Rhizosphere Effects Of Ryegrass On Extraction And Remediation Of Uranium-contaminated Soil Plants

In this study,ryegrass was selected as a test plant,and under the conditions of uranium pollution at different levels,the ryegrass root box cultivation experiment were carried out to study the biomass of ryegrass under natural conditions and citric acid application,characteristics of uranium-enriched uranium and spatial variability of rhizosphere uranium,uranium morphology,transformation and analysis,and rhizosphere effects under uranium stress.The main results of the study are as follows:?1?Study on the interaction mechanism between ryegrass and uraniumThe uranium-tolerance study results of ryegrass seeds showed that ultra-low uranium concentration can promote seed germination and growth.When the uranium concentration is more than 5 mg/L,the seeding degree and regularity of ryegrass seed were affected by different concentrations of uranium treatment liquid.The degree is different.The results of root box experiment showed that higher uranium concentration decreased the biomass of ryegrass.The enrichment pattern of uranium in the ryegrass plant body was root>aboveground part,and the concentration of uranium in rectangular root box was 20 mg/kg.Root absorption reached a maximum of 831.9 mg/kg.There was a threshold at the root enrichment of ryegrass,and the root transport capacity reached a maximum at this time.The transport coefficient of ryegrass is less than 1,indicating that the ability of the root to transfer to the aerial parts is low.The spatial dynamic changes of uranium in the rhizosphere soil indicate that the uranium content in the rhizosphere>the non-rhizosphere uranium content;and the increase in the uranium concentration also favors the enrichment of uranium in the rhizosphere soil.Under different uranium concentrations,there are obvious differences in the distribution of uranium in the rhizosphere and non-rhizosphere soils.The percentage of active and potential active uranium in the rhizosphere soil is higher than that in the non-rhizosphere soil.The mean value of the carbonate bound state of uranium in the rhizosphere soil in the rectangular root box was as high as 22.77%,and the proportion of active uranium was the highest.The pH value in rhizosphere soil decreases with the increase of uranium concentration.The decrease of pH value is favorable to the absorption of uranium in soil by ryegrass.The content of organic matter in rhizosphere soil was higher than that in non-rhizosphere soil.The higher the content of organic matter,the more harmful the absorption of uranium in soil by ryegrass.?2?Interaction mechanism between ryegrass and uranium induced by citric acidThe application of citric acid changed the physicochemical properties of uranium-contaminated soil,organic matter content in rhizosphere and non-rhizosphere soil,uranium content in rhizosphere soil,biomass of ryegrass,enrichment of above ground and roots,and transport coefficient of enrichment coefficient.Both increase with increasing citric acid addition.The addition of citric acid activates the inert uranium in the soil.A portion of the residue state and the crystalline iron-manganese oxide/hydroxide binding state are converted into carbonate-bound and exchangeable states that can be absorbed by the plant.The content of organic matter in rhizosphere soil was higher than that in non-rhizosphere soil.After application of citric acid in rectangular root box and round root box,the content of organic matter in soil in rhizosphere soil was 1.36 and 1.31,respectively,in organic soil without citric acid.Times.In addition,the rhizosphere soil environment is a dynamic environment in which the plant's rhizosphere releases citric acid and the applied citric acid forms a root-citric acid-rhizosphere soil.?3?Study on mechanism and rhizosphere effects of uraniumScanning electron microscopy?SEM?analysis and EDS spectrogram analysis showed that there are a lot of adsorption sites of UO₂²⁺on the soil surface,which is an important factor affecting the ability of plants to adsorb uranium;the surface of plant ash samples are aggregated with uranium of different shapes and sizes particle.The correlation analysis and cluster analysis of the uranium forms in the rhizosphere soil showed that there was a positive correlation between uranium of various forms and total amount,and there were positive and negative correlations between different forms of uranium.According to the changing trend of uranium in the rhizosphere soil,the uranium in the rhizosphere soil can be divided into four types.The reduction in pH and the use of exogenous citric acid promotes the enrichment of uranium in the rhizosphere of plants and the conversion of inert uranium in plant roots,which increases the bioavailability of uranium and converts it to be absorbed or potentially absorbed into the other forms.