Study On The Mechanism For Electric Field Enhancing Remediation Of Uranium And Cadmium Co-Contaminated Soil By Macleaya Cordata

Uranium and cadmium are two metals that naturally exist in water and terrestrial environments,so their existence in the environment is usually more stable and poses less harm to human health.However,the current rapid development of industry and agriculture has led to an increase in generation of waste products,pollution of irrigation water and uranium and cadmium pollution in soil,and the accumulation of uranium and cadmium in the food chain,which ultimately poses a serious threat to human health.Therefore,in order to prevent the bioaccumulation of uranium and cadmium and reduce its threat to human health,it is urgent to carry out research on the purification of uranium and cadmium in soil.Plant remediation is a promising environmentally friendly method for remediation of heavy metal pollution,but it also has certain disadvantages,such as long remediation cycle and low efficiency.The external electric field can make up for the shortcomings of phytoremediation by improving plant biomass,changing the chemical form of pollutants,and promoting the migration of pollutants,and improve the efficiency of phytoremediation.Therefore,electric field-enhanced phytoremediation technology is anextremely effective method for remediation of uranium-cadmium compound contaminated soil.In this study,on the basis of Macleaya cordata's remediation of uranium-cadmium composite contaminated soil,adding a 0.3 V/cm DC electric field,and the behavior and mechanism of electric field enhancement of Macleaya cordata's remediation of uranium-cadmium composite contaminated soil were studied.The mechanism of phytoremediation enhanced by external electric field was proved by studying the low of changes in biomass,bioaccumulation abilities for uranium,and antioxidant enzyme activity of Macleaya cordata,changes in the existing form and valence state of uranium and cadmium,and changes in microbial community structure and organic acid content in rhizosphere soil.The results showed that the plant height,root length and dry weight increase after the application of DC electric field,and the total biomass increased by 15.33%~29.88%.The enrichment effect was also significantly improved,in which the uranium content and cadmium content of the above-ground parts in the DC+U and DC+Cd treatment groups were increased by 91.34% and 93.06% compared with the U and Cd treatment groups,and the uranium content and cadmium content of the underground part were increased by 100.02% and 67.43%,and the enrichment factor was increased by 90.84% and 93.33%.The content of organic acid also increased,and the citric acid content in the electric-field applied group increased from below detection limit to detectable compared with that in the unelectric-field applied groupunder corresponding conditions.Meanwhile,the contents of oxalic acid,tartaric acid,succinic acid,malic acid,and lactic acid were increased by18.36%~45.31%,58.62%~503.22%,15.71%~118.99%,12.34%~123.27%,and 25.97% ~36.05%.The content of antioxidant enzymes in plants increased,POD and gsh-px increased by 13.63%~34.82% and9.70%~28.64%,respectively.After being treated by an applied electric field,the valence state of most of the uranium in the root of Macleaya cordata changed,and most of the uranium in the root of Macleaya cordata changed from stable U(IV)to U(VI),which was more easily transferred from the underground part to the aboveground part.The proportion of plant-usable uranium and cadmium in the rhizospheric soil was increased significantly.The proportion of bacteria such as Acidobacteria and fungi Ascomycota increased,and these microorganisms enhanced Macleaya cordata tolerance and enrichment of uranium and cadmium by increasing enzyme activity.Therefore,the application of an electric field to strengthen phytoremediation is a faster and more efficient method than conventional phytoremediation.