摘要
基于土壤中溶质运移的对流 弥散方程 (CDE)提出了溶质运移参数估计的图解方法。根据土柱溶质运移“穿透曲线”(BTC)数据计算通量浓度随时间变化 (dc/dt)。应用绘图软件 ,例如MicrosoftExcel,绘制出t1 5dc/dt和dc/dt相对于时间的变化曲线。这两条曲线都是单峰曲线 ,并被用于估计CDE中延迟因子(R)和弥散系数 (D0 )。设计算例和穿透实验数据被用于校正图解法估计参数的精度和稳定性。参数估计的稳定性由估计参数对它们平均值的标准差评价 ;参数的估计精度与CXTFIT法和等斜率法比较。结果表明图解法具有较高的精度和较好的稳定性 ,特别是对于运移参数R的估值。图解法是一个确定性方法 ,它具备确定性方法中估计参数唯一性特点 ,克服了统计方法中需要给定参数初值的缺点。因此 ,这个方法是土壤溶质运移参数估计的可选方法之一。
A graphing method is proposed in this paper for estimating parameters of solute transport in soils based on the convection-dispersion equation (CDE). The ratio of flux concentration changing with the time (dc/dt) is obtained on data of breakthrough curves (BTCs) of solute transport in a semi-infinite soil column. Using graphing software, for example, the Microsoft Excel, can draw two curves of t 1.5dc/dt and dc/dt in respect to time. Each curve has a single peak. The two curves are used to estimate the retardation factor (R) and dispersion coefficient (D_0) in the CDE. Hypothetical examples and displacement experimental data of the two soils were used to validate the new graphing method for its accuracy and stability of the estimation of the two parameters. The stability of parameter estimation is evaluated by the standard deviations of estimated parameters against their average value. The accuracy of the new method is assessed by comparing it with other two most used methods that are the CXTFIT and the equal-slope method. The results show that the method high both in accuracy and in stability. The new method is particularly good for estimating parameter R. The method is a deterministic method and it is simple in terms of calculation. It also has the advantages of uniqueness and no initial guess of parameters over the CXTFIT method. The new method provides an alternative approach to estimating parameters of solute transport in soils. It is simple, accurate, stable, and saves time.
出处
《土壤学报》
CAS
CSCD
北大核心
2004年第5期715-720,共6页
Acta Pedologica Sinica
基金
国家自然科学基金项目 (5 98790 2 6)和湖南师范大学重点学科项目资助
