137Cs示踪技术在土壤侵蚀估算中的应用研究进展

137Cs示踪技术目前已被广泛用于长期的土壤侵蚀(水蚀)估算。该技术要解决的两个关键问题是土壤137Cs基准值的确定,以及土壤的137Cs损失量与土壤侵蚀量之间的定量模型的建立。对现有的主要的定量模型进行了简述,并提出了各自的局限性。这些模型可分为经验模型和理论模型两大类,其中以理论模型中的质量平衡模型较为成熟,综合考虑了较多的侵蚀因子,如137Cs年沉降分量、土壤颗粒粒径分布差异、地表富集作用、耕作土壤在耕作活动前新沉降137Cs的侵蚀损失等。对现有模型的改进也进行了探讨,并提出了今后的一些研究重点。

REVIEW OF PROGRESSES IN APPLICATION OF 137Cs TRACER TECHNIQUE TO THE ESTIMATE OF SOIL EROSION

The 137 Cs tracer technique has been widely used in the estimate of water induced soil erosion rate representing a long term. There are two key problems calling for scientific solutions to practical utilization of this technique. One is the determination of reference value of 137 Cs content of soil having experienced neither erosion nor deposition, and the other is the establishment of the quantitative model between the amount of 137 Cs lost from the soil profile and the rate of soil loss. The primary existing quantitative model was reviewed in this paper, and their limitations were also revealed. These models fell into two categories, namely, empirical model and theoretical model, among which the mass balance models are relatively reliable because they involved considerations of many factors related to the soil erosion process, such as annual fractions of 137 Cs fallout input, the grain size selectivity associated with soil erosion and sediment transport processes, surface enrichment, 137 Cs loss due to soil erosion prior to the tillage operation, and etc. The needs of some further improvements of existing models and some additional intensive works were also suggested in this paper.