Complex Electrical Resistivity for Monitoring DNAPL Contamination

Brown, Stephen R.

New England Research, Inc.

关键词: Removal;    Sample Holders;    Breakdown;    Monitoring;    Organic Solvents;   

DOI  :  10.2172/833488
RP-ID  :  EMSP-70012--2001
RP-ID  :  FG07-99ER15005
RP-ID  :  833488

美国|英语

来源: UNT Digital Library

【 摘 要 】

Nearly all Department of Energy (DOE) facilities have landfills and buried waste areas. Of the various contaminants present at these sites, dense non-aqueous phase liquids (DNAPL) are particularly hard to locate and remove. There is an increasing need for external or non-invasive sensing techniques to locate DNAPLs in the subsurface and to track their spread and monitor their breakdown or removal by natural or engineered means. G. Olhoeft and colleagues have published several reports based on laboratory studies indicating that strong electrical signatures are produced when organic solvents, notably toluene, PCE, and TCE, reside in clay-bearing soils. These electrical signatures are apparently characteristic of and unique to the particular organic solvent involved. The experiments are performed by packing the contaminated soil in a sample holder and a 4-electrode complex electrical resistivity measurement is made, where two of the electrodes are used to impose a sinusoidal electric current and the remaining two electrodes are used to sense the response voltage of the specimen. The phase (or time) lag between the source and the response signals at low excitation frequencies is a particularly sensitive measure of electrochemical processes occurring within the specimen. This suggests the basis of an ideal new measurement technique for geophysical characterization of NAPL pollution. Despite the promising laboratory results, attempts to measure these effects in the field for characterizing polluted sites, including studies supported by DOE funding, have been seldom successful. Based on this promising previous work we have proposed to bring the field measurement of complex resistivity as a means of pollution characterization from the conceptual stage to practice. For this purpose we intend to document the detectability of clay-organic interactions with geophysical measurements in the laboratory, develop further understanding of the underlying physical a nd chemical mechanisms, and then apply these observations to develop field techniques to monitor the remediation of organic pollutants.