Session: Innovation in Remediation Strategies & their Impact on Superfund Contaminants:

Streambank soils within the East Fork Poplar Creek (EFPC) watershed have elevated concentrations of mercury (Hg) as a result of historic use and discharge of Hg into the system associated with activities at the Y-12 National Security Complex. Mercury can leach from these soils as a result of water level fluctuations and erosion of stream banks resulting in the soils acting as a source of Hg to the creek. Laboratory experiments were conducted to examine the amount of Hg leaching from two soil samples collected from EFPC and a soil sample collected from Hinds Creek, an uncontaminated creek used as a reference site. For these batch laboratory studies the amount of mercury leaching from the soils when exposed to water from EFPC was examined for two weeks with samples collected every 3-4 days. After two weeks, solid phase sorbents were added to some of the samples and the amount of Hg leaching from the soils with and without sorbent addition was examined for an additional two weeks. The concentration of Hg in the reference soil was 0.027 µg/g and the two soils from EFPC had Hg concentrations approximately 200 and 10,000 times greater than the reference soil. After the two-week leaching period with creek water, the concentration of Hg in the aqueous solution was 5.3 ng/L in the soils from the reference site and approximately 24 ng/L and 440 ng/L in the aqueous phase of the contaminated soil treatments. The solid phase sorbents that were tested included Thiol-SAMMS^®, Organoclay^TM PM-199, Organoclay^TM MRM, SediMite^TM and a biochar. The addition of the sorbent resulted in a decrease in the Hg leaching from the sediment. SediMite^TM provided the greatest reduction in Hg leaching from the soils. In a separate experiment the impact of repeatedly wetting and drying the soil showed that this process increases the leaching of Hg from the soils. Results from this laboratory study will help evaluate the usefulness of solid phase sorbent materials as a remedial option for reducing the amount of Hg leaching from soils into East Fork Polar Creek.

Alexander Johs

Oak Ridge National Laboratory

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