Principles and uncertainties of 14C age estimations for groundwater transport and resource evaluation

Radiocarbon (C-14) is useful for estimating groundwater ages for transport and water resource exploitation assessment. If the C-14 content of dissolved inorganic carbon (C-14(DIC)) is known, the age of groundwater can be estimated by applying a radiocarbon decay equation combined with an appropriate geochemical correction model. However, age determinations are subject to uncertainties caused by parameters which need to be estimated or assumed. Here, we discuss the principles of C-14-based groundwater age estimations and the corrections and errors that affect age determinations differently. Generally, the two factors that impact the results of C-14 groundwater age are Type-1 and Type-2 errors. Type-1 errors are pulse-type changes on derived groundwater ages that are independent of the water age. Type-2 errors cause gradual changes on derived groundwater C-14 ages that depend on the water age. The cumulative impact of these errors substantively reduces the accuracy and confidence of C-14 age determinations and corrections. When using C-14 for groundwater age, consideration of both error types along with the use of samples having a range of C-14(DIC) contents helps practitioners recognize and minimize C-14 age uncertainty, especially for groundwater ages of 30,000 years B.P.

Automated summary

The article discusses the principles and factors affecting C-14-based groundwater age estimations, identifying Type-1 and Type-2 errors as significant influences on the results. It also suggests methods to minimize uncertainty in C-14 age determinations, particularly for groundwater ages over 30,000 years BP.