Study On The Distribution And Chemical Species Of Plutonium In The Contaminated Soil Particles

Study on the distribution of Pu in soil particles plays a significant role in waste disposition. It is significant for predicting the parameters of Pu resuspension and improving the safety or radiological protection under suppose condition. Experimental date of the Pu species in the contaminated soil particles can be used to evaluate the mobility and biologic effects of Pu, offer basic date for modeling Pu transports in the area. Physical and chemical properties of soil are important factors because of the distribution and chemical species of Pu in the soil particles related to soil units and their stability.Wet classification and gravitational sedimentation method have been applied to characterize the soil-structure. The results indicated that the soil-texture is sandy loam. Based on national standards and relational reports, physical and chemical properties of soil were indicated that it is a typical alakalized desert soil with lower water content, organic, CEC and nutrient preservation under drastic oxidation condition, and no benefits for agriculture. Primary mineral is the chief constituents in soil mineral, quartz is the dominant composition in soil which exists in coarse-grain. The content of quartz is decreasing with the smaller particles. The chief secondary mineral is layer silicate, which exists in clay particle. Soil is still in its infancy weathering stages.Activity concentration of Pu in soil particles was measured by gamma spectrum in non-destructive condition. It was found that nearly 90% of Pu exits in 0.1-10mm particles, low than 10% of Pu exits in the particles that under 0.05mm, it is very harmful to biosphere by resuspension of soil. Activity concentration of Pu in each particles is more than 45000Bq/kg, volume of the contaminated soil can not be decreased by wet classification under supposed condition.A modified sequential extraction method of Tessier was applied to study the chemical species of Pu in soil particles. The results showed that 0.3%of Pu existed in exchangible state,1.4% bound to carbonate, 15.6% existed in Fe/Mn oxide,51.1% bound to organic,and 31.7% existed in residual. These results indicated that Pu was difficult to migrate in sandy loam. There was a significant linear relationship between the content of pu and organic (>0.1mm particles, the correlation coefficients r=0.97;<0.1mm particles, the correlation coefficients r=0.79), there was also a identically linear relationship between the content ofpu and illite (the correlation coefficients r=0.79). Chemical species of Am in soil particles was also studied and found which was different from that of Pu, but there was a more strongly linear relationship between the content of Am and illite or organic.