Effect Of Sliver Nanoparticles And Silver Ions On Soil Microorganisms And Enzyme Activities

As a new type of inorganic antibacterial material,silver nanoparticles is widely applied in the daily.Therefore,silver nanoparticles has been released and accumulated in the environment,and eventually released into the environment after migration and transformation and would be gathered in the soil and water.From previous studies,the nano metal materials had a strong toxic effect on soil microorganisms and enzyme activities,but the effect of silver nanoparticles on soil microbial activities and soil enzyme activities was relatively seldom,and the toxicity of silver nanoparticles was still a controversy on whether silver nanoparticles dominant or silver ions.So this study selected silver nanoparticles and silver acetate(silver ions)as polluted materials,and the Hefei yellow cinnamon soil and Zhaoqing latosol soil was selected as the tested soil.This research compared the effect of silver nanoparticles and silver ions on soil basic properties such as pH,the content of organic matter and microbial biomass carbon.And this study discussed the toxicity effect of silver nanoparticles and silver ions on soil microbial diversity and soil enzyme activities.This research also studied the effect of silver nanoparticles and silver ions on cytotoxicity by measuring the fluorescence intensity and the proportion of death bacteria.The main research contents and results are as follows:1?The results showed that the concentration of silver nanoparticles had no effect on soil pH and the content of organic matter,but microbial biomass carbon decreased with the silver nanoparticles applying.With increasing the addition of silver acetate concentration,soil pH and organic matter content had a slight increase,soil microbial biomass carbon showed a decreasing trend,but the decline trend was not significant comparing with the microbial biomass carbon after adding silver nanoparticles.It may be that the concentration of silver acetate in soil is lower,the inhibition of soil microbial biomass is lower,and the silver acetate is carbon containing organic matter.2?The results showed that silver nanoparticles had certain toxicity effects on soil microorganisms(bacteria,fungi,actinomycetes),and with silver nanoparticles concentration increasing,the toxic enhanced and the microbial quantity significantly reduced.Silver ions also had certain inhibitory effects on soil microbial quantity,with the silver ions were applied,the inhibitory effect was increasing and the number of soil microorganism reduced.But from quantitative changes,the toxicity of silver ions to microorganisms was far lower than that of silver nanoparticles.It showed that the toxicityof silver nanoparticles on soil microorganisms was mainly from the silver nanoparticles itself rather than the dissolution of the ions.3?The results showed that the silver nanoparticles had strong toxicity on two types of soil's urease,invertase,FDA enzyme,catalase and with silver nanoparticles concentration from 0 mg/kg increased to 100 mg/kg toxicity increases ceaselessly,that silver nanoparticles had strong toxicity on soil microorganisms.But the results suggestted that silver ions had no effect on soil enzyme activity,regardless of the silver ions concentration increased to the test set of the highest concentration of 10 mg/kg,urease,invertase,FDA enzyme and catalase did not showed a inhibited trend in yellow cinnamon soil and latosol soil.The silver ions' concentration was set basing on silver nanoparticles' dissolution ion concentrations,was far below the records of silver ions' toxicity concentration,so it could be that the dissolution of silver ions was rarely,so its' toxicity effect on soil enzyme activity can ignore.Therefore,it can be explained that the inhibition effect of silver nanoparticles on soil enzyme activity is mainly caused by silver nanoparticles itself,which is not related to the dissolution of silver ions.4?By comparing the control group,20 ?g/mL silver nanoparticles treatment group and0.2?g/mL silver ions treatment group's fluorescence intensity of E.coli's and the proportion of death bacteria,the results showed that the fluorescence intensity of the control group and death cells ratio was far below the 20 ?g/mL silver nanoparticles'.And the control group compared to the 0.2 ?g/mL silver ions treatment on Escherichia coli and the fluorescence intensity and dead cells ratio's differences were very near.So the silver nanoparticles has strong toxic effects on Escherichia coli by damaging its cell membrane,the toxicity of the dissolution of silver ions concentration could be disregarded on Escherichia coli.