Toxic Effects Of Single And Combined Pollution Of Multi-Walled Carbon Nanotubes And Zinc Oxide Nanoparticles On Cabbage

The natural environment is a complex system,and not only one kind of nanomaterial can enter the environment.The nanomaterial entering the environment will not act alone,but will interact with other substances in the environment and jointly affect the ecological environment and other organisms.However,many studies only consider the phytotoxicity of one nanomaterial,and do not consider the effect of two or more nanomaterials on the phytotoxicity.When two nanomaterials coexist,they may produce antagonistic,synergistic and independent toxic effects in the environment,affecting the stability of the ecosystem.Multi-walled carbon nanotubes(MWCNTs)and zinc oxide nanoparticles(Zn O NPs)are two common and widely used nanomaterials in the water environment,which are introduced into the environmental system during production,use and transportation.Cabbage is a common vegetable that often appears in human daily life and is closely related to human diet.Besides,its breeding time is short and it has obvious traits,so it is selected as the model organism for this experiment.The effects of single toxicity of MWCNTs(0,1,10,50,100,200 mg/L)and Zn O NPs(0,1,10,50,100,200 mg/L)on cabbage seedlings were studied.By measuring root and stem length,chlorophyll a content and catalase(CAT)activity of plants,the toxic effects of single pollution of MWCNTs and Zn O NPs on cabbage were analyzed,and the concentration range of toxic effects of MWCNTs and Zn O NPs on cabbage seedlings was determined.Then the effects of the combined toxicity of MWCNTs(0,10,100 mg/L)and Zn O NPs(0,10,50,100 mg/L)on cabbage seedlings were investigated.The toxic effects of MWCNTs and Zn O NPs combined pollution on cabbage were studied by measuring root and stem length,chlorophyll content,oxidative stress,antioxidant enzyme activity,metal element content and root scanning electron microscopy.The toxicity of single MWCNTs to cabbage was attributed to direct oxidative damage,while the toxicity of single Zn O NPs to cabbage was attributed to Zn O NPs and dissolved high concentration of zinc ions.In addition,Zn O NPs(10 mg/L)improved the toxicity of MWCNTs to cabbage by increasing the activity of antioxidant enzymes.Due to the high zinc content,Zn O NPs(50 and 100 mg/L)upset the balance of other metals in plants and increased the toxicity of MWCNTs.In conclusion,the combined toxicity of different concentrations and types of nanomaterials should be considered in order to assess environmental risks more accurately.