ABSTRACT
This chapter discusses the major emphasis is placed on changes in Eh and pH in relation to biogeochemical reactions of interest in wetlands and soils that undergo wetting and drying conditions. Oxidation and reduction reactions regulate many of the biogeochemical reactions in wetlands. Electrons are essential to many biogeochemical reactions. Oxidation, the loss of electrons, couples with reduction, the gain of electrons. The Eh of soil is determined by the concentration of oxidants and reductants. Aerobic organisms that oxidize organic substrates using oxygen as an electron acceptor must only develop a low reduction intensity so that oxygen accepts and is reduced to water. However, obligate anaerobic organisms such as sulfate reducers must exert a very high electron pressure or reduction intensity to cause the sulfate ion to accept electrons and become reduced to sulfide. The redox potential of soils is also influenced by frequent additions of organic substrates or soils high in native organic matter.
