Influence Mechanism Of Water Management On The Occurrence And Accumulation Of Uranium In Soil-rice System

Using the uranium-contaminated farmland soil in a certain area as the cultivation substrate,the pot experiments were carried out using flooding irrigation,alternating dry and wet irrigation,moist irrigation and local farmer irrigation to study the changes of uranium in the rice rhizosphere soil under different water management modes.Uranium pollution in rhizosphere soil and its main influencing factors were analyzed;combined with soil p H value,organic matter content and iron film content of rice root surface,the effect of water management on uranium bioavailability in soil-rice system was explored;The uranium content in each organ of rice under the management mode was used to explore the migration,accumulation and spatial distribution of uranium in rice;the optimal water management mode was used as the irrigation method,and the soil with uncontaminated soil mixed with different concentrations of uranium solution was used as the cultivation substrate to explore the different uranium pollution.The bioavailability of uranium by rice in the soil;taking different genotypes of rice as the research object,the uranium-contaminated farmland soil and the non-polluted soil mixed soil in proportion as the cultivation substrate,to explore the bioavailability of different genotypes of rice to uranium.The main conclusions are as follows:(1)The bioavailable content of uranium in the rhizosphere soil reaches 55% to 70% of the total U.It increases first and then decreases with the rice growth stage,and shows a maximum value at the heading stage,while the redox The potential value(Eh)decreased at heading stage.(2)Taking the soil uranium content after air drying as the benchmark,it is convenient to accurately compare the variation trend of uranium content in the rice rhizosphere soil with the growth period and the factors affecting the change of uranium content under different water management modes.The uranium content in the rhizosphere soil of rice decreased first and then increased with the growth period;flooding irrigation and alternating dry and wet patterns helped to reduce the uranium pollution in local farmland soil;the wet irrigation model had stronger bioavailability of uranium;water management It has a significant effect on soil p H,Eh value and organic matter content.(3)Due to the influence of temperature and rice growth period,the proportion of bioavailable uranium in rhizosphere soil at heading stage of rice planted in summer was higher than that in spring.(4)Most of the uranium absorbed by rice from the soil is concentrated in the roots;the enrichment capacity of uranium from rice,the transport and absorption capacity of rice to uranium in roots,the content of iron film on the surface of rice roots,the quality of rice at maturity and different uranium concentrations Based on the analysis of soil and different genotypes of rice experimental results,it was concluded that the optimal water management mode was the alternate dry and wet mode.(5)In soil experiments with different uranium concentrations,the enrichment of uranium by rice rhizosphere soil and the absorption of uranium by rice reached a dynamic balance within the range of 100 mg/kg;The size of the bioavailability: Nipponbare >9311 > Huang Huazhan > Local rice.Experiments showed that the local rice varieties were more able to effectively reduce the bioavailability of uranium under the alternate dry and wet irrigation mode.