Study On Ecological Self-recovery Of Soil Microorganisms Exposed To Nano-zinc Oxide

ZnO ENPs,as an important raw material for industrial products,has been increasingly used in daily life,its environmental exposure and ecological risk problems cannot be ignored.Soil microbes are the core elements of soil ecosystems.It undertakes the ecological functions of the soil,participates in biogeochemical cycles,and affects the structure and function of the animal and plant communities.This paper mainly studied the ecological elasticity of soil microorganisms after Zn O ENPs exposure in different ways and at different levels,ie,the self-recovery trend and level of their community structure and metabolic function.The study found:Based on the evaluation of the antioxidant system,the effect of ZnO ENPs of soil microorganisms was studied.The cell metabolism?H₂O₂ and MDA?product content and antioxidant enzyme concentration?T-AOC,T-SOD,GSH-PX?showed:the resistant bacteria is better than control,and the mixed bacterium is better than the pure,maximum exposure concentration is 200 mg/L.The fit of peroxidative stress/antioxidant response factor and ZnO ENPs concentration was consistent with the toxicological effects and showed a significant dose-effect relationship within a certain range.In the acute and chronic ZnO ENPs exposed contrast experiment,compared with contrast,the performance of the carbon source utilization and soil microbial community functional diversity are acute inhibition,chronic activation,and mostly in the upper inhibition,lower activation.When the carbon sources metabolic activity of chronic exposure was restored,the original carbon source utilization characteristics changed,and carbohydrate metabolism was significantly activated.In soil exposure,regardless of exposure concentration ZnO ENPs changed soil microbial carbon source metabolism and community structure.10 mg/kg?soil?Zn O ENPs had the least impact on carbon source metabolism,and the longer the culture time,the higher the similarity with the control group.The carbon source metabolic activity and functional diversity of the 100 mg/kg and500 mg/kg exposure all fluctuate with the incubation time,but the carbon source metabolism characteristics will be closer to the control with the extension of culture time.In terms of community structure,population abundance and species diversity are all decrease in the 30th days and negatively correlated with exposure concentration.In the 90th and 120th days,the diversity of the communities increased and converged,but the difference in composition became larger and could not be recovered.Different bacteria species were differently affected by ZnO ENPs,and the abundance of the core population was short-term promotion,medium and long-term inhibition,and both were positively correlated with exposure concentration.Among them,the Firmicutes was activated,the higher the exposure concentration and the longer the incubation time,the activation is stronger.The Actinobacteria was inhibited,this effect was higher along with the exposure settings.The effect on Proteobacteria is very small.In general,the higher the exposure concentration,the greater the influence of soil microflora,and culture time are the key influence factors:the carbon source metabolism and community structure characteristics of the experimental groups are basically different in the early culture period and the middle and later.In the soil ecological changes,different concentrations of ZnO ENPs made soil acidification after 120 days of exposure.Zn O ENPs increase the soil total organic carbon content,but humic acid and fulvic acid formation are significantly suppressed,soil humification degree increased and restore to control level in late period.Soil particle agglomeration under 500 mg/kg,while the other two groups did not appear.In conclusion,ZnO ENPs change soil physical and chemical properties by interfering soil microbial activity and community composition.During the period of 120 days,irreversible changes have been made on the pH,organic carbon.Soil microbial biomass,carbon source metabolism,and community structure have also been changed.Therefore,soil microbial ecological show some flexibility but has not yet recovered.