纳米银(AgNPs)在喀斯特水生碎屑食物链的迁移行为和生态毒理效应

Silver nanoparticles (AgNPs) have attracted considerable attention because of their unique antimicrobial activities and widespread uses in consumer products. And most previous studies on the health risks and environmental impacts of AgNPs have focused on the biological effects and toxicities at individual level and cellular level, or the transfer of AgNPs from living plant organic matter across trophic levels. However, trophic transfer and ecotoxicological effects of AgNPs in detritus-based stream food chain have remained poorly understood despite detritus, or dead organic matter, a common feature of most ecosystems playing a frequently overlooked role as a dynamic heterogeneous resource and habitat for many species. Based on the leaf litter decomposition of Pterocarya stenoptera in streams of Karst region, a simplified model of detritus-based stream food chain consisting of microbially-colonized leaves, a primary consumer (the gammarid Gammarus lacustris), and a secondary vertebrate consumer (the fish Rhinogobius duospilus) was established. Then, the effect of hydrochemistry-linked toxicological mechanism of AgNPs on aquatic hyphomycetes was analyzed by investigating the effects on the community structure, biomass and extracellular enzyme activity of aquatic hyphomycetes. And the bioaccumulation and trophic transfer of AgNPs in both G. lacustris and R. duospilus were also analyzed by investigating the effects on the accumulation, release and transfer of AgNPs in these animals by exposuring to AgNPs-contaminated water and/or AgNPs-contaminated food transferring from detritus-based stream food chain. The research results will demonstrate the influence of hydrochemistry-linked toxicological mechanism of AgNPs on aquatic hyphomycetes associated leaf litter decomposition, the bioaccumulation and trophic transfer of AgNPs in detritus-based stream food chain. The results has important theoretical value for revealing the environmental behavior and toxicity mechanism of emerging pollutant such as AgNPs, and has important implications for risks associated with nanotechnology, including the potential for human exposure.

纳米银(AgNPs)在生态环境中的迁移、积累及毒性效应是目前研究的热点，但多集中在生物个体和细胞水平的毒性效应评估，或在以活植物为起点的食物链中的积累和迁移，而缺乏对其在碎屑食物链中生态效应的认识。本项目拟以喀斯特地区河流特征为背景，以“枫杨叶/水生真菌-湖泊钩虾-溪吻鰕虎鱼” 为水生态碎屑食物链模型，通过考察喀斯特地区水化学性质对AgNPs毒性水生真菌群落结构和代谢活动的影响以及水体暴露和碎屑食物链传递两条途径分别对AgNPs在湖泊钩虾和溪吻鰕虎鱼体内的积累、消除和迁移情况，分析AgNPs对水生真菌的毒理效应及其在碎屑食物链中的生物积累和迁移过程，揭示喀斯特地区水化学性质对AgNPs毒性水生真菌的机制和AgNPs在水生态碎屑食物链中的积累效应和迁移规律。本研究对揭示AgNPs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(AgNPs)在生态环境中的迁移、积累及毒性效应是目前研究的热点，但多集中在生物个体和细胞水平的毒性效应评估，或在以活植物为起点的捕食食物链中的积累和迁移，而缺乏其在碎屑食物链中的积累和迁移等生态效应的认识。本项目以喀斯特地区河流特征为背景，构建了以“枫杨叶/微生物（真菌和细菌）-米虾-溪吻鰕虎鱼” 为水生态碎屑食物链模型，深入研究了AgNPs在喀斯特河水中的表征及其在该碎屑食物链的积累、消除和迁移。首先研究了自然光和夜间人造光污染（ALAN）条件下，AgNPs在实验水体中表征，发现ALAN可通过改变系统中AgNPs的粒径和电位来调节其毒理效应；进而深入探究了AgNPs和河流常见微量元素污染物（Cd, As, Pb）对凋落物降解及其相关的微生物群落结构与功能的影响，发现ALAN不仅可以改变AgNPs和凋落物的特性，而且还可以通过改变凋落物降解相关的微生物群落结构与功能来减轻AgNPs对凋落物降解的负面影响；对As、Cd和Pb的研究也得到了类似结果，但与AgNPs的毒理效应机制不同。在此基础上，深入探究了AgNPs在碎屑食物链的生物有效性和动态迁移行为，发现AgNPs直接暴露对米虾96 h LC50远低于溪吻鰕虎鱼，而米虾和溪吻鰕虎鱼体内的Ag积累量均随着AgNPs暴露浓度的增加而增加，损伤程度则随研究部位的不同而发生较大变化。经碎屑食物链传递后，AgNPs在溪吻鰕虎鱼体类不同器官之间的积累发生较大变化：水体直接暴露表现为肝 >腮 > 肠 > 肌肉，而经食物链传递后则表现为肠 > 肝 > 腮 > 肌肉；组织病理学结果显示，AgNPs直接暴露对溪吻鰕虎鱼的肝组织和腮组织造成的损伤比经食物链传递严重。这些研究结果表明，AgNPs水生态毒理效应不仅受环境因素变化而变化，而且还与暴露浓度和方式有关。该结果也显示了以“枫杨叶/微生物群落-米虾-溪吻鰕虎鱼”为水生态碎屑食物链模型评估纳米材料毒理学效应的可行性。这些发现强调了在评估纳米材料对淡水生物和生态系统过程的潜在风险时考虑环境参数的重要性，为其它纳米材料生态安全评估提供科学依据和新视野。