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Abstract Title: Evaluation of Manganese Oxide Amendments for Mercury Remediation in Contaminated Aquatic Sediments
Presenter Name: Mark Seelos
Company/Institution: Valley Water
Session: Mercury Treatment / Abatement
Day and Session: Monday 25th July - Session One
Start Time: 0600 UTC
Co-Authors: Mark Seelos

Abstract Information :

Aquatic sediments are important sources of toxic methylmercury (MeHg) to the environment because they support anaerobic bacteria that methylate inorganic mercury (Hg). Common Hg remediation strategies such as sediment removal or capping can be prohibitively expensive or impractical when compared to in situ treatment methods designed to disfavor Hg methylation and increase sorption of MeHg to solids. Using profundal sediments from a Hg-contaminated reservoir, we assessed the effectiveness of Mn(IV) oxide (MnOx) amendments in decreasing porewater and sediment Hg and MeHg concentrations relative to sediments treated with granular activated carbon (AC) and unamended controls. We conducted two sediment slurry incubation experiments (0?20 days and 0?5 days) using sediments amended with MnOx, AC, or a mixture of the two. X-ray absorption spectroscopy data showed that the MnOx amendments were rapidly reduced to Mn2+ over the course of the incubation. In both experiments, MnOx addition resulted in elevated oxidation?reduction potential and lower MeHg concentrations in porewater relative to unamended controls after 2?3 days. The MnOx amendments decreased porewater MeHg with similar or greater effectiveness as AC. However, sediments amended with MnOx released inorganic Hg into porewater in some experiments. Coamendment of MnOx with sorbents could curtail diffusion of MeHg from aquatic sediments and slow MnOx reduction while limiting the release of potentially problematic byproducts such as Mn2+ and Hg(II).

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