Interactive Roles of Microbial and Spartina Populations in Mercury Methylation Processes in Bioremediation of Contaminated Sediments in Salt-Marsh Systems

EPA Grant Number: R825513C025
Subproject: this is subproject number 025 , established and managed by the Center Director under grant R825513
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: HSRC (1989) - South and Southwest HSRC
Center Director: Reible, Danny D.
Title: Interactive Roles of Microbial and Spartina Populations in Mercury Methylation Processes in Bioremediation of Contaminated Sediments in Salt-Marsh Systems
Investigators: Saunders, F. Michael , Frischer, Marc E , King, J. , Kostka, J.
Institution: Georgia Institute of Technology
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 1998 through January 1, 2001
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (1989) RFA Text |  Recipients Lists
Research Category: Hazardous Substance Research Centers , Land and Waste Management


The goal of the project is remediation of mercury-contaminated sediments is being examined to establish the coupled roles arid effects of Spartina, microbial activity and sulfate reducing bacteria (SRB) on mercury methylation in saltmarsh sediments. The fundamental conceptual model (see Figure 1) is that the incidence of mercury methylation is biochemically driven by sulfate-reducing bacteria (SRB) in the top layers of sediments. Furthermore in Spartina systems the production of methyl mercury is potentially lowered in the root zones or altered by biologically mediated demethylation of methylmercury in marsh sediments by the microbial community. Mercury toxicity and availability in the biological food chain is driven by methylmercury and its production is controlled by the net rate of microbial formation and removal within sediments.

The growth of Spartina and the associated injection of root-zone organic exudates and molecular oxygen into microbially active sediments influence sulfate reduction, mercury methylation and demethylation processes. Hence the bioavailability and ultimately the risk associated with mercury contamination in saltmarsh sediments is related to presence and growth of Spartina. Thus, understanding the relationships among sulfate reducing bacteria (SRB), demethylating processes, Spartina and sediment-based mercury will be useful for assessing sediment-quality and developing and assessing in-situ remediation strategies and methods for risk assessment.


The research plan for the current growth season (March '00 - February '01 include an enhanced focus on methylation and demethylation processes in sediments and pursuit of the effects of Spartina on the stabilization of mercury-contaminated sediments. The earlier research (year 01) focused on assessment of the biogeochemical properties of sediments has been reduced to focus on critical parameters directly linked to mercury availability and sulfate reducing populations. Earlier work in this area over the initial 18 months of the project clearly indicated the full equilibration of the sediments and the relevance of the current research to sediments systems in natural saltmarshes.

As described in our initial work plan, mercury demethylation rates will be determined in sediments by incubation with methylmercury using g-level injections of methylmercury in 1-cm, sediment-core lifts and in homogenized slurries from sediment cores using an incubation time of 12 hr in both systems. Demethylation rates will be determined by the loss of methylmercury after incubation. Methylmercury will be determined by distillation, derivatization, chromatographic separation and thermal decomposition using a Tekron 2500 CVAFS (Smith, 1993), as with.all current measurements. Recent improvements in the isolation of methylmercury from sediment and water involve distillation into a Teflon collection vessel with detection limits for methylmercury using this method of 2 ng/L for porewaters and 0.01 g/kg in sediments in SkIO laboratories.

Publications and Presentations:

Publications have been submitted on this subproject: View all 4 publications for this subprojectView all 392 publications for this center

Journal Articles:

Journal Articles have been submitted on this subproject: View all 2 journal articles for this subprojectView all 106 journal articles for this center

Supplemental Keywords:

methylmercury, mercury toxicity, and demethylation., RFA, Scientific Discipline, Waste, Water, Chemical Engineering, Contaminated Sediments, Environmental Chemistry, Analytical Chemistry, Hazardous Waste, Bioremediation, Ecology and Ecosystems, Hazardous, Environmental Engineering, Mercury, hazardous waste management, hazardous waste treatment, risk assessment, sediment treatment, environmental technology, microbial degradation, decontamination of soil and water, soil and groundwater remediation, biodegradation, risk management, contaminated sediment, decontamination of soil, slurry reactors, Spartina, chemical contaminants, microbes, contaminated soil, contaminants in soil, remediation, bioremediation of soils, methyl mercury, biotransformation, technology transfer, extraction of metals, anaerobic biotransformation, waste mixtures, CERCLA, contaminated soils

