NZVI/C Enhanced Phytoremediation Of Cadmium-Synthetic Musks Soil Pollution

Cadmium(Cd),Tonalid(AHTN)and Galaxolide(HHCB)constitute complex heavy metal-emerging contaminants pollution in the soil.Nanomaterials have been gradually applied to the field of soil remediation due to their excellent properties.Phytoremediation is a green soil remediation technology with broad application prospects.The combined application of nanomaterials and phytoremediation provides new ideas for soil heavy metal-emerging contaminants pollution remediation.This thesis takes Cd-HHCB/ANTH single and compound contaminated soil as the research object,and takes Tagetes patula L.as the test organism.Through pot experiment,the effect of nano-iron-carbon composite material(nZVI/C)on the phytoremediation effect of single and combined soil pollution was studied.At the same time,the effect of nZVI/C on the adsorption and desorption of single and composite pollutants in soil is studied.Combining with the research on the rhizosphere soil extract of Tagetes patula L.and the changes of rhizosphere microbial community,the mechanism of enhanced restoration was investigated.The main results are as follows:In the adsorption and desorption experiment,the adsorption isotherms of the three pollutants were more consistent with the Freundlich model.The adsorption capacity for a single pollution is:Cd>ANTH>HHCB.There is a hysteresis effect in the adsorption and desorption of HHCB and Cd by soil.The addition of nZVI/C increases the amount of soil adsorption of pollutants to a certain extent,reduces the amount of adsorption,and increases the hysteresis coefficient.It shows that the addition of nZVI/C and activated carbon slows down the release of ANTH,HHCB,and Cd in the soil.In addition,Cd in the soil reduces the amount of HHCB and ANTH desorption.The measurement results of the Tagetes patula L.biological indicators show that,no matter it is single or compound pollution conditions,when ANTH and HHCB are at lowconcentration pollution levels,the addition of nZVI/C significantly increases the biomass and plant height of Tagetes patula L However,under the high pollution level,the biomass and plant height are significantly reduced when nZVI/C is added.Further,it was found decreases with increasing levels of contaminants,biomass and height ratio.It was determined by pot experiment that the addition amount of nZVI/C was 0.20 g/kg.The addition of nZVI/C improves the removal rate of Tagetes patula L.on single and compound pollution of soil to a certain extent.Without the addition of nZVI/C,the highest removal rates of ANTH,HHCB,and Cd in single pollution were 57.70%,96.24%,and 50.31%,respectively,and the highest removal rates of ANTH,HHCB,and Cd in combined pollution were 8.86%,75.66%,and 48.94%,respectively.With the addition of nZVI/C,the highest removal rates of ANTH,HHCB,and Cd in single pollution were 63.55%,95.36%,and 53.61%,respectively,and the highest removal rates of ANTH,HHCB,and Cd in composite pollution were 30.67%,77.94%,and 39.62%,respectively.The application of nZVI/C can improve the removal rate of pollutants,which has the expected strengthening effect.In the experiment of plant absorption of pollutants,the addition of nZVI/C enhanced the absorption capacity of Tagetes patula L.to the pollution.At the same time,the results of pollutant concentrations in the ground and underground parts show that the addition of nZVI/C promotes the transportation of pollution to the ground parts.The results of the substance analysis of rhizosphere soil extracts showed that there was a significant correlation between the 6-Propyltridecane,2,6,11-Trimethyldodecane,Isopropyl myristate in rhizosphere soil extract and pollutant removal rate(correlation coefficient>0.71,P<0.05),and a strong correlation between Methyl isoheptadecanoate and the initial concentration of pollutants(correlation coefficient=0.93,p<0.1).Under combined pollution conditions,the VIP value of Eicosane is>1,which has a significant correlation with the removal rate of ANTH under combined pollution conditions(correlation coefficient=0.98,P<0.1),which may be the degradation byproduct of ANTH or a key substance contributing to the degradation of ANTH.The above-mentioned substances may play a positive role in the removal of pollutants or be products of the pollutants degradation.In the high-throughput sequencing of rhizosphere microorganisms,the Chao1 index and Shannon index values show that nZVI/C and pollutants promote the growth and reproduction of rhizosphere microorganisms and increase the number of microorganisms,but the microbial diversity is slightly reduced.This may be related to the changes in the chemical substances of the root soil under the experimental conditions,indicating that the Tagetes patula L.rhizosphere is an important participant in the restoration of soil pollution.In summary,under the test conditions,for the target pollutants,nZVI/C played a certain strengthening role in the process of remediation of soil pollution by Tagetes patula L..