Study On MgO Nanoparticles Inhibiting The Toxicity Of Cadmium To Garlic

With the increasing use of nanomaterials,the diffusion of nanoparticles into the natural environment is becoming more and more serious.The synergy between these artificial nanomaterials and some of the original heavy metal pollutants in the environment and the complex biological effects they bring have also attracted more and more attention.The influence of MgO nanoparticles on the biotoxicity of heavy metal Cd has always been paid attention to,and many studies have been conducted.An important shortcoming in this type of research is the lack of real-time dynamic measurement of Cd²⁺concentration and Mg²⁺concentration released from MgO nanoparticles.This is mainly because the currently widely used ICP-AES method is limited by the measurement principle and sample preparation procedures and cannot perform real-time dynamic measurement of ion concentration.In response to this problem,the Cd²⁺and Mg²⁺selective microelectrodes were successfully prepared in this thesis to solve the problem of real-time dynamic measurement of Cd²⁺and Mg²⁺concentration.On this basis,garlic was selected as a test plant to study the synergistic effect of nano MgO and heavy metal Cd on the growth of garlic roots,especially the inhibitory effect of MgO nanoparticles on the biotoxicity of heavy metal Cd.The study found that the garlic root elongation was respectively reduced by about40.5%,45.3%,77.6%and 91.9%,under 1.0,2.0,3.0,and 4.0 mg/L Cd²⁺stress compared with the control group.After adding 80.0 mg/L MgO NPs in different Cd²⁺treatment groups,the root length of garlic improved significantly under the treatment of Cd²⁺solution alone,increasing by about 34.3%,48.3%,45.6%and 18.8%,respectively.30.0 mg/L Mg²⁺can also inhibit the toxicity of Cd²⁺.Compared with the Cd²⁺alone treatment group,the root length increased by approximately 29.4%and17.3%in 1.0 and 2.0 mg/L Cd²⁺+Mg²⁺treatment groups,respectively.In order to dynamically measure the concentration of Cd²⁺and Mg²⁺in the solution in real time,the detection limit of the Cd²⁺selective microelectrode prepared in this thesis is about 4.47×10^-6 mol/L,which has good linear performance in the range of the calibration solution concentration of 10^-5?10^-2 mol/L,and the detection accuracy is 2%.The detection limit of Mg²⁺selective microelectrode is about 2.18×10^-5 mol/L.It has good linear performance in the range of calibration solution concentration of 10^-4?10^-1 mol/L,and the relative error is less than 4%.The ion concentration measurement results showed that the Cd²⁺concentration of1.0 to 4.0 mg/L decreased by about 86.4%,85.5%,88.3%,and 87.7%,respectively,at6 h.After the addition of MgO NPs,the Cd²⁺concentration in the four treatment groups decreased to almost 10%of the initial concentration at about 2 h.This shows that in addition to the absorption of Cd²⁺by garlic,MgO NPs also have a certain adsorption effect on Cd²⁺.When Cd²⁺+MgO NPs cultured garlic,the saturation value of Mg²⁺concentration after 48 h was lower than the saturation value of Mg²⁺concentration naturally released by MgO NPs,indicating that garlic has certain absorption of Mg²⁺.The Cd²⁺concentration in the Cd²⁺+Mg²⁺treatment groups decreased more slowly than the Cd²⁺alone treatment group,but the Cd²⁺concentration of each group also decreased by almost 90%at 46 h,showing that Mg²⁺has limited inhibitory effect on garlic consumption of Cd²⁺.Interestingly,no matter whether the MgO NPs or Mg²⁺group was added,the significant decrease in Mg²⁺concentration occurred after 20 h,which may be due to the sufficient nutrients of garlic itself.Garlic showed absorption of Mg²⁺after a period of consumption.By fitting the ion concentration change curve,it was found that after adding MgO NPs,the absorption value C_m of garlic to Cd²⁺becomes smaller than that of the Cd²⁺treatment alone group.The Mg²⁺released by the MgO NPs in the garlic cultured group had a higher saturation value C_p than the uncultured group,indicating that Mg²⁺was continuously released by MgO NPs while being absorbed by garlic.The above research results indicate that MgO NPs adsorb part of Cd²⁺,in addition,the Mg²⁺released by it is partially absorbed by garlic,which alleviates the biological toxicity of Cd²⁺.In this thesis,the ion-selective microelectrode technology is used to achieve the dynamic measurement of Mg²⁺and Cd²⁺concentration,which makes up for the shortcoming in the existing nano-biological effect research.The curves of Cd²⁺and Mg²⁺concentration change with time were obtained,and the quantitative analysis of the kinetic process of the Cd²⁺and Mg²⁺concentration change process was carried out.Therefore,we reached a deeper understanding of the detoxification mechanism of MgO NPs on the heavy metal Cd²⁺in garlic.The results of this study are of great significance for understanding the role of metal ions released by metal oxide nanoparticles in the biological effects of nanoparticles.