Continuous Multiple Measurement of Soil Redox Potential Using Platinum Microelectrodes

Abstract

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.