关键词: ¹³⁷Cs活度, 土壤颗粒组成, ¹³⁷Cs再分配, 原生沉积物

Abstract: The world-fallout of caesium-137 (¹³⁷Cs ) associated with the nuclear weapons tests during 1950sand 1970s has provided a valuable man-made tracer for studies of soil erosion and sediment delivery. In the process of ¹³⁷Cs redistribution, the particle size composition is among one of most important factors influencing on the ¹³⁷Cs activity of soil. There is a common and classical theory that the ¹³⁷Cs activity mainly re-lated to the clay content of soil, which depended on what the particle composition of the origin sediment as¹³⁷Cs fallout was. In this study, three mixed samples within.0~30 cm depth are collected from the three soil types in the Gonghe Basin, Qinghai Province, China, and sorted by artificially sieving into different particle size components which ¹³⁷Cs activity measured respectively. From this preliminary experiment, the¹³⁷Cs activity of sandy soil decreases exponentially with the mean diameter of grain-size (M_z), and the 0.1~0.01 mm component has the most outstanding affect on ¹³⁷Cs activity. But as to the loam soil, the ¹³⁷Cs activity is mainly related to the coarse silt content(0.05 ~0.01 mm) of soil, and independent on the physical clay content (<0.01 mm). It means that the ¹³⁷Cs activity of soil is directly correlative to the particle characteristics and grain-size of origin sediment of ¹³⁷Cs fallout. Once the ¹³⁷Cs is absorbed by the particle with certain components of origin sediment, it cannot be exchanged by other components even clay in the processes of soil and ¹³⁷Cs redistribution.

Key words: ¹³⁷Cs activity, particle composition, ¹³⁷Cs redistribution, origion sediment of ¹³⁷Cs fallout