Electron intensity, the role of humic acids in extracellular electron transport and chemical determination of pE in natural waters

Abstract

Experimental systems demonstrate that humic acids are capable of accepting electrons from a wide spectrum of donors and transferring those electrons to a wide spectrum of acceptors, linking normally thermodynamically discrete redox couples. By functioning as a wide redox potential ‘flavoprotein’, humics encompass all the redox potentials pertinent to aquatic systems and hence determine relative electron activity, the negative log of which is pE. A chemically determined, system oxidation-reduction potential allows pE to be used along with pH in developing a biochemical framework for thermodynamically derived predictions of aquatic system behavior.