Geophysical methods reveal the soil architecture and subsurface
stratigraphic heterogeneities across land-lake interfaces along Lake
Erie
Abstract
The land-lake interface is a unique zone where terrestrial and aquatic
ecosystems meet, forming part of the Earth’s most geochemically and
biologically active zones. The unique characteristics of this interface
are yet to be properly understood due to the inherently high
spatiotemporal variability of subsurface properties, which are difficult
to capture with the traditional soil sampling methods. Geophysical
methods offer non-invasive techniques to capture variabilities in soil
properties at a high resolution across various spatiotemporal scales. We
combined electromagnetic induction (EMI), electrical resistivity
tomography (ERT), and ground penetrating radar (GPR) with data from soil
cores and in-situ sensors to investigate hydrostratigraphic
heterogeneities across land-lake interfaces along the western basin of
Lake Erie. Our Apparent electrical conductivity (ECa) maps matched soil
maps from a public database with the hydric soil units delineated as
high conductivity zones (ECa > 40 mS/m) and also detected
additional soil units that were missed in the traditional soil maps.
This implies that electromagnetic induction (EMI) could be relied upon
for non-invasive characterization of soils in sampling-restricted sites
where only non-invasive measurements are feasible. Results from ERT and
GPR are consistent with the surficial geology of the study area and
revealed variation in the vertical silty-clay and till sequence down to
3.5 m depth. These results indicate that multiple geophysical methods
can be used to extrapolate soil properties and map stratigraphic
structures at land-lake interfaces, thereby providing the missing
information required to improve the earth system model (ESM) of coastal
interfaces.