio）to investigate the potential biomagnifications and trophic transfer of AgNPs. Two possible pathway of AgNPs transport in aquatic ecosystems including direct water column transport and food chain transfer will be investigated, and a group of ecology related indexes such as Bio-accumulation factor (BAF), Bio-magnification factor (BMF) will be measured to disclose the law of biomagnifications and cumulative effects of AgNPs in aquatic organisms, as well as their migration pathway in the simple freshwater food chain. Our study is expected to present the first evidence of trophic transfer of AgNPs from a primary consumer (D. magna) to a secondary consumer (Danio rerio) as well as the first evidence of biomagnifications of AgNPs within a simple freshwater food chain. These results have important theoretical values for elucidating the mechanisms of eco-toxicity and environmental behavior of the nano-materials which has been considered as a new type of potential contaminants effectors. Our results also have important implications for potential ecological risks assessment on other types of nanomaterials.

银纳米是世界上产量最大、应用最广的纳米材料，其大量排放将对生态环境构成巨大的潜在威胁。目前对纳米银的生物安全研究多集中在生物个体和细胞水平的毒性效应评估，缺乏对纳米银在生态食物链中迁移行为和生物放大等生态效应的认识。本项目拟以"水蚤-斑马鱼"为简单水生态食物链模型，通过考察水体暴露和食物链传递两条途径分别对纳米银在水蚤和斑马鱼体内各自的积累和迁移情况，分析其在水生态食物链中的生物积累指数（BAF）和生物放大指数（BMF），探讨纳米银在食物链中的迁移行为和积累过程，揭示纳米银在水生态食物链中的积累效应、迁移行为和生物放大效应规律。通过本研究，可判识纳米银在水生态食物链中的生物放大效应，阐明其在食物链中的积累和迁移机制，对揭示纳米银这类潜在新型污染物的环境行为和生态毒性效应机制具有重要理论价值，也可为其它纳米材料生态安全评估提供科学依据。

纳米银是世界上产量最大、应用最广的纳米材料，其大量排放将对生态环境构成巨大潜在危害。目前关于纳米银的生态环境效应研究大多集中于对单个生物的毒性效应评估，缺乏对纳米银在生态食物链中的迁移、积累和生物放大等生态效应的认识。本项目（1）以“水蚤-斑马鱼”为简单的水生态食物链模型，探明了纳米银通过水体暴露和食物链传统两条途径在斑马鱼体内的迁移和积累情况，分析了纳米银在水生态食物链中积累、传递和生物放大效应。结果表明，当暴露浓度为100 μg/L和10 μg/L时，粒径为50 nm的纳米银在水生态食物链“水蚤-斑马鱼”中的生物积累指数（BCF）分别为0.015和0.012，生物放大指数(BMF)分别为0.023和0.014。这一结果证实了纳米银在这一简单水生态食物链中的转移效率较低，无明显的生物放大效应。（2）合成和表征了粒径分别为15 nm、50 nm和100 nm的三种纳米银颗粒，以鱼类红血细胞为细胞模型，阐明了粒径介导的纳米银颗粒对细胞的毒性效应和内在化机制。结果表明，纳米银在红血细胞表面的吸附和内在化均受其粒径影响，中等粒径的纳米银（50 nm）具有最高的内在化率；小粒径的纳米银（15 nm）则具有最强的生物毒性效应，导致最强烈的红细胞溶血、细胞膜损伤、脂质过氧化以及抗过氧化物酶活性产物增加，而这些毒性效应均是源于纳米银颗粒与红血球直接相互作用导致。本项目的研究成果对于揭示纳米银在水生态食物链中的积累、传递和生物放大效应具有重要科学价值，也可为阐明纳米银的生态毒性效应机制提供重要参考。