天然有机质对TiO_(2)纳米颗粒与PCB-77藻类毒性影响及致毒机理  

Effect and Mechanism of Natural Organic Matter on Toxicity of TiO_(2) Nanoparticles and PCB-77 to Algae

作　　者：李青 张帅[1,2] 王济 Li Qing;Zhang Shuai;Wang Ji(College of Geography and Environmental Science,Guizhou Normal University,Guiyang 550025,China;State Key Laboratory Breeding Base for Karst Mountain Eco-environment of Guizhou Province,Guiyang 550025,China)

机构地区：[1]贵州师范大学地理与环境科学学院,贵阳550025 [2]贵州省喀斯特山地生态环境国家重点实验室培育基地,贵阳550025

出　　处：《生态毒理学报》2021年第6期244-255,共12页Asian Journal of Ecotoxicology

基　　金：国家自然科学基金资助项目(41807336);贵州省科技计划项目(黔科合基础[2020]1Y189;黔科合LH字[2017]7345号;黔科合平台人才[2018]576919);贵州师范大学2016年博士科研启动项目;贵州省世界一流学科建设计划项目:喀斯特生态环境学科(黔教科研发[2019]125号);学术学位授权点-环境科学与工程(硕)(0418001)。

摘　　要：为探究天然有机质(natural organic matter,NOM)对纳米二氧化钛(TiO_(2))与3,3’,4,4’-四氯联苯(3,3’,4,4’-tetrachlorobiphenyl,PCB-77)藻类毒性影响及致毒机理,以小球藻为实验受试生物,测定了纳米TiO_(2)与PCB-77单独及复合暴露在NOM存在与不存在条件下对小球藻生长、细胞形态、活性氧(reactive oxygen species,ROS)和丙二醛(malondialdehyde,MDA)含量及超氧化物歧化酶(superoxide dismutase,SOD)和过氧化氢酶(catalase,CAT)活性的影响。结果表明,所有暴露组均对小球藻的生长有一定的抑制作用。团聚沉降实验结果说明,纳米TiO_(2)在水环境中易团聚,PCB-77和NOM通过影响纳米TiO_(2)团聚进而影响小球藻的生长,这些团聚体附着在藻细胞表面,导致细胞间相互遮蔽,影响藻细胞光合作用和细胞呼吸,进而影响藻细胞生长,与实时定量PCR检测基因的结果一致。用透射电子显微镜(transmission electron microscope,TEM)观察发现,纳米TiO_(2)单独暴露与PCB-77复合暴露在NOM存在与不存在条件下,藻细胞周围附着纳米TiO_(2),有一部分进入藻细胞内部,使细胞膜破损、质壁分离、细胞器结构不清晰以及出现电子致密体和空泡结构,小球藻细胞形态遭到损坏,这是直接接触造成的物理损伤。通过测定藻细胞内ROS和MDA含量可知,暴露在纳米TiO_(2)中产生ROS含量最高,所受的氧化损伤最大,氧化胁迫是纳米TiO_(2)致毒机理之一。因此,NOM对纳米TiO_(2)与PCB-77藻类致毒机理的影响归纳为吸附团聚作用所造成的遮蔽效应、直接接触的物理损伤和产生大量ROS造成的氧化损伤。In order to explore the effect of natural organic matter(NOM)on algae toxicity induced by nano-TiO_(2)and PCB-77 and its toxic mechanism,Chlorella vulgaris was used as the experimental organism.The effects of both presence and absence of NOM on the growth,cell morphology,contents of reactive oxygen species(ROS)and malondialdehyde(MDA),activities of superoxide dismutase(SOD)and catalase(CAT)of Chlorella vulgaris were determined.The results showed that the growth of Chlorella vulgaris was inhibited in all exposure groups.The agglomeration and sedimentation experiments showed that nano-TiO_(2)was easy to agglomerate in water environment.PCB-77 and NOM affected the growth of Chlorella vulgaris by affecting the agglomeration of nano-TiO_(2).These aggregates attachment to the surface of algae cells,resulting in mutual shielding between cells,which affecting the photosynthesis and cell respiration of algae cells,and eventually the growth of algae cells.This was therefore consistent with the results of real-time quantitative PCR.Transmission electron microscope observation showed that when nano-TiO_(2)and PCB-77 were exposed alone or in combination with NOM,nano-TiO_(2)adhered around the algal cells,some of which entered into the algal cells,causing cell membrane damage and plasmolysis,unclear organelle structure,electron dense body and vacuole structure,and thus damaged morphology of Chlorella vulgaris cells.All of which were the physical damages caused by direct contact.By measuring the content of ROS and MDA in algae cells,it can be seen that the exposure of the nano-TiO_(2)lead to the highest content of ROS and the severest damage of the cells.Oxidative stress is one of the toxic mechanisms of nano-TiO_(2).Therefore,the toxic mechanism of nano-TiO_(2)and PCB-77 on algae with NOM can be summarized as follows:shielding effect caused by adsorption agglomeration,physical damage caused by direct contact and oxidation damage caused by excessive amount of ROS.

关 键 词：纳米TiO_(2) 天然有机质 PCB-77 小球藻 毒性效应 致毒机理 

分 类 号：X171.5[环境科学与工程—环境科学]