^(137)Cs示踪农耕地土壤侵蚀速率模型的比较研究

THE DISCUSSION ON MODELS FOR ESTIMATINGSOIL EROSION RATES FROM CAESIUM-137MEASUREMENTS ON CULTIVATED LAND

137Cs示踪技术广泛地应用于农耕地土壤侵蚀研究,目前已建立了许多运用137Cs估算土壤侵蚀速率的模型。这些模型主要分为两类:经验模型与理论模型。其中理论模型中的质量平衡模型应用较多。质量平衡模型主要有:Walling模型、张信宝模型、杨浩模型和周维芝模型。重点讨论这4种质量平衡模型的异同。详细阐述了这四种模型的建立过程,并用图形模拟的方法给出各个模型所刻画的土壤侵蚀速率与土壤剖面中137Cs相对损失率的关系。分析表明,尽管各个模型在建立的假设和方法上以及对137Cs沉降过程的处理上存在一定程度的差异,但是各个模型所刻画的土壤侵蚀速率与土壤剖面中137Cs相对损失率的关系实质上都是幂函数的形式,而且这4条曲线的走势基本一致,各自计算的土壤侵蚀速率差异也较小。因此,在利用137Cs技术示踪农耕地土壤侵蚀速率时,这4个模型都可以应用。

Soil erosion on agricultural land has become a global environmental problem and information on rates of soil loss is an important requirement both for quantifying the problem and for developing improved land management and soil conversation practices. The use of fallout ^(137)Cs measurements can overcome many of the difficulties facing traditional approaches to erosion monitoring and provide an effective means for obtaining estimates of soil redistribution rates on cultivated land. 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 that has never experienced erosion and deposition, and the other is the establishment of the quantitative model between the amount of ^(137)Cs loss from the soil profile and the rate of soil erosion. At present, a number of empirical functions and theoretical models have been developed to establish the relationship between the change in the soil ^(137)Cs inventory relative to the local ^(137)Cs fallout input and the rate of soil erosion. They are reviewed and evaluated in this paper. The physically based mass balance models are relatively reliable because they involved considerations of many factors related to the erosion process. The mass balance models include Walling model, Zhang Xinbao.model, Yang Hao.model, and Zhou Weizhi.model. Although they all belong to the mass balance model, they were established by different ways. This paper will mainly discuss the difference and similarity among these four models.