Evaluation of electrical resistivity tomography (ERT) for mapping the soil\u2013rock interface in karstic environments

Qinbo Cheng,Min Tao,Andrew Binley,Xi Chen

doi:10.1007/s12665-019-8440-8

Abstract

Rocky desertification is a significant threat in the karst regions of southwest China. Studies of soil distribution can contribute to protecting and recovering the fragile karst ecosystem that is prevalent in this region. With an underlying aim of being able to assess soil stocks in karstic environments, this study evaluates the use of electrical resistivity tomography (ERT) for delineating the soil–rock interface. Using a synthetic model (that recognizes the three-dimensional nature of the subsurface), experiments are performed to assess the impact of measurement errors and measurement configuration on recovery of the interface. The inverted results show that the accuracy of the delineation of the soil–rock interface decreases with the increase of measurement error and dipole spacing. The results also show the importance of reliable estimation of measurement errors. Field-based applications of ERT at five exposed profiles in southwest China are also reported. For the field data, three-dimensional modelling was necessary to account for the exposed face. The field experiments show that ERT can be effective at delineating the interface between soil and bedrock, but resolution can be limited due to the scale of features or lack of contrast between soil and bedrock. The method shows great promise as a means of assessing, in a non-invasive manner, the soil–bedrock interface, and, perhaps, more significantly, quantifying estimates of total soil stocks, as we seek to quantify the vulnerability or resilience of this important landscape to anthropogenic and natural stresses.

Highlights

Soils provide a matrix for vegetation, a supply of minerals and nutrients for plant growth, an essential medium that allows the exchange of water and gases between the surface and subsurface, a significant store of carbon and a habitat for insects and many other organisms (Miller 1953; SchoonoverThis article is a part of Topical Collection in Environmental Earth Sciences on Characterization, Modeling, and Remediation of Karst in a Changing Environment, guest edited by Zexuan Xu, Nicolas Massei, Ingrid Padilla, Andrew Hartmann, and Bill Hu.Karst landforms are formed from the dissolution of soluble rocks, which can lead to physical collapse of bedrock and can often result in the development of the caves, springs, and underground rivers (Sweeting 1995; Goldscheider and Drew 2007)
This study has shown how Electrical resistivity tomography (ERT) can be used effectively to assess the soil–rock interface in karstic environments
The inverted results based on the synthetic data show that the accuracy of the delineation of the soil–rock interface decreases with the increase of measurement error, and dipole spacing

Summary

Introduction

Soils provide a matrix for vegetation, a supply of minerals and nutrients for plant growth, an essential medium that allows the exchange of water and gases between the surface and subsurface, a significant store of carbon and a habitat for insects and many other organisms (Miller 1953; SchoonoverThis article is a part of Topical Collection in Environmental Earth Sciences on Characterization, Modeling, and Remediation of Karst in a Changing Environment, guest edited by Zexuan Xu, Nicolas Massei, Ingrid Padilla, Andrew Hartmann, and Bill Hu.Karst landforms are formed from the dissolution of soluble rocks (such as limestone, dolomite, marlstone, and gypsum), which can lead to physical collapse of bedrock (sinkholes) and can often result in the development of the caves, springs, and underground rivers (Sweeting 1995; Goldscheider and Drew 2007). Erosion and suffosion processes (associated with subsidence sinkholes or doline formation via either collapse or subsidence) at, or near, the ground surface can result in complex soil profiles (Fig. 1). The karst region of southwest China is one of the largest contiguous areas of karst globally, and covers 540,000 km (Hollingsworth 2009). In this area, the terrain undulates significantly because of the combination of bedrock dissolution and tectonic processes, enhanced by the warm and moist climate. The production rate of soil is low

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