MORPHOLOGICAL DISTRIBUTION CHARACTERISTICS AND BIOAVAILABILITY OF RADIONUCLIDE URANIUM OF FARMLAND SOIL IN A URANIUM DEPOSIT AREA

In this study, downstream farmland soil of tailing dam of a uranium deposit area in Southern Chinas was selected as research object, ICP-MS and laser fluorescence method were adopted to measure radionuclide uranium content and analyze uranium distribution in the soil and plants; sequential chemical extraction method was employed to analyze uranium occurrence form in soil, study uranium morphological distribution characteristics in soil; total quantity forecasting method and plant indication were used to analyze bioavailability of uranium in soil. The results showed that: average uranium content in the surface soil was 15.73mg / kg; average uranium content in rhizosphere soil was 16.58mg / kg; there was a good correlation between uranium content in surface soil, rhizosphere soil and plants. Uranium content in soil is mainly affected by irrigation water, which is higher in points closer to pollution sources; morphological distribution trend of uranium content in surface soil and rhizosphere soil is basically the same: residual form> carbonate bound form> organic bound form> amorphous iron and manganese oxides / hydroxide bound form> exchangeable form (including water soluble state)> crystalline iron and manganese oxides / hydroxide bound form. On the whole, rhizosphere soil exchangeable (including water soluble) uranium, carbonate bound uranium, organic matter bound uranium are higher than corresponding content in non-rhizosphere soil; Bioavailability of uranium in soil samples shows that: mobile uranium accounts for 30.66% of total uranium of 6 phase states, potentially mobile uranium accounts for 5.60% of total uranium of 6 phase states, which means more than 60% of uranium may pose threat and potential threat to the environment. Bioavailability coefficient is large, which preliminarily proves existence of potentially hazardous uranium in soil for plants. Through this study, distribution and accumulation in soil, occurrence form and bioavailability characteristics of radionuclide uranium in the study area are initially grasped, which can provide a theoretical basis for restoration of soil contaminated by radionuclide uranium.