High-resolution non-invasive mapping of vertical heterogeneity in sandy soils of the Oak Openings Region using electromagnetic imaging and ground penetrating radar

Abstract

Abstract 10 Traditional soil investigation methods involve laboratory analysis on soil cores or direct 11 measurements of soil properties with in-situ sensors. These methods are, however, destructive, 12 labour-intensive, and ineffective in capturing the spatial variation of soil properties. Geophysical 13 methods provide a non-invasive approach to rapidly characterize soil properties distribution. Gaps, 14 however, exist in the use of non-contact-based geophysical methods such as ground penetrating 15 radar (GPR) and electromagnetic imaging (EMI) for characterizing the vertical variation of soil 16 properties. This study assesses the use of EMI and GPR for quantifying the vertical variation of 17 soil moisture content (SMC), soil organic matter (SOM), and soil texture. Co-located EMI and 18 GPR surveys were conducted along 12 transects at the Stranahan Arboretum research site in 19 Toledo, Ohio. Soil samples collected from nine locations along the transects were segmented into 20 63 subsamples and analysed for SMC, SOM, and soil texture. Apparent electrical conductivities 21 (ECa) from EMI were inverted to obtain lateral and vertical variations of soil electrical conductivity 22 (EC), which captures three major lithostratigraphic units (sand, silty loam, and silt) found in soil 23 cores within the top 2.0 m. Soil EC correlates with SMC, SOM and soil texture, with coefficient 24 of determination (R2) ranging from 59-91%. The GPR radargrams show reflectors consistent in 25 delineating sandy and silty clay soils but unable to distinguish between sand and silt. These results 26 validate the effectiveness of using EMI and GPR to delineate vertical variation of soil properties 27 and characterize stratigraphic heterogeneity, expanding the possibilities for non-invasive three28 dimensional (3D) soil properties mapping