A Laboratory Study Of The Complex Electrical Resistivity Response Of Soils

There is an increasing need for new non-invasive geophysical techniques to locate DNAPLs in the<br>subsurface. G. Olhoeft and colleagues have published several reports which indicate that organic solvents,<br>notably toluene, PCE, and TCE, residing in clay-bearing soils have distinctive electrical signatures. These<br>results suggest a new measurement technique for remote characterization of DNAPL pollution.<br>As with any new research result we note the importance of reproducing the work of previous researchers<br>to ensure that any effects observed are due to the physical phenomena occurring in the specimen<br>and not due to the particular experimental apparatus or method used. To this end, we independently<br>designed and built a laboratory system for the measurement of the complex electrical resistivity properties<br>of contaminated soil. After careful characterization and calibration of our equipment, we attempted<br>numerous times to reproduce the seminal results of Olhoeft and Sadowski on the response of toluenecontaminated<br>clay-rich samples. While we observe similar responses to theirs for plain clays with brine,<br>the addition of toluene does not produce the effects they described.<br>Our results indicate, at best, a low sensitivity of the complex electrical resistivity method to organic<br>contamination in rocks and soils.