tracers and groundwater

tracers and groundwater Tracers of groundwater flow include both naturally occurring and artificially introduced dissolved materials, or solutes. Monitoring of tracers in wells or springs can provide information on directions and rates of flow as well as on the network of permeable features, such as fractures, that form the pathways of groundwater movement. Many tracer studies in limestone aquifers with significant solution-enhanced fractures or caves have employed fluorescent dyes that can be detected at low concentrations. Such studies have demonstrated connections between wells and springs located hundreds of metres apart, with estimated flow velocities exceeding many kilometres per day. At the other extreme of flow velocities, radioactive isotopes such as tritium (³H) and chlorine-36 (³⁶Cl), which were introduced to the hydrological cycle through nuclear weapons fallout, have been used to trace infiltration of water through the unsaturated zone at rates of millimetres per year. Experiments involving the injection of water tagged with dissolved chloride and bromide salts have been used to develop an improved understanding of dispersion in aquifers and to characterize sites proposed for radioactive waste disposal.

J. Bahr

Bibliography

Bonacci, O. (1987) Karst hydrology. Springer-Verlag, Berlin.