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Mercury (Hg) is one of the most pervasive and bio-accumulative metals in the environment. Yet, effective in situ remediation technologies have been lacking. This study investigated the effectiveness of a class of soil-deliverable FeS nanoparticles for in situ immobilization of Hg in two field-contaminated soils from a New Jersey site and one sediment from an Alabama site. The nanoparticles were prepared using sodium carboxymethyl cellulose (CMC) as a stabilizer. Transmission electron microscopy measurements revealed a particle size of 34.3 ± 8.3 nm (standard deviation), whereas dynamic light scattering gave a hydrodynamic diameter of 222.5 ± 3.2 nm. Batch tests showed that at an FeS-to-Hg molar ratio of 28:1-118:1, the nanoparticles reduced water-leachable Hg by 79%-96% and the TCLP (toxicity characteristic leaching procedure) based leachability by 26%-96%. Column breakthrough tests indicated that the nanoparticles were deliverable in the sediment/soil columns under moderate injection pressure. However, once the external pressure was removed, the delivered nanoparticles remained virtually mobile under typical groundwater flow conditions. When the Hg-contaminated soil and sediment were treated with 52-95 pore volumes of a 500 mg l(-1) FeS nanoparticle suspension, water-leachable Hg was reduced by 90%-93% and TCLP-leachable Hg was reduced by 65%-91%. The results warrant further field demonstration of this promising in situ remediation technology.

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An extensive network of characterization boreholes was installed as part of Phase I of the Integrated Demonstration Project. These boreholes were used for a variety of purposes including: (1) to characterize the lithology, stratigraphy, microbiology and hydrology of the site; (2) to determine the distribution of contamination prior to the field test; (3) to monitor the pressures and concentrations of dissolved constituents in the groundwater; (4) to monitor the pressure and concentration of gases in the vadose zone; (5) to facilitate geophysical measurements.Several types of information are presented and discussed in this report, including: a general site description, stratigraphy, hydrology, type and location of borings, sampling and analysis techniques for groundwater and sediments, distribution of contaminants, and structural and functional characterization of the subsurface microbiological community. The pretest data presented in this report will be compared with data collected during and after the full scale field demonstration to provide a detailed measure of the effects of the in-situ air stripping process.