6533b7cffe1ef96bd1258615

RESEARCH PRODUCT

Sensitivity Analysis Of Multi-Electrode Arrays For Characterizing The Non-Saturated Zone In Groundwater Vulnerability Assessment

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The near-surface environment acts as a filter and buffer for contaminants introduced from the surface by anthropogenic activities. For this reason there is a great need to improve our understanding of the shallow subsurface taking into account the increasing demand for vulnerability maps which illustrates the exposure of aquifers against pollution. These maps are designed to show areas of greatest potential for groundwater contamination on the basis of local subsurface conditions. A shallow, unconfined sand-and-gravel aquifer is highly vulnerable to pollutants because rapid recharge gives little time to contaminants to degrade naturally or be adsorbed before reaching the aquifer. Conversely, a deep, confined aquifer has a very low vulnerability. Infiltrating recharge could take years to reach the aquifer, allowing time for contaminants to abate or degrade. Therefore, parameters affecting vulnerability are mainly the permeability and the thickness of each protective layer. For unconsolidated sediments, the permeability is strongly related to the clay content, which can be deduced from indirect resistivity methods, like electrical resistivity tomography. Such geophysical method can be of great help in groundwater vulnerability studies because they do not alter the structure of the soil. In this paper the sensibility of different geoelectrical multi-electrode arrays for assessing groundwater vulnerability is tested.