Bayesian evaluation of groundwater age distribution using radioactive tracers and anthropogenic chemicals

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Publication Type pre-print
School or College College of Mines & Earth Sciences
Department <blank>
Creator Solomon, Douglas Kip
Other Author Massoudieh, Arash; Sharifi, Soroosh
Title Bayesian evaluation of groundwater age distribution using radioactive tracers and anthropogenic chemicals
Date 2012-01-01
Description The development of a Bayesian modeling approach for estimation of the age distribution of groundwater using radioactive isotopes and anthropogenic chemicals is described. The model considers the uncertainties associated with the measured tracer concentrations as well as the parameters affecting the concentration of tracers in the groundwater, and it provides the posterior probability densities of the parameters defining the groundwater age distribution using a Markov chain Monte Carlo method. The model also incorporates the effect of dissolution of aquifer minerals on diluting the 14C signature and the uncertainties associated with this process on the inferred age distribution parameters. Two demonstration modeling cases have been performed. First, the method was applied to simulated tracer concentrations at a discharge point of a hypothetical 2-D vertical aquifer with two recharge zones, leading to a mixed groundwater age distribution under different presumed uncertainties. When the error variance of the observed tracer concentrations is considered unknown, the method can estimate the parameters of the fitted exponential-lognormal distribution with a relatively narrow credible interval when five hypothetical samples are assumed to be collected at the discharge point. However, when a single sample is assumed, the credible intervals become wider, and credible estimations of the parameters are not obtained. Second, the method was applied to the data collected at La Selva Biological Station in Costa Rica. In this demonstration application, nine different forms of presumed groundwater age distributions have been considered, including four single forms and five mixed forms, assuming the groundwater consists of distinct young and old fractions. For the medium geometrical standard deviation dc,i = 1.41, the model estimates a young groundwater age of between 0 and 350 years, with the largest odds being given to a mean age of approximately 100 years, and a fraction of young groundwater of between 15% to roughly 60%, with the largest odds for 30%. However, the method cannot definitively rule out larger fractions of young groundwater. The model provides a much more uncertain estimation of the age of old groundwater, with a credible interval of between 20,000 to 200,000 years.
Type Text
Publisher American Geophysical Union (AGU)
Volume 48
Issue 9
First Page W09529
Dissertation Institution University of Utah
Language eng
Bibliographic Citation Massoudieh, A., Sharifi, S., & Solomon, D. K. (2010). Bayesian evaluation of groundwater age distribution using radioactive tracers and anthropogenic chemicals. Water Resources Research, 48(9), W09529.
Rights Management (c) Massoudieh, A., Sharifi, S., & Solomon, D. K. Bayesian evaluation of groundwater age distribution using radioactive tracers and anthropogenic chemicals. Water Resources Research, 48(9), W09529.prior to 2002), date. Copyright 2012 American Geophysical Union. Reproduced/modified by permission of American Geophysical Union.
Format Medium application/pdf
Format Extent 2,141,916 bytes
Identifier uspace,17961
ARK ark:/87278/s6zw24pj
Setname ir_uspace
Date Created 2012-10-29
Date Modified 2012-11-05
ID 708190
Reference URL https://collections.lib.utah.edu/ark:/87278/s6zw24pj
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