Studies on Speciation of Environmental Plutonium

为了改进对陆地生态系统放射性核素污染的影响评估，放射性核素物种的信息是必不可少的。土壤中储存的放射性核素可能以不同的物理化学形式存在，从可移动的低分子质量离子物种到惰性高分子质量胶体或颗粒。在这项工作中，试图表征土壤中的钚。为此目的，前苏联塞米巴拉金斯克核试验场的原子武器近距离落下的高污染土壤样品来自Dolon定居点。首先对Dolon定居点的土壤样品进行了γ放射性核素(~(137)Cs和天然放射性核素)的测定。然后测定了Pu，我们采用逐步淋洗法获得了Pu与土壤的地球化学结合信息。~(137)Cs和~(239,240)Pu的储量分别在790~10,310和530~14,320 Bq/m~2的大范围内。土壤中Pu的连续淋溶表明，~(137)Cs和~(239,240)Pu的储量分别在790~10,310和530~14,320 Bq/m~2之间发现的PU不是用COCC热消化的。HNO_3+H_2O_2，表明Pu的存在与来自局部散落碎屑的熔融硅酸盐有关。此外，使用CR-39聚碳酸酯的α径迹照相技术在土壤中证实了钚污染物中热粒子的存在，即使在第一次核武器试验约50年后的今天也是如此。

To improve impact assessments of radionuclide contamjnation in terrestrial ecosystem, informationon radionuclide species is essential.Deposited radionuclides in soil may be present in different physico-chemical forms, ranging from mobile low molecular mass ionic species to inert high molecular mass colloidal forms or particles.In this work, an attempt was made to characterize Pu in soil.For this purpose, highly contaminated soil samples by close-in fallout from atomic weapons tests at the former Soviet Union's Semipalatinsk nuclear test site were collected from Dolon settlements. This settlement was heavily exposed by the close-in fallout from the first nuclear test on 29 August 1949.The soil samples from Dolon settlement have been first measured for γ-emitting radionuclides(^<137>Cs and natural radionuclides).After that, Pu was determined, in which we employed the stepwise leaching method to get information on the geochemical association of Pu with soil.The inventories of 137Cs and 239,240Pu were in the wide range of 790-10,310 and 530-14,320 Bq/m^2, respectively.Sequential leaching of Pu from the soil showed that more than ca.80% of the ^<239,240>Pu found were not leached by hot digestion with conc. HNO_3 +H_2O_2, indicating the presence of Pu associated with fused silicates originating from local fallout debris. Furthermore, the presence of hot-particles from the Pu contaminants by α-track radiography technique using CR-39 polycarbonate was confirmed in the soil, even at present after about 50 years from the first nuclear weapon testing.