HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Rabenhorst, M. C. Articles by James, B. R. Search for Related Content PubMed Articles by Rabenhorst, M. C. Articles by James, B. R. GeoRef GeoRef Citation Agricola Articles by Rabenhorst, M. C. Articles by James, B. R. Related Collections Wetland Soils

WETLAND SOILS

Measurements of Soil Redox Potential

^a Dep. of Environ. Science and Technology, Univ. of Maryland, College Park, MD 20742
^b USDA-ARS, Hydrology and Remote Sensing Lab., Beltsville, MD 20705

^* Corresponding author (mrabenho{at}umd.edu).

Soil redox potentials (Eh) are commonly measured and operationally defined using platinum (Pt) electrodes, but there are variations in the methodology and instrumentation for measuring the associated voltages that may lead to imprecise and inaccurate estimates of oxidation–reduction intensity in the soil environment. Most field measurements of Eh are either made manually using a volt meter or automatically with a recording device such as a data logger. A mesocosm experiment was conducted to evaluate the impact of these two measurement approaches on resulting Eh values in three different wetland soils. Noticeable differences were observed between data collected using a multimeter (simple volt meter) and those collected with a data logger. Because the multimeter permitted the observed voltages to drift while the Pt and reference electrodes equilibrated following closure of the circuit, it was initially suspected that these were the more accurate data. By adding a 10-Mohm resistor (standard component of commercially available multimeters) to a closed circuit containing the Pt and reference electrodes, data loggers could be modified to collect data similar to those obtained using a multimeter. Further testing, however, demonstrated that the voltage drift observed when using a closed 10-Mohm circuit was an artifact of alterations in the electrochemical soil environment surrounding the Pt electrode. By using an instrument with very high (200 Gohm) input resistance, the artifactual drift could be essentially eliminated. Our comparisons and experiments suggest that the most accurate measurements of soil Eh and soil redox status are obtained using volt meters with high input resistance (e.g., 200 Gohm). Accurate Eh values also are obtained using data loggers (20 Gohm resistance) in the standard configuration that maintains an open circuit except during the actual instantaneous voltage measurement.

Abbreviations: IRIS, Indicator of Reduction in Soil • PVC, polyvinylchloride • SHE, standard hydrogen electrode

This article has been cited by other articles:

				M. C. Rabenhorst Making Soil Oxidation-Reduction Potential Measurements using Multimeters Soil Sci. Soc. Am. J., October 21, 2009; 73(6): 2198 - 2201. [Abstract] [Full Text] [PDF]