纳米二氧化钛与砷在藻-大型蚤食物链中的相互作用机制

Nanotechnology is advancing rapidly and could soon become a trillion-dollar industry. Subsequently, release of substantial amount of engineered nanoparticles (ENPs) into the environment is inevitable. Understanding the safety, environmental and human health implications of nanotechnology-based products is of worldwide importance. Titanium dioxide nanoparticles (nano-TiO2) have attracted considerable attention because of their unique properties and widespread uses in suncreens, toothpastes, surface coatings, and water treatments. Currently, researches on the risk of nano-TiO2 are one of the critical topics about the health and safety of nanomaterials, and also are urgently significant issues during the scientific development of nanotechnology in our country and other worlds. However, little information, so far, is available for the interaction of nano-TiO2 with other pollutants in food chains. As a result, it is extremely unclear that the effects of the interaction on the bioavailability, bioaccumulation and transfer of other pollutants and its related mechanisms. The lack of this special researches needs to be make up due to the potential risk of nano-TiO2 in aquatic environment. Algae-dephnia is one of important food chains in aquatic environment, in which researches on the uptake, bioaccumulation and transfer of arsenic possess pivotal therotic roles and practical values. The main objectives of this proposal are to (1) identify the responses of algae and daphnia under the interaction of nano-TiO2 and arsenic; (2) determine the changes of the arsennic and nano-TiO2 amount, arsenic speciation under this interaction; (3) verify the effects of this interaction on the bioaccumulation dynamics in algae-daphnia food chain; (4) reveal the mechanisms of the interaction of nano-TiO2 and arsenic in algae-daphnia food chain. The proposed project will provide insights into the impacts of engineered nano-TiO2 on other pollutants behavior in food chain and the environmental risk of engineered nanomaterials, and will improve accuracy and relevancy of the weight-of-evidence of decision-making process for engineered nanomaterials management.

纳米TiO2的风险研究是当前纳米材料健康与安全新兴研究的热点之一，也是目前国家纳米科技科学发展亟待解决的重要科学问题。迄今纳米TiO2与其它污染物在食物链中的相互作用研究极近空白，缺乏了解二者互作时如何影响污染物的生物有效性、累积和传递的作用机制。藻-大型蚤作为水生态系统的重要组成部分，砷在该食物链中的吸收累积及转化研究具有重要理论作用和实际价值。本项目围绕纳米材料与其它污染物相互作用的重要科学问题，多学科交叉，拟系统研究纳米TiO2与砷互作时藻、大型蚤的胁迫响应、藻-大型蚤食物链中砷、纳米TiO2含量、砷形态等变异特性，探明纳米TiO2对藻-大型蚤食物链中砷累积动力学的影响规律，查清纳米TiO2与砷互作时对藻和大型蚤的胁迫作用，揭示纳米TiO2与砷在藻-大型蚤食物链中的相互作用机制，促进对纳米TiO2与其它污染物相互作用规律的理解，提升纳米材料在环境中的健康与风险的认识。

纳米TiO2的风险研究是当前纳米材料健康与安全新兴研究的热点之一，也是目前国家纳米科技科学发展亟待解决的重要科学问题。本项目围绕纳米材料与其它污染物相互作用的重要科学问题，系统研究纳米TiO2与砷互作时藻、大型蚤的胁迫响应、藻-大型蚤食物链中砷、纳米TiO2含量、砷形态等变异特性，探明了纳米TiO2对藻-大型蚤食物链中砷累积动力学的影响规律，查清了纳米TiO2与砷互作时对藻和大型蚤的胁迫作用，揭示了纳米TiO2与砷在藻-大型蚤食物链中的相互作用机制，促进对纳米TiO2与其它污染物相互作用规律的理解，提升了纳米材料在环境中的健康与风险的认识。主要结论如下：.TEM图像证明纳米二氧化钛可以进入暴露的藻体。因而，纳米二氧化钛作为载体促进了这两种藻体的累积与甲基化，但其累积与甲基化因砷的不同形态与不同藻类而异。其中，纳米二氧化钛显著提高了五价砷在铜绿微囊藻以及三价砷在斜生栅藻的累积。同时，铜绿微囊藻的砷甲基化在2 mg/L的纳米二氧化钛处理以及斜生栅藻的五价砷处理中比较高。另外，斜生栅藻表现出较高的砷甲基化。砷在藻细胞中从纳米二氧化钛解离下来增加了藻体的氧化压力，从而促进了藻体砷的甲基化。.同时，低浓度TiO2 NPs降低了AsV对大型蚤的毒性，而高浓度TiO2 NPs增强了AsV对大型蚤的毒性；相比较，nTiO2却减小了As（Ⅲ）对大型蚤的毒性。TiO2 NPs充当了AsV的载体，TiO2 NPs能显著提高大型蚤内As的含量。As和TiO2 NPs主要集中在大型蚤的肠道内，且As和TiO2 NPs在大型蚤内的分布具有显著相关性（P < 0.01）。As和TiO2 NPs的亚细胞分布具有很大差异（P < 0.05），说明由TiO2 NPs通过吸附作用携带进入大型蚤体内的As在大型蚤体内与TiO2 NPs发生了解离。作为大型蚤食物的斜生栅藻也增加了As和TiO2 NPs在大型蚤体内的累积，说明绿藻充当了TiO2 NPs和AsV的有效载体。添加食物后，金属敏感相中的TAs含量高于空白对照组，而TiO2 NPs依旧主要分布在生物解毒相中，说明食物存在时TiO2 NPs和AsV在大型蚤体内发生了解离。即金属敏感相中的TAs主要为iAs，说明食物的存在可能会增加AsV毒性。