Effects Of Sodium Percarbonate On Herbicides And Microbial In Soil

Sodium percarbonate is a kind of solid peroxide with high oxidation activity.It can react with Fe(II)to produce hydroxyl radical,which can oxidize most organic compounds.Therefore,the study was carried out in order to explore the optimal conditions for the degradation of herbicides in soil and the effect on soil microbial diversityThe research content has the following three aspects:(1)Using the luminol chemiluminescence system to explore the oxygen evolution mechanism of sodium percarbonate dissolved in water,to observe The change of luminescence intensity after the reaction after the addition of Fe(?)in the system,in order to verify the effect of Fe(?)on the decomposition of sodium percarbonate.(2)Simulated 2,4-dichlorophenoxyacetic acid contaminated soil,to measure the degradation rate of 2,4-D by sodium percarbonate in soil by changing the amount of sodium percarbonate,sodium percarbonate / Fe3+ mass ratio,soil moisture content,temperature and other conditions.(3)To change the content of sodium percarbonate and the time of action of sodium percarbonate,and then detect the change of microbial diversity in soil by 16 s s RNA high throughput sequencing.Result:(1)In the H2O2-luminol system,the change of H2O2 concentration did not affect the luminescence intensity.But when the concentration of Na2CO3 was increased to 0.1 mol/L,the luminescence intensity increased first and then decreased,and then slowly recovered to 300,000 cps(counts/s);when the mass of sodium peroxydicarbonate is 0.01 g,the luminescence value is kept at about 300,000 cps.After adding Fe2+ into the reacting system,the luminescence value rises sharply.(2)When adding sodium percarbonate in soil alone,the content of 2,4-D did not change significantly,when the mass ratio of SPC:Fe3+: 2,4-D is 100:10:1 and 150:15:1,the degradation rate of 2,4-D reached the highest level,61.65% and 60.16% respectively,and the degradation rate of 2,4-D is the highest when the moisture content is 28.57% and the temperature is 20 ? the highest degradation rate.(3)Compared to the control group,microbial community composition changed significantly in the experiment group which added in 5.0 g sodium percarbonate,and the Proteobacteria and Sphingomonas relatively decreased,Arthrobacter,Firmicutes,Bacillus increased obviously,and the relative content increased over time.The results show that the presence of sodium carbonate can reduce the oxygen release rate of H2O2,and ensure the efficiency of oxygen release of H2O2,so that H2O2 can maintain a slow and stable decomposition in water.However,after the addition of Fe2+,the luminescence value increased significantly,which indicated that the Fe2+ lead to the change of the dominant way of H2O2 decomposition,and the hydroxyl radical with strong oxidation activity was decomposed.In the soil SPC:Fe3+: 2,4-D mass ratio of 100:10:1 is more conducive to the degradation of 2,4-D.The decomposition of sodium percarbonate produces hydroxyl radical with strong oxidation activity,and enhanced chemiluminescence.In the soil SPC:Fe3+: 2,4-D mass ratio of 100:10:1 is more conducive to the degradation of 2,4-D.The relative content of Firmicutes,bacillus which adapts to the extreme environment increased after the addition of sodium carbonate,which indicated that sodium carbonate resulted in the decrease of soil environmental quality,and the environment suitable for microbial growth and reproduction was destroyed with the increase of the amount of sodium carbonate.