The redox potential, i. e. a measure (in volts) of the affinity of a substance for electrons compared with hydrogen, may also be determined in the field using electrical, hand-held equipment, this time employing an inert oxidation-reduction electrode.
Electrical conductivity is typically measured in-situ, being an important, yet simple, indicator of pollution since the ability of water to conduct electricity increases as the proportion of dissolved ions increases. It can be measured directly through the insertion of probes and the resistance (or conductivity recorded) or indirectly through air-coupled “aerials”. However, because there are so many factors that affect electrical conductivity (e. g. presence of metals, saturation), it is normally best to use conductivity techniques as means of locating areas of anomalous response. These can then be investigated by alternative techniques to discover whether pollution is the cause and, if so, its degree and type.
