Variance of the Redox Potential Value in Two Anoxic Groundwater Systems

The use of redox potential measurements as an indicator of the redox milieu in geochemical environments is still subject of discussion. This chapter offers an empirical review of the redox potential measurements made in two groundwater systems over several years. The question is whether the measurements show statistically significant reproducibility so that the variance in values can be attributed to changes in the redox conditions. To maintain an empirical approach the correlation between EH-values and the chemical composition as well as the spatial distribution of the redox potential measurements was tested. To this end, first the overall variance of the data was evaluated. In the second step variogram analysis was employed to determine how much of the total variance could be explained with the spatial variability of groundwater chemistry. This is followed by a correlation analysis to check if the measured redox potential is also statistically determined by the groundwater composition.