电阻率成像法在非均质土壤特性监测及土壤水文过程研究中的应用

Soil spatial heterogeneity and the dependency of soil properties and hydrological processes on scale caused by it is one of the most important challenges faced by soil hydrology. Lacking technologies concerning multi-scale monitoring in situ is the bottleneck to resolve such scale problems. Electrical resistivity tomography(ERT), one kind of geophysical technology, can provide multi-scale, undisturbed, and even time-lapse monitoring in situ. Studies on soil hydrological processes in vadose zone based on ERT have been one of the hottest spots in soil physics in recent years. According to the unsolved problems occurring in monitoring sources of variations in vadose zone and inversing soil resistivity using ERT, this project will be conducted to systemically study the influences of other soil properties on soil resistivity, configuration of ERT monitoring and approaches to invert soil resistivity. On of the target is to find when and how the ERT can be used to obtain soil properties and their spatial heterogeneity, and which configuration of monitoring and inversing method are the optimum to accurately detect some different sources of soil variations. Furthermore, methods based on monitoring by ERT, soil physical principles and hydrogeophysical inversions will be also studied to characterize soil structure and determine soil hydraulic properties, as well as their spatial heterogeneity at multi-scale. Finally, advantage of ERT will be used to discover the rule controlling the changes of soil properties and hydrological processes with monitoring scale or effective scale, and the possible approaches to convert scales of soil property parameters and soil hydrological models.

土壤空间异质性，及其导致的土壤特性和土壤水文过程的尺度依赖性问题是土壤水文学当前面临的最为重要的挑战之一，而多尺度观测技术却是制约尺度问题解决的瓶颈。以电阻率成像技术为代表的地球物理方法则提供了这样一种多尺度无损连续监测方法，基于电阻率成像法的非饱和带水文过程研究已经成为近年研究的热点问题之一。本项目针对目前非饱和带电阻率成像法在变异源监测、电阻率反演过程中存在的一些问题，拟通过对土壤电阻率与其他土壤特性的关系，电阻率成像法监测参数配置，视电阻率反演方法的研究，明确电阻率成像法在各种情况下监测土壤特性异质性的可靠性，提出针对各类土壤变异源的最优电阻率成像法监测参数配置和反演方法；并据此发展田间多尺度的土壤结构和土壤水力特性参数的确定方法，揭示土壤特性和土壤水文过程的空间异质性及其尺度依赖性规律，建立土壤特性参数及土壤水文过程模型的尺度转换方法。

摘要：土壤空间异质性及其导致的土壤特性和土壤水文过程的尺度依赖性问题是当前土壤水文学面临的最为主要的挑战之一。多尺度监测技术以及田间尺度土壤水力特性参数预测理论的缺乏是制约这一问题解决的瓶颈。以电阻率成像法（ERT）为代表的地球物理学方法近些年开始应用到非饱和带研究中来，为土壤水文过程监测提供了一种多尺度无损连续监测的手段，但其监测和反演中存在的一些问题有待解决，其监测结果多尺度的特征也未得到有效利用。针对这些问题，本项目开展了室内外试验，结合理论推导和数值模拟系统研究了田间尺度土壤水文过程的电阻率成像方法，以及土壤水力特性参数测定方法，取得了如下一些成果：（1）建立了几种典型土壤的电阻率与土壤水分和土壤水力特性指标之间的关系；（2）完善了层状土壤在入渗和排水过程中利用ERT技术时间连续性监测和反演土壤水分的方法；（3）发展了新的入渗问题简单解析解，拓展了Green-Ampt入渗模型，极大地改进了Green-Ampt入渗模型参数和土壤水力特性之间的定量关系；（4）建立了室内外通过简单入渗试验获取多尺度土壤水力特性参数的理论基础；（5）提出了预测田间尺度地下水补给过程的研究方法。本项目的研究结果对于拓展田间尺度土壤水文过程监测手段，获取田间尺度土壤水力特性参数，揭示土壤水文过程的尺度依赖性规律具有重要参考价值。