Effects Of Copper Oxide And Zinc Oxide Nanoparticles On Microorganisms In Forest Red Soil

The application of nanotechnology in modern agriculture has received much attention.Previous studies showed that the addition of nanofertilizers or some metal nanoparticles(MNPs)could not only provide nutrition for crops,but also control pests and diseases,and thereby increase crop yield.Copper oxide nanoparticles(CuO NPs)and zinc oxide nanoparticles(ZnO NPs)as two common materials in MNPs,common MNPs has been found to increase the growth and yield of crops probably by stimulating photosynthesis and respiration of plants,or by suppressing the growth of soil pathogens.Soil fertility represents the ability of soil to provide various nutrients needed for crop growth.Bacteria and fungi as the most abundant groups of living microorganisms,play essential roles in terrestrial ecosystem function,and can be useful to evaluate the biological activity of soil.Most studies have focused on the promoting effects of MNPs on crop growth and the adverse effects of MNPs on soil microbial community,while few have paid attention to the positive effects of MNPs on soil microbial community,and few have paid attention to the biological effect relationship between different forms of nanoparticles in soil and soil microbial community.In this study,the different dose of CuO NPs?ZnO NPs and their mixture were added to red soil to explore the effects of MNPs on the abundance,diversity and structure of soil microbial community.The relationship between the forms of MNPs in soil and their microbial effects was established to find out the key factors controlling the biological effects of MNPs.Based on the above analysis,and to test the following hypotheses:1)Relatively lower concentrations of CuO NPs and ZnO NPs(e.g.<500 mg kg^-1soil)may promote the soil microbial community richness and diversity.2)Dissolved and particulate forms contribute to the microbial impacts of CuO NPs and ZnO NPs,and the contribution depends on the types of MNPs.Through the experimental verification,the following results are obtained:(1)The hydrodynamic diameters of the CuO NPs increased significantly with increased concentrations and exposure duration.After exposure of CuO NPs and ZnO NPs in soil extract water for 14 days,the solubility rates of Cu and Zn in soil extraction water were lower than 0.8%.The relatively low concentration of CuO NPs and ZnO NPs increased the richness and diversity of bacterial and fungal communities,which was mainly reflected by the increase of the number of bacterial and fungal species and the increase of Alpha diversity index.However,the promotion of CuO NPs and ZnO NPs on the richness and diversity of bacterial and fungal communities was weakened by high concentrations of MNPs.(2)The qualitative and quantitative analyses of soil metal content and speciation with the addition of nanoparticles were conducted,and the correlation between the concentration of the different forms of MNPs in soil and microbial effects was explored.The results showed that both particulate and dissolved forms were involved in the effects of CuO NPs and ZnO NPs on the bacterial and fungal communities,and which played the dominant role was depended on the type of MNPs and microbes.(3)The relative abundances and Venn plots of bacteria and fungi under different treatments were analyzed,and it was observed that some microbial groups were very sensitive to the addition of CuO NPs and ZnO NPs.The results as well as the changes in the number of common and unique OTUs showed that the addition of MNPs affected the community structure of bacteria and fungi in red soil.ANOSIM similarity analysis showed that fungi were more tolerant to MNPs than bacteria.(4)The mixture of CuO NPs and ZnO NPs did not show more promotional effects on the soil bacterial community than the sum of individual effects.By comparing the effects of MNPs on bacterial and fungal communities in two different soils,the results showed that the addition of CuO NPs decreased the number and diversity index of bacterial species in the soil with lower organic matter content,which was contrary to the effect of ZnO NPs and its mixture.Impacts of CuO NPs on soil microorganisms was more easily influenced by environmental factors as compared with ZnO NPs.In summary,this study evaluated the effects of CuO NPs,ZnO NPs and their mixtures on the richness and diversity of bacterial and fungal communities in red soil without artificial fertilization.The positive effects of CuO NPs and ZnO NPs in agricultural applications can be predicted,but attention should be paid to the choice of dosage and the change of soil properties.