Soil Redox Potential and pH Controllers

Rapid changes in redox potential (Eh) and pH occur in wetland environments. Due to frequent hydrologic fluctuations, wetland soils and sediments can have Eh values ranging from 700 mV (under drainage conditions) to −300 mV (under prolonged flooding conditions). Redox potential is probably the best available simple indicator of the oxidation– reduction status of a system, and it covers the entire range across which various inorganic redox systems function. Therefore, determining soil redox potential and pH can significantly improve our understanding in wetland biogeochemistry. One experimental approach is to determine and to closely control the redox potential and pH at which various redox couples function. A redox potential–pH controller can be designed and constructed differently to fit individual research purposes and budgets. In this chapter, we will introduce basic components of the controller, provide some modification options, and present a fully automated system for biogeochemistry research. Abbreviations: ORP, oxidation–reduction potential.