Continuous multiple measurement of soil redox potential using platinum microelectrodes

Redox potential (E-H) measurement is a reading of voltage difference between a working electrode such as a Pt electrode and a reference electrode inserted into the soil or various substrates. This study was conducted to develop a method for continuous, autonomous, and multiple E-H measurements using Pt microelectrodes connected to a data logger. A preliminary field experiment was carried out to assess the long-term viability of Pt microelectrodes installed in situ. A second experiment was conducted in the laboratory to test an interface designed to allow the stabilization of E-H measurements. The Pt microelectrodes and reference electrode showed reliable readings during the field trial and generally tested viable at the end of the four month experiment. However, discrepancies between logged E-H measurements and manually stabilized readings, particularly under moderate reductive conditions, emphasized the necessity to adapt the principle of manually stabilized readings to the use of a data logger. Laboratory data obtained from pairs of Pt microelectrodes and reference electrodes connected to a new homemade interface confirmed that instantaneous logged measurements led to the underestimation of E-H values by 140 mV in the critical and unstable range of 0 to 200 mV. Continuous, multiple measurements of stabilized E-H using Pt microelectrodes is now feasible using a stabilization interface placed between the microelectrode and the data logger.