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COMPARISON OF HYDROGEN CONCENTRATIONS IN PCE-DEHALOGENATING AND SULFATE-REDUCING ESTUARINE SEDIMENTS
Citation:
Mazur, C S. AND W J. Jones. COMPARISON OF HYDROGEN CONCENTRATIONS IN PCE-DEHALOGENATING AND SULFATE-REDUCING ESTUARINE SEDIMENTS. Presented at 220th American Chemical Society National Meeting, Washington, DC, August 20-24, 2000.
Impact/Purpose:
Elucidate and model the underlying processes (physical, chemical, enzymatic, biological, and geochemical) that describe the species-specific transformation and transport of organic contaminants and nutrients in environmental and biological systems. Develop and integrate chemical behavior parameterization models (e.g., SPARC), chemical-process models, and ecosystem-characterization models into reactive-transport models.
Description:
The primary transformation pathway for PCE in anoxic environments is through sequential reductive dehalogenation, and information concerning dehalogenation processes that occur in environments containing alternative electron acceptors (sulfate) is limited. Hydrogen is postulated as a key electron donor during PCE transformation, and the "hydrogen threshold"concept suggests that microorganisms that utilize an energetically more favorable electron acceptor will maintain a lower hydrogen threshold. We compared the hydrogen concentrations in unamended and PCE-amended estuarine sediment slurries. A significantly lower hydrogen concentration (0.42-0.47 nM) was observed and maintained in PCE-amended sediment microcosms compared to sulfate-reducing sediments (0.6-0.7 nM). Our findings provide evidence that a lower hydrogen threshold exists in anoxic estuarine sediment slurries with PCE serving as a terminal electron acceptor compared to sediment slurries in which sulfate-reduction is the predominant electron accepting process.