Study On The Release And Migration Characteristics Of Uranium,Thorium And Some Heavy Metals In Uranium Tailings And Soils Around

Uranium tailings were deposited in the open air by weathering, rain, surfacerunoff and the other external inlfuence, the radioactive elements （U，Th，etc） and toxicmetal elements would be washed out, leading uranium tailings to become potentialradioactive-metal composite pollution sources. The paper combined the ifeld researchand simulated test in the laboratory, analyzing the horizontal and vertical migrationregularity of the radioactive elements uranium&thorium and some heavy metalelements of soil in study areas. Under simulated natural environmental conditions, asemi-dynamic leaching test was carried out for studying the release behaviors ofelements and their correlations.（1）154of samples were yielded by the simulated leaching test during22weeks,,and the physical and chemical properties of the samples were analyzed.Determinations of the concentrations of uranium&thorium and seven kinds of heavymetal elements were carried out with the instruments of ICP-MS and ICP-AES，respectively. According to Fick diffusion theory, the linear regression analysis andcorrelation analysis of the data were used. The release behaviors, release mechanismand their correlations of elements were studied.The results showed that the release amount of uranium in uranium tailings wasmuch higher than thorium under simulated natural environmental conditions; theuranium tailings from minimum to maximum particle size were leached withdeionized water, the elements leaching mechanism was mainly controlled by thesurface dissolution, and the smaller particle size，the higher amount of the elementsleached; under the condition of strong acidity, the elements leaching mechanism wasalso mainly controlled by the surface dissolution, and generally the stronger theacidity, the higher amount of the elements leached; pH value and the particle sizeinfluenced the correlations of elements in the process of release. Reducing particlesize and the pH value, the correlation between the element uranium and part of heavymetal elements was enhanced, but the correlation between the thorium and otherelements was unobvious.（2）76of soil samples of the study areas were collected, their contents ofradioactive elements uranium&thorium and seven kinds of heavy metal elements were measured. The contents of radioactive nuclides²³⁸U，²²⁶Ra,²³²Th and40K in thesoil were measured by丫-ray spectrometer. The release behaviors, release mechanismand their correlations of elements were obtained.Preliminary research showed that the concentration of the radioactive element U，Th and heavy metals like Cd, Zn were high in soil of the study areas, heavy metalferrum concentration was signiifcantly high; the migration of elements existed acertain degree of correlation. the lateral migration patterns of elements in soil werethat the concentrations of the elements U，Th，Fe，Mn，Zn and Ni were decreased withthe increase of distance from uranium tailings dam; Vertical migration patterns werethat the elements concentrations rose or changed unobvious with the increase of thedepth. This part was preliminary study, in order to look for patters and providedirection for further study.This study would be of instructions for better understanding the pollution ofradioactive and heavy metals in uranium mining areas. It may has positivesigniifcance for establishing measures of pollution preventions.