Characterization of redox conditions in groundwater contaminant plumes

Evaluation of redox conditions in groundwater pollution plumes is often a p rerequisite for understanding the behaviour of the pollutants in the plume and for selecting remediation approaches. Measuring of redox conditions in pollution plumes is, however, a fairly recent issue and yet relative few ca ses have been reported. No standardised or generally accepted approach exis ts. Slow electrode kinetics and the common lack of internal equilibrium of redox processes in pollution plumes make, with a few exceptions, direct ele ctrochemical measurement and rigorous interpretation of redox potentials du bious, if not erroneous. Several other approaches have been used in address ing redox conditions in pollution plumes: redox-sensitive compounds in grou ndwater samples, hydrogen concentrations in groundwater, concentrations of volatile fatty acids in groundwater, sediment characteristics and microbial tools, such as MPN counts, PLFA biomarkers and redox bioassays. This paper reviews the principles behind the different approaches, summarizes methods used and evaluates the approaches based on the experience from the reporte d applications. (C) 2000 Elsevier Science B.V. All rights reserved.