Detection of heavy metal and hydrocarbon contamination using a miniature resistivity probe

The usefulness of the electrical resistivity method for characterization of contaminated sites has been studied in many ways. The most commonly used device is a cone penetrometer that utilizes two or four electrodes to measure electrical resistivity (or conductivity) during a cone penetration test (CPT) along a vertical or horizontal alignment. This paper introduces a new miniature resistivity probe (MRP) that can potentially be deployed from a sampling platform to detect contaminant plumes prior to collecting soil samples. Following bench-scale tests aimed at quantifying the sensitivity of the MRP to various operating and environmental parameters, the response of the MRP in sandy soil containing various concentrations of four heavy metals (Cu, Zn, Pb and Ni) and two hydrocarbons (phenol and gasoline) is evaluated. The test data revealed that the MRP has the potential to serve as an indexing tool for rapidly delineating contaminant plumes where heavy metals are present. The results for hydrocarbons were less conclusive, ranging from moderate ability to differentiate contaminated and non-contaminated soils for phenol to poor differentiation ability for gasoline.