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为了研究黄土包气带中放射性核素在垂直和水平方向上的二维迁移 ,在野外试验场的 C坑 (天然条件 )和 F坑 (人工喷淋条件 )进行了取样测量。将 85Sr、13 4Cs和 60 Co三种核素与黄土均匀混合 ,制成示踪源 ,埋置于坑底中心位置 ,距地表 1m,两坑示踪源层尺寸均为 5.5cm× 0 .6 cm。分别于埋置示踪源层后的第 783d(F坑 )和 10 72 d(C坑 )进行解体采样。使用专门制作的采样定位环 ,分层、分环采样。垂向分层 ,每层厚 1cm;水平方向分环 ,环的直径为 3～ 2 7cm,分 9种尺寸。在 C坑和 F坑分别采土样 2 4 1和 2 13个。用 Na I(Tl)γ谱仪测量土样中85Sr、13 4Cs和60 Co的活度 ,得到两坑中三种核素的比活度分布曲线。结果表明 ,13 4Cs和 60 Co的比活度峰在两试验坑中垂向迁移距离均小于 1cm,但也有一小部分迁移距离较大 ;而 85Sr的比活度峰在人工喷淋条件 (喷淋强度 1.5cm/d)的 F坑 ,向下迁移了约 13cm,在天然条件的 C坑 ,比活度峰仍在示踪源层 ,但在上、下二个方向上明显展宽。另外 ,还发现在水平方向上径向距为 11.3cm(F坑 )和 12 .8cm(C坑 )样品中也有三种核素的存在
In order to study the two-dimensional migration of radionuclides in the vertical and horizontal directions in the loess aerenchy zone, sampling was conducted in the C pit (natural conditions) and F pit (artificial spraying conditions) in field test sites. The three kinds of radionuclides, 85Sr, 13 4Cs and 60 Co, were homogeneously mixed with loess and made into a tracer source, which was buried in the center of the bottom of pit, 1m from the ground surface. 6 cm. The samples were disassembled at 783d (F pit) and 1072d (C pit) respectively after the source layer was buried. Use specially made sampling positioning ring, stratified, sub-ring sampling. Vertical stratification, each layer thickness 1cm; horizontal direction of the ring, the ring diameter of 3 ~ 2 7cm, divided into 9 sizes. Two soil samples were collected from C and F pit, respectively. The activity of 85Sr, 13 4Cs and 60 Co in soil samples was measured by Na I (Tl) γ spectrometer, and the specific activity distribution curves of three nuclides in two wells were obtained. The results showed that the vertical migration distances of 13 4Cs and 60 Co in the two test pits were less than 1 cm, but a small part of the migration distance was larger. However, the specific activity peak of 85Sr was higher in artificial spray conditions The F-pit of 1.5 cm / d of leaching strength migrated downward about 13 cm. In natural conditions, the specific activity peak remained at the source layer of the tracer, but broadened significantly in the upper and lower directions. In addition, it was also found that there were also three species of radionuclides in the horizontal direction at 11.3 cm (F pit) and 12.8 cm (C pit)