Feasibility study of long-term continuous field measurement of soil redox potential

Abstract

An in situ and continuous redox potential measurement protocol for soils and groundwater was optimized, as part of a research that assays the redox potential changes in recharge basin soils during wastewater reclamation using the Soil Aquifer Treatment (SAT). The results show that it is possible to measure continuously and reliably the redox potential in the soil profile of the recharge basins and in the groundwater by using a combined Pt‖Ag|AgCl cell (electrode), a specialized interface, and a portable data-logger. Redox potential values measured before true local equilibration of the electrodes was reached are interpreted as “mixed-potentials” strongly biased by the presence of oxygen near the electrode. Uninterrupted and non-disturbing measurements were carried out in the field for relatively long periods (few days to few weeks) giving reliable information on the temporal cycling of the redox potential in the soil profile during wastewater recharge cycles. The method was found to be dependable, non-expensive and easy to apply.

Acknowledgments

This project was part of an extended study of heavy metal and trace element adsorption to recharge basin soils of Shafdan reclamation project and was partially supported by Mekorot Water Co., Israel and by a fellowship of the Hebrew University to G. Eshel. We would like to acknowledge the useful help and cooperation of the Shafdan operation crew, especially of N. Icekson-Tal, R. Blank, and G. Shoham. We are also grateful to D. Broker from Fourier Systems Co., Israel for technical support. The field and laboratory help provided by Y. Yablekovich, Y. Shachar and, in particular, D. Greenwald from the Dept. of Soils and Water Sciences, is gratefully acknowledged.