A review of the effects of iron redox cycles on smectite properties

The oxidation state of Fe in soils is one of the few properties that can be altered in situ and is known to have a large effect on chemical and physical properties. Understanding this phenomenon enables the possible manipulation or management of the soil in such a way as to maximize the benefit of such changes in properties. The effects of redox cycles, however, are less understood because most studies have focused only on a single reduction event. The purpose of this report is to review the current state of knowledge of the effects of redox cycles on clay and soil behavior, with the hope that this background will encourage further investigations of these processes. Evidence clearly indicates that the means by which reduction of Fe in clay minerals occurs significantly influences the potential reversibility of the process.