Ecotoxicological Effects Of Y₂O₃ NPs On Plants In Water

Nanomaterials?NMs? have been widely used in medicine,military industry and agriculture.Rare earth nanomaterials possess the characteristics of both rare earth elements and nanoparticles?NPs?,having a widely prospect of application and great potential for development in the fields of electricity,light,magnetism and catalysis.For example,yttrium oxide nanoparticles?Y₂O₃ NPs? is widely used in optical glass,military materials and ceramic material additives.During the preparation,application and disposal of NPs,it will inevitably enter rivers,lakes and other water bodies through various ways.As a kind of trace pollutant,the potential pollution and ecological effects of NPs on the water environment are also attracting more and more attention.In this paper,Y₂O₃ NPs and Y³⁺ released from Y₂O₃ NPs were selected as the research object and the control,respectively,and rice and tomato were chose as the tested plants.The ecotoxicological effect of Y₂O₃ NPs on the tested plants and the absorption,migration and transport of Y₂O₃ NPs by the tested plants were studied under hydroponic conditions.The main conclusions were listed as follows:?1?According to the TEM image and Zeta potential of Y₂O₃ NPs in ultra-pure water,it could be concluded that the agglomeration of Y₂O₃ NPs in ultra-pure water was remarkable,the stability was general,and it was easy to settle.The particle size mainly ranged between0.1?m⁰.15?m,and the average agglomerate particle size was 0.34?m.The sedimentation phenomenon of Y₂O₃ NPs in 1/2 Hoagland's nutrient solution was more significant than that in ultra-pure water.The concentration of Y³⁺ released from Y₂O₃ NPs in ultra-pure water was linearly correlated with the concentration of Y₂O₃ NPs?R²=0.97?.?2?From the seed germination,root length and bud elongation and biomass of the tested plants,it could be seen that Y₂O₃ NPs and its released Y³⁺ had no significant effect on the germination rate of these two tested plantseeds,but the high concentrations of Y₂O₃ NPs?50mg/L and 100 mg/L? could delay the germination of the seeds.Y₂O₃ NPs showed a phenomenon of"low concentration promotes and high inhibition".Y₂O₃ NPs solution at low concentrations of 1¹0 mg/L had a positive effect on the rice root elongation.However,when the concentrations of Y₂O₃ NPs solution reached to 20¹00 mg/L,a significant inhibition effect on the rice root elongation emerged.The bud elongation wasn't affected by Y₂O₃ NPs and its released Y³⁺.The 20¹00 mg/L Y₂O₃ NPs could inhibit the root and bud elongation of tomato and reduce the biomass of both two tested plants.The semi-inhibitory concentration of rice root elongation?17.4mg/L? was slightly higher than that of tomato?13.4mg/L?.?3?Y₂O₃ NPs of 20¹00 mg/L had significant inhibition effects on chlorophyll content and root activity of the two tested plants.It could also produce toxic effects on plants by affecting their antioxidant capacity,which shows that SOD activity significantly decreased and could not completely remove the accumulated ROS.Then,ROS stimulated membrane lipid peroxidation in rice and tomato cells to produce MDA,thus inhibiting the production of plant protein and leading to low protein content.?4?Y₂O₃ NPs and Y³⁺ released from Y₂O₃ NPs could be absorbed and accumulated by the roots and transported to the shoots,and Y content in the roots was much higher than that in the shoots.Under Y₂O₃ NPs treatment,the Y transport coefficients from the roots to the shoots of rice and tomato were 1.94%-7.55% and 0.27%-21.28%,respectively.TEM observation showed that Y₂O₃ NPs could enter the mesophyll cells of rice and tomato,and existed in the cell wall,intercellular space and cytoplasm of the mesophyll cells,which could also cause damage to cell organs..Endocytic vesicles are the way for Y₂O₃ NPs to enter plant cells.?5?In total,Y³⁺ released from Y₂O₃ NPs had no significant effect on the plant growth and the ecotoxicological effect of Y was mainly produced by Y₂O₃ NPs.