An Overview of 14C Analysis in the Study of Groundwater

This paper provides a summary overview of the current state-of-art in the radiocarbon dating of groundwater. While the use of natural 14C measurements in applied hydrogeology still presents a difficult challenge, meaningful dates can be achieved if they are determined and interpreted in conjunction with the analyses of other isotopic species that occur in the natural environment. Although 14C dating of groundwater can be, and often is, carried out as a matter of routine, any specific case study requires its own scientific design and effort. As is widely recognized, and discussed in considerable detail throughout the scientific literature, there are many hydrogeochemical reactions and/or physical processes that can alter the natural 14C enrichment measured in environmental materials. Fortunately, for fresh groundwater resources such effects are in general well defined and therefore of limited significance. The primary challenge in applied groundwater dating is with the development of the appropriate theoretical background against which 14C dates can be used to calibrate numerical analogues of the groundwater system. The hydraulic properties of each of the widely used finite-element models can be well estimated from numerous piezometric data and extrapolations. In contrast, only a few groundwater ages can be provided for the calibration of those models that are complex functions of aging mixture and sometimes also hydrochemical reactions.