Reaction-transport models for radiocarbon in groundwater: The effects of longitudinal dispersion and the use of Sr isotope ratios to correct for water-rock interaction

T. M. Johnson, D. J. DePaolo

Research output: Contribution to journalReview articlepeer-review

Abstract

We expand a model for isotope ratios in groundwater-rock systems to consider the ratio of 14C to dissolved inorganic carbon, or 'percent modern carbon' The model couples one-dimensional advection and dispersion with water-rock interaction and radioactive decay. We use a Fickian formulation to model longitudinal macrodispersion and present a formula for the groundwater velocity error introduced when dispersion is ignored, as a function of dispersivity and decrease in percent modern carbon. For example, if the longitudinal dispersivity were one tenth the length of observation and percent modern carbon decreased tenfold along a flow path, the error would be 23%. We also present a method for inversion of 87Sr/86Sr and 14C data to obtain carbonate dissolution rates and dissolution-corrected water velocities and apply this technique using published data from the Lincolnshire aquifer, England. The results are similar to those obtained using the δ13C method.

Original languageEnglish (US)
Pages (from-to)2203-2212
Number of pages10
JournalWater Resources Research
Volume32
Issue number7
DOIs
StatePublished - Jul 1 1996
Externally publishedYes

ASJC Scopus subject areas

  • Water Science and Technology

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