纳米二氧化铈对蛋白核小球藻和大型溞的毒性及其在大型溞体内的形态转化

随着纳米技术的飞速发展,纳米材料的应用日益广泛。同时,这类具有独特物理化学特性的微小颗粒对环境和健康的影响引起了人们的关注。本工作参考国际经济合作与发展组织(OECD)化学品生态毒理测试方法,以蛋白核小球藻(Chlorella pyrenoidosa)和大型溞(Daphnia magna)为受试生物,研究了CeO_2纳米颗粒暴露对小球藻生长、叶绿素含量和细胞内活性氧水平以及大型溞运动能力的影响,分析了大型溞体内铈的形态。随着暴露浓度的升高和时间延长,CeO_2纳米颗粒逐渐抑制小球藻的生长,导致叶绿素水平的降低和活性氧水平升高。暴露96 h后,CeO_2纳米颗粒对小球藻生长的EC50为30.4 mg·L-1,而对大型溞活动抑制的24 h、48 h-EC50分别为430.2 mg·L-1和142.7 mg·L-1。根据中华人民共和国环境保护行业标准中的毒性分级标准,CeO_2纳米颗粒对小球藻属于中毒性物质,对大型溞属于低毒性物质。CeO_2纳米颗粒在大型溞体内主要以Ce(IV)的形式存在,约有3%转化为Ce(III)。对CeO_2纳米颗粒的水生态效应给予足够重视并深入研究其毒性作用机制。

Toxicity of CeO2 Nanoparticles to Chlorella pyrenoidosa and Daphnia magna, and Its Transformation inside the Daphnia magna

With the rapid development of nanotechnology, nanomaterials have been used in many applications. Meanwhile, the potential impacts of these tiny particles with unique physicochemical properties on the environment and human health have attracted increasing attention from the public. In accordance with the standard OECD Guidelines for the testing of chemicals (OECD 201 and 202), we studied the ecotoxicity of CeO2 nanoparticles (nCeO2) with the size of 6.44 nm to green algae (Chlorella pyrenoidosa) and water-flea (Daphnia magna). Effects of nCeO2 on the algal biomass, chlorophyll content, and cellular reactive oxygen species (ROS) level as well as daphnia acute immobilization were investigated. With the increase of exposure concentration and time, the growth of chlorella cell was gradually inhibited. The content of chlorophyll in the algae decreased, whereas the cellular ROS level increased under the stress of nCeO2. The 96 h EC50 of nCeO2 on the growth of Chlorella pyrenoidosa was 30.4 mg·L-1 and the 24 and 48 h-EC50 of nCeO2 on Daphnia magna were 430.2 and 142.7 mg·L-1, respectively. According to the grading standards of the People''s Republic of China on environmental protection industry, nCeO2 can be assumed to be of moderate and low toxicity for Chlorella pyrenoidosa and Daphnia magna, respectively. The majority of Ce in Daphnia magna was present as Ce(IV), while about 3% was transformed into Ce(III). Further research on the toxic mechanisms of nCeO2 is highly needed in order to minimize the adverse ecological effects.