Publication Date:
2022-05-26
Description:
© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Rodellas, V., Stieglitz, T. C., Tamborski, J. J., van Beek, P., Andrisoa, A., & Cook, P. G. Conceptual uncertainties in groundwater and porewater fluxes estimated by radon and radium mass balances. Limnology and Oceanography, (2021), https://doi.org/10.1002/lno.11678.
Description:
Radium isotopes and radon are routinely used as tracers to quantify groundwater and porewater fluxes into coastal and freshwater systems. However, uncertainties associated with the determination of the tracer flux are often poorly addressed and often neglect all the potential errors associated with the conceptualization of the system (i.e., conceptual uncertainties). In this study, we assess the magnitude of some of the key uncertainties related to the determination of the radium and radon inputs supplied by groundwater and porewater fluxes into a waterbody (La Palme Lagoon, France). This uncertainty assessment is addressed through a single model ensemble approach, where a tracer mass balance is run multiple times with variable sets of assumptions and approaches for the key parameters determined through a sensitivity test. In particular, conceptual uncertainties linked to tracer concentration, diffusive fluxes, radon evasion to the atmosphere, and change of tracer inventory over time were considered. The magnitude of porewater fluxes is further constrained using a comparison of independent methods: (1) 224Ra and (2) 222Rn mass balances in overlying waters, (3) a model of 222Rn deficit in sediments, and (4) a fluid‐salt numerical transport model. We demonstrate that conceptual uncertainties are commonly a major source of uncertainty on the estimation of groundwater or porewater fluxes and they need to be taken into account when using tracer mass balances. In the absence of a general framework for assessing these uncertainties, this study provides a practical approach to evaluate key uncertainties associated to radon and radium mass balances.
Description:
This research is a contribution to the ANR @RAction chair (ANR‐14‐ACHN‐0007‐01—T Stieglitz) and Labex OT‐Med (ANR‐11‐LABEX‐0061, part of the “Investissements d'Avenir” program through the A*MIDEX project ANR‐11‐IDEX‐0001‐02) funded by the French National Research Agency (ANR). This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska‐Curie grant 748896. V. Rodellas acknowledges financial support from the Beatriu de Pinós postdoctoral programme of the Catalan Government (2017‐BP‐00334). P. van Beek acknowledges financial support from the ANR (MED‐SGD project, ANR‐15‐CE01‐0004). We thank S. Thomas (Labex OT‐Med) for constructive comments and M. Diego‐Feliu for his help on statistical analysis. This study contributes to the work carried out by the MERS research group 2017‐SGR‐1588.
Repository Name:
Woods Hole Open Access Server
Type:
Article
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