You are here:
REACTIVITY OF CHEMICAL REDUCTANTS AS A FUNCTION OF REDOX ZONATION
Citation:
Weber, E J., J F. Kenneke, J W. Washington, AND L. A. Hoferkamp. REACTIVITY OF CHEMICAL REDUCTANTS AS A FUNCTION OF REDOX ZONATION. Presented at Gordon Research Conference 2000 on Environmental Sciences, Plymouth, NH, June 25-30, 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 incorporation of reductive transformations into fate models continues to be a challenging problem. The occurrence of chemical reductants in anaerobic sediments and aquifers is a result of the reduction of inorganic, electron acceptors coupled to the microbial oxidation of organic matter. Depending on the distribution of thermodynamic conditions, a sequence of redox zones can develop that are characterized by the respective dominant terminal electron accepting process (i.e., nitrate-, manganese-, iron-, sulfate-reducing and methanogenic). It is logical that the dominant chemical reductants in subsurface environments will vary as a function of the redox zonation. To understand this relationship, the reaction kinetics for a series of probe molecules (halogenated methanes and nitroaromatics) have been measured in sediments for which redox conditions have been well characterized. Redox characterization has included quantifying the major redox-active species in sediment pore waters (NO3(-), Mn2+, Fe2+, SO4(2-) and H2) and the use of sequential extractions to determine the major pools of FE(II) and FE(III) associated with the solid phase of the sediments. The results of these studies will be presented showing the relationship between the reaction kinetics of the probe molecules with the redox zonation of natural sediments.