Mechanisms That Regulate The Intensity Of Oxidation-Reduction In Anaerobic Sediments And Natural Water Systems

Abstract

A literature review and a series of laboratory experiments were conducted to investigate the mechanisms that regulate the intensity of oxidation-reduction in natural environments. Results of the literature review indicated that following depletion of oxygen and nitrate, the highly reduced conditions reached by systems containing substantial amounts of organic matter appear to involve mixed potentials generated by unknown organic oxidation-reduction couples that act in concert with inorganic oxidation-reduction couples. Results of the laboratory studies confirmed that organic oxidation-reduction couples of an unknown nature were exerting a strong influence on Eh. The iron and manganese oxidation-reduction systems were also shown to be affecting Eh, although in a manner consistent with the existence of a mixed potential. Redox potential should only be used as a semiquantitative indicator of the intensity of reduction. Precise evaluation of the reduction status of anaerobic natural envirsnmeilts should be determined by rigorous analysis of various chemical constituents, including manganese (IT) ,, iron (II), and sulfide. Comparism of results of the present study with those others indicated that microbial succession and appearance of reduced products closely parallel those found in flooded soils and sediments. The appearance of reduced products corresponded to the sequence roughly predicted by thermodynamics.