Groundwaters may be dated by using carbon 14, provided that the raw data are properly adjusted. However, adjustment factors determined from geochemical or isotopic measurements and based on simple models of carbonate dissolution do not always agree with adjustment factors obtained by independent means. In this paper, established adjustment methods are reinterpreted in terms of closed and open system models of carbonate dissolution, and it is suggested that these models provide a sounder framework for determining adjustment factors. Hypothetical and real examples are considered, and it is shown that some otherwise anomalous results may be explained in terms of the closed and open system models.
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