CONSTRUCTION AND EVALUATION OF A REFERENCE ELECTRODE ASSEMBLY FOR USE IN MONITORING INSITU SOIL REDOX POTENTIALS

A simple procedure for the construction of inexpensive Ag,AgCl reference electrode assemblies is described. Disposable plastic syringes (60-cm3) were used to form the bodies of the electrode assemblies and small Ag,AgCl internal reference elements were made from silver wire. The internal reference elements were immersed in a solution of AgCl-saturated KCl, which also served as the salt bridge. Contact between the salt bridge and test solution or soil was made through a ceramic microtensiometer cup. This procedure yields reference electrode assemblies that perform as well as commercially available reference electrodes in terms of their stability and reproducibility. Because of their rugged construction and ease of maintenance, these reference electrode assemblies are ideal for use in the field. Moreover, they proved to be particularly useful when in situ soil redox potentials were monitored for 84 h.