Progress and Final Reports:

  • 1998
  • 1999
  • Final Report

  • Main Center Abstract and Reports:

    R825513    HSRC (1989) - South and Southwest HSRC

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R825513C001 Sediment Resuspension and Contaminant Transport in an Estuary.
    R825513C002 Contaminant Transport Across Cohesive Sediment Interfaces.
    R825513C003 Mobilization and Fate of Inorganic Contaminant due to Resuspension of Cohesive Sediment.
    R825513C004 Source Identification, Transformation, and Transport Processes of N-, O- and S- Containing Organic Chemicals in Wetland and Upland Sediments.
    R825513C005 Mobility and Transport of Radium from Sediment and Waste Pits.
    R825513C006 Anaerobic Biodegradation of 2,4,6-Trinitrotoluene and Other Nitroaromatic Compounds by Clostridium Acetobutylicum.
    R825513C007 Investigation on the Fate and Biotransformation of Hexachlorobutadiene and Chlorobenzenes in a Sediment-Water Estuarine System
    R825513C008 An Investigation of Chemical Transport from Contaminated Sediments through Porous Containment Structures
    R825513C009 Evaluation of Placement and Effectiveness of Sediment Caps
    R825513C010 Coupled Biological and Physicochemical Bed-Sediment Processes
    R825513C011 Pollutant Fluxes to Aquatic Systems via Coupled Biological and Physicochemical Bed-Sediment Processes
    R825513C012 Controls on Metals Partitioning in Contaminated Sediments
    R825513C013 Phytoremediation of TNT Contaminated Soil and Groundwaters
    R825513C014 Sediment-Based Remediation of Hazardous Substances at a Contaminated Military Base
    R825513C015 Effect of Natural Dynamic Changes on Pollutant-Sediment Interaction
    R825513C016 Desorption of Nonpolar Organic Pollutants from Historically Contaminated Sediments and Dredged Materials
    R825513C017 Modeling Air Emissions of Organic Compounds from Contaminated Sediments and Dredged Materials title change in last year to "Long-term Release of Pollutants from Contaminated Sediment Dredged Material"
    R825513C018 Development of an Integrated Optic Interferometer for In-Situ Monitoring of Volatile Hydrocarbons
    R825513C019 Bioremediation of Contaminated Sediments and Dredged Material
    R825513C020 Bioremediation of Sediments Contaminated with Polyaromatic Hydrocarbons
    R825513C021 Role of Particles in Mobilizing Hazardous Chemicals in Urban Runoff
    R825513C022 Particle Transport and Deposit Morphology at the Sediment/Water Interface
    R825513C023 Uptake of Metal Ions from Aqueous Solutions by Sediments
    R825513C024 Bioavailability of Desorption Resistant Hydrocarbons in Sediment-Water Systems.
    R825513C025 Interactive Roles of Microbial and Spartina Populations in Mercury Methylation Processes in Bioremediation of Contaminated Sediments in Salt-Marsh Systems
    R825513C026 Evaluation of Physical-Chemical Methods for Rapid Assessment of the Bioavailability of Moderately Polar Compounds in Sediments
    R825513C027 Freshwater Bioturbators in Riverine Sediments as Enhancers of Contaminant Release
    R825513C028 Characterization of Laguna Madre Contaminated Sediments.
    R825513C029 The Role of Competitive Adsorption of Suspended Sediments in Determining Partitioning and Colloidal Stability.
    R825513C030 Remediation of TNT-Contaminated Soil by Cyanobacterial Mat.
    R825513C031 Experimental and Detailed Mathematical Modeling of Diffusion of Contaminants in Fluids
    R825513C033 Application of Biotechnology in Bioremediation of Contaminated Sediments
    R825513C034 Characterization of PAH's Degrading Bacteria in Coastal Sediments
    R825513C035 Dynamic Aspects of Metal Speciation in the Miami River Sediments in Relation to Particle Size Distribution of Chemical Heterogeneity