Complex Electrical Resistivity from Monitoring DNAPL Contamination

Brown, Stephen R.

United States. Department of Energy. Office of Scientific and Technical Information.

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

DOI  :  10.2172/831190
RP-ID  :  EMSP-70012--2003
RP-ID  :  FG07-99ER15005
RP-ID  :  831190

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. According to Olhoeft, 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 relative phase (or time delay) 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, seldom have been successful. Encouraged by the aforementioned laboratory results we had 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 and chemical mechanisms, and then apply these observations to develop field techniques to monitor the remediation of organic pollutants. Research Progress