1 / 12

NIEHS R01ES024344 2014-2018

This project focuses on establishing indicators for methylmercury production potential in contaminated sediments and predicting methylation potential by considering factors such as productivity of methylating microorganisms and bioavailability of mercury. The study explores various geochemical forms of mercury in sediments and identifies microorganisms capable of methylating mercury. The project aims to evaluate mercury methylation potential using sediment-water microcosms from Superfund sites and assess the effectiveness of in-situ remediation approaches. The research involves measuring methylating microbe activity, hgcAB gene abundance, microbial diversity, and controls on methylation potential. Various sediment amendments are tested, including activated carbon, clay minerals, and ferrous iron, to mitigate mercury bioavailability. The project also delves into quantifying mercury bioavailability and evaluating the effectiveness of remediation strategies through data analysis and field samples from different sites.

jkennon
Download Presentation

NIEHS R01ES024344 2014-2018

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Biogeochemical Framework to Evaluate Mercury Methylation Potential During in-situ Remediation of Contaminated Sediments Heileen Hsu-Kim, Marc Deshusses Duke University Dwayne Elias Oak Ridge National Lab NIEHS R01ES024344 2014-2018

  2. Project team Duke University Helen Hsu-Kim (PI) – Aquatic Geochemistry Marc Deshusses (Co-PI) – Bioremediation Oak Ridge National Lab Dwayne Elias (Co-PI) – Microbial Ecology Other Collaborators Steven Brown,Ph.D., Dow Chemical, Berry’s Creek Study Group

  3. Challenges of the mercury problem: • Many sources to biosphere • Long range transport • Food web accumulation • Mechanisms of MeHg production Selin, 2009, Annu. Rev. Environ. Resour. Objective: To establish biogeochemical indicators for methylmercury production potential

  4. Factors contributing towards mercury methylation potential Framework to predict methylation potential Productivity of methylating microorganisms Bioavailability of Hg ? ?

  5. Geochemical Forms of Mercury in Sediments HgHxS2x-2 Hg-thiol Hg-DOM Aggregated or micro-crystalline HgS(s) Amorphous or crystalline HgS nanoparticles DOM-capped polynuclear HgS clusters Dissolved Hg(II) complexes High methylation potential Low methylation potential

  6. Microorganisms that Methylate Mercury Gilmour et al., ES&T, 2013 Firmicutes, Clostridia • Obligate anaerobes • Phylogenically diverse • hgcAB: two gene cluster Deltaproteobacteria ARCHAEA Euryarchaeota

  7. Biomethylation in Sediment Slurry Microcosms Saline water Freshwater Ambient Hg: 2 nmol g-1 Spike Hg: 2 nmol g-1 [SO42-]0 = 15 mM [SO42-]0 < 0.07 mM dissolved Hg+sulfide dissolved Hg+sulfide nano-HgS nano-HgS microcrystalline HgS microcrystalline HgS Bioavailability-limited methylation Productivity-limited methylation Zhang et al., ES&T, 2014

  8. Bioavailability vs. Productivity Mixed microbe community enriched from sediments Dissolved Hg added Nano HgS added C-substrate for growth Threshold? Kucharzyk et al., ICMGP, 2013

  9. Project Objectives: • To establish biogeochemical indicators for methylmercury production potential • To test the effectiveness of in-situ remediation Sediment-water microcosms with samples from Superfund site Measurements of Methylation Potential Site Characterization and Remediation • Aim 1: Activity of methylating microbes • hgcAB gene abundance/expression • Microbial diversity • Aim 3: Delineation of the controls on methylation potential • Limited by microbial activity • Limited by bioavailability • Aim 4: Effects of sediment amendments • Activated carbon • Clay mineral particles • Ferrous iron (FeCl2) • Aim 2: Hg bioavailability • Size fractionation, solid-water partitioning of Hg • Thiol-extraction potential • Passive sampler with thiolated resin

  10. Activity of Methylating Microbes Amino acid sequence alignments for hgcAB for all predicted Hg-methylating organisms Design schematic for PCR, qPCR and RT-qPCR primers. Parks et al., Science, 2013 Gilmour et al., ES&T, 2013

  11. Quantification of Hg bioavailability Thiol-based selective extraction microbial culture: D. priopionicus 1pr3 dissolved Hg+sulfide nano-HgS bulk-scale HgS Zhang et al., ES&T, 2012

  12. Evaluation of Hg methylation potential in sediments Anaerobic sediment-water microcosms Data Analysis: Calibration of measurement methods • Major experimental variables: • Sediment origin • Type of Hg added (dissolved, nanoHgS, Hg-FeS) differentiated by Hg isotope • Measurements of methylation potential: • MeHg concentration or net production rate • Gene abundance & expression • Hg bioavailability (thiol selective extraction) MeHg production rate bioavailable [Hg] Field samples of benthic sediments • (Oak Ridge, TN; Berry’s Creek Study Area; other sites?) • Range of characteristics: • Salinity • Organic Carbon • MeHg concentration (relative to total Hg) hgcAB abundance or expression Assess the effectiveness of remediation

More Related