Evaluation of 224Ra as a tracer for submarine groundwater discharge in Long Island Sound (NY)

García-Orellana, Jordi; Cochran, J. Kirk; Bokuniewicz, Henry; Daniel, J.W.R.; Rodellas, Valentí; Heilbrun, Christina

doi:10.1016/j.gca.2014.05.009

Cited by 49 publications

(28 citation statements)

References 48 publications

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“…These fluxes are mainly reflecting molecular diffusion and represent an upper estimate, since the continuous replacement of overlying waters with Rafree water maximizes the gradient between pore and overlying waters (Beck et al, 2007;Rodellas et al, 2012). Fluxes are comparable to those obtained in previous studies in muddy sediments from coastal Mediterranean environments (Garcia-Solsona et al, 2008b) and throughout the world (Beck et al, 2007;Garcia-Orellana et al, 2014;.…”

Section: Diffusive Sediment Fluxessupporting

confidence: 81%

“…However, sediments can represent a relevant source of Ra isotopes in those systems covered by fine-grained sediments and/or affected by processes that favor Ra exchange across the sediment-water interface, such as bioirrigation, sediment resuspension, seasonal hypoxia and short-scale (mm to cm) porewater exchange driven by pressure gradients (Breier et al, 2009(Breier et al, , 2010Colbert and Hammond, 2008;Garcia-Orellana et al, 2014;Gleeson et al, 2013), as we also showed in this work. In addition, Ra inputs from sediments can also be relevant and comparable to those gains from SGD in largescale studies, such as those conducted in entire basins where inputs from the entire continental shelf must be considered Rodellas et al, in press).…”

Section: Sediment Influence On Ra Mass Balancessupporting

confidence: 76%

“…In all these environments, the estimation of SGD relies on an appropriate characterization of Ra fluxes from sediment sources. However, Ra flux from sediments might be difficult to quantify, since it depends on several parameters highly variable in space (e.g., sediment grain size, porosity, redox state) and time (e.g., amount of sediments resuspended, frequency of resuspension events, bioturbation) (Breier et al, 2010;Garcia-Orellana et al, 2014;. For instance, showed that Ra fluxes from fine-grained sediments are commonly 1-2 orders of magnitude higher than those from coarse-grained sediments, requiring a detailed knowledge of the relative extension of each type of sediment.…”

Section: Sediment Influence On Ra Mass Balancesmentioning

confidence: 99%

“…Most studies involving Ra isotopes as tracers of SGD have shown that inputs of Ra from seafloor sediments are often small in relation to the SGD source term (Beck et al, 2007;Charette et al, 2003;Garcia-Solsona et al, 2008b;Rama and Moore, 1996;Rodellas et al, 2012). Conversely, recent studies in shallow embayments with fine-grained sediments and/or affected by processes that favor Ra exchange across the sediment-water interface (e.g., bioirrigation, resuspension, hypoxia) have demonstrated that the sedimentary source can supply a relevant flux of Ra isotopes, which may be comparable to SGD-derived Ra inputs (Breier et al, 2009(Breier et al, , 2010Colbert and Hammond, 2008;Garcia-Orellana et al, 2014;Gleeson et al, 2013). The relevance of the sedimentary source may be particularly important for short-lived Ra isotopes ( 223 Ra and 224 Ra), since their fast regeneration time within the surficial sediments allows its almost-continuous release to the water column.…”

Section: Introductionmentioning

confidence: 99%

“…Seafloor sediments may be a continuous source of Ra isotopes to the water column not only through diffusion, erosion or resuspension, but also through short-scale recirculation processes (mm to cm), such as topography-induced advection, wave pumping, ripple migration, shear and bioirrigation (Breier et al, 2009;Garcia-Orellana et al, 2014;Rama and Moore, 1996;Santos et al, 2012). Most studies involving Ra isotopes as tracers of SGD have shown that inputs of Ra from seafloor sediments are often small in relation to the SGD source term (Beck et al, 2007;Charette et al, 2003;Garcia-Solsona et al, 2008b;Rama and Moore, 1996;Rodellas et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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The influence of sediment sources on radium-derived estimates of Submarine Groundwater Discharge

et al. 2015

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Section: Diffusive Sediment Fluxessupporting

confidence: 81%

Section: Sediment Influence On Ra Mass Balancessupporting

confidence: 76%

Section: Sediment Influence On Ra Mass Balancesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The influence of sediment sources on radium-derived estimates of Submarine Groundwater Discharge

et al. 2015

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Quantifying Surface Water, Porewater, and Groundwater Interactions Using Tracers: Tracer Fluxes, Water Fluxes, and End‐member Concentrations

Cook

Rodellas

Stieglitz

2018

Water Resources Research

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Tracer approaches to estimate both porewater exchange (the cycling of water between surface water and sediments, with zero net water flux) and groundwater inflow (the net flow of terrestrially derived groundwater into surface water) are commonly based on solute mass balances. However, this requires appropriate characterization of tracer end‐member concentrations in exchanging or discharging water. Where either porewater exchange or groundwater inflow to surface water occur in isolation, then the water flux is easily estimated from the net tracer flux if the end‐member is appropriately chosen. However, in most natural systems porewater exchange and groundwater inflow will occur concurrently. Our analysis shows that if groundwater inflow (Qg) and porewater exchange (Qp) mix completely before discharging to surface water, then the combined water flux (Qg + Qp) can be approximated by dividing the combined tracer flux by the difference between the porewater and surface water concentrations, (cp – c). If Qg and Qp do not mix prior to discharge, then (Qg + Qp) can only be constrained by minimum and maximum values. The minimum value is obtained by dividing the net tracer flux by the groundwater concentration, and the maximum is obtained by dividing by (cp – c). Dividing by the groundwater concentration gives a maximum value for Qg. If porewater exchange and groundwater outflow occur concurrently, then dividing the net tracer flux by (cp – c) will provide a minimum value for Qp. Use of multiple tracers, and spatial and temporal replication should provide a more complete picture of exchange processes and the extent of subsurface mixing.

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Conceptual uncertainties in groundwater and porewater fluxes estimated by radon and radium mass balances

Rodellas

Stieglitz

Tamborski

et al. 2021

Limnology & Oceanography

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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.

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Evaluation of 224Ra as a tracer for submarine groundwater discharge in Long Island Sound (NY)

Cited by 49 publications

References 48 publications

The influence of sediment sources on radium-derived estimates of Submarine Groundwater Discharge

The influence of sediment sources on radium-derived estimates of Submarine Groundwater Discharge

Quantifying Surface Water, Porewater, and Groundwater Interactions Using Tracers: Tracer Fluxes, Water Fluxes, and End‐member Concentrations

Conceptual uncertainties in groundwater and porewater fluxes estimated by radon and radium mass balances

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