Accelerated measurement of groundwater redox potentials: method and application

Comparison tests between in-line mechanically polished and untreated Pt working electrodes were performed for redox potential measurements of two groundwaters. The redox potentials of these two waters of different types, which are governed, respectively, by sulphide or iron species, the latter being affected by the dissolved oxygen content, were measured on-line in a pressurised or non-pressurised flow through cell. Experimental data are compared with the potential calculated using Nernst derived equations. An accelerated record of the constant redox potential can be achieved within a few minutes with the in-line polished electrode, while measurements with an untreated electrode required hours or days. The use of pressurised cell may also optimise the redox measurement. Methodology, precision, accuracy and reproducibility are commented upon. (C) 1999 Elsevier Science B.V. All rights reserved.