| Abstract: | Successful in situ groundwater remediation relies on the adequate distribution of treatment materials within the subsurface. Zero‐valent iron (ZVI) is widely used for the remediation of soils contaminated with chlorinated organic compounds. Because ZVI is a solid, various techniques are used to distribute ZVI in the subsurface; however, a major uncertainty in this process involves determining the distribution of the iron during emplacement. A method of mapping the distribution of ferromagnetic material such as ZVI is by magnetic susceptibility (MS), a novel approach that is highly sensitive, quantitative, objective, and easily applied in field. The method has been tested in the laboratory on synthetic cores containing EHC®, an organic amendment containing 40 to 50% ZVI, using an MS meter with two types of sensors (loop and handheld). Both sensors have high sensitivity (e.g., 1% disseminated EHC is easily detected), whereas the hand‐held sensor has greater spatial resolution (e.g., differences are notable on a scale of 1 cm). Following the laboratory studies, the handheld instrument was used to perform field measurements for multiple pilot studies and a full‐scale application of EHC using various delivery methods (pneumatic fracturing, hydraulic fracturing, and direct injection) to construct a biobarrier at a field remedial site. The MS method has proven invaluable in quantifying amendment distribution and ensuring appropriate application of this remedial technology. |
