The Toxicity Of Copper Oxide Nanoparticles On Wheat And Its Regulation Research

As a typical representative of nanomaterials,copper oxides nanoparticles（Cu O NPs）are favored in agricultural pest control,fertilizer,corrosion prevention and other aspects,but excessive use will cause different degrees of pollution to the soil.The concentration of Cu O NPs in environment is generally low,however,once absorbed by organisms,Cu O NPs can be continuously accumulated in specific tissues or organs,resulting in toxic effects.Soil amendments,such as crop straw and straw-derived biochar,have been widely used for remediation of soil pollution due to their convenience and cost-effectiveness.Therefore,two typical farmland soils in China were selected to conduct wheat root elongation experiment and pot experiment to explore the toxicity of Cu O NPs to wheat and the regulatory effects of straw and straw-derived biochar.The main research contents and results were as follows:（1）Using wheat root elongation as the evaluation endpoint,the toxicity effective concentration of Cu O NPs on wheat was determined from the dose effect curve for Guangdong（GD）red earths and Shandong（SD）fluvo-aquic soils with different physicochemical properties,and the toxicity of Cu O NPs was compared with those of Cu²⁺and copper oxide bulk particles（Cu O BPs）.The results showed that the toxicity of three different forms of copper to wheat follows the order of Cu²⁺>Cu O NPs>Cu O BPs,and the toxicity in GD red earth was greater than that in SD fluvo-aquic soil.In GD red earth,the 10%(EC₁₀),20%(EC₂₀),and 50%(EC₅₀)inhibition effect concentration of Cu O NPs were 250 mg·kg^-1,408 mg·kg^-1,and 945 mg·kg^-1,respectively,based on wheat root elongation,while those values in SD fluvo-aquic soil were364 mg·kg^-1,1020 mg·kg^-1,and 5933 mg·kg^-1,respectively.The content of DTPA-Cu in the soil spiked with three forms of copper was positively correlated with the concentration of added copper,and negatively correlated with wheat root length.（2）According to the results of wheat root elongation experiment,appropriate addition concentrations of Cu O NPs were determined to conduct wheat pot experiment.The toxicity effect and mechanism of Cu O NPs were explored using the ultrastructural damage in root and leaf as well as physiological and biochemical indicators of wheat seedlings as the evaluation endpoints.The results showed that the toxicity of Cu O NPs to wheat seedlings was greater in GD red earth than that in SD fluvo-aquic soil.Scanning electron microscopy images showed that Cu O NPs caused different degrees of damage to the root morphology of wheat,and the transmission electron microscopy images showed that Cu O NPs could enter the wheat leaf cells and cause damage to the ultrastructure of wheat leaves.Cu O NP stress decreased the chlorophyll content of wheat leaves,increased the antioxidant enzyme activity and membrane lipid peroxidation level of leaves.In addition,the addition of Cu O NPs also changed the accumulation of nutrient elements in wheats,with reduced contents of Zn and Fe in leaves and increased contents of Mg and Mn.（3）The toxicity regulation effect of soil amendments on wheat was studied by adding 2%,5%corn straw（CS）and biochar（CB）to Cu O NP contaminated soil.The results showed that the prepared straw and biochar contained functional groups such as–OH,C–H,–COOH and C–O.After soil improvement,the contents of TOC,total N,available P,available K,and available CEC all increased in varying degrees.The application of 2%and 5%of CS and CB in GD red earth increased wheat biomass and promoted root growth,and increased the content of chlorophyll in wheat leaves.The application of 2%and 5%of CS in SD fluvo-aquic soil had no significant effect on wheat biomass and root growth,but reduced the content of chlorophyll in wheat leaves.In addition,the application of 2%,5%of CS and CB reduced wheat antioxidant enzymes activity and the degree of membrane lipid peroxidation in both soils.The application of straw and biochar affected the transport of nutrient elements in wheat.The application of 2%,5%of CS and CB decreased the TF of Cu in GD red earth,while increased the TF of Cu in SD fluvo-aquic soil.The improvement effect of applying straw and biochar on Cu O NPs contaminated soil follows the order of 5%CB>5%CS>2%CB>2%CS.