A general reactive transport modeling framework for simulating and interpreting groundwater 14C age and δ 13C

S Salmon, Henning Prommer, J Park, Karina Meredith, J Turner, James McCallum

    Research output: Contribution to journalArticlepeer-review

    9 Citations (Scopus)

    Abstract

    A reactive transport modeling framework is presented that allows simultaneous assessment of groundwater flow, water quality evolution including δ13C, and 14C activity or "age". Through application of this framework, simulated 14C activities can be directly compared with measured 14C activities. This bypasses the need for interpretation of a 14C age prior to flow simulation through factoring out processes other than radioactive decay, which typically involves simplifying assumptions regarding spatial and temporal variability in reactions, flow, and mixing. The utility of the approach is demonstrated for an aquifer system with spatially variable carbonate mineral distribution, multiple organic carbon sources, and transient boundary conditions for 14C activity in the recharge water. In this case, the simulated 14C age was shown to be relatively insensitive to isotopic fractionation during DOC oxidation and variations in assumed DOC degradation behavior. We demonstrate that the model allows quantitative testing of hypotheses regarding controls on groundwater age and water quality evolution for all three carbon isotopes. The approach also facilitates incorporation of multiple environmental tracers and combination with parameter optimization techniques.

    Original languageEnglish
    Pages (from-to)359-376
    Number of pages18
    JournalWater Resources Research
    Volume51
    Issue number1
    DOIs
    Publication statusPublished - Jan 2015

    Keywords

    • C
    • environmental tracers
    • groundwater age
    • organic and inorganic carbon
    • reactive transport model
    • δ C

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