Radium Mass Balance Sensitivity Analysis for Submarine Groundwater Discharge Estimation in Semi-Enclosed Basins : The Case Study of Long Island Sound
Tamborski, Joseph (Stony Brook University)
Cochran, J. Kirk (Stony Brook University)
Bokuniewicz, Henry (Stony Brook University)
Heilbrun, Christina (Stony Brook University)
García Orellana, Jordi (Universitat Autònoma de Barcelona. Departament de Física)
Rodellas, Valentí (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Wilson, Robert (Stony Brook University)

Date:	2020
Abstract:	Estimation of submarine groundwater discharge (SGD) to semi-enclosed basins by Ra isotope mass balance is herein assessed. We evaluate 224Ra, 226Ra, and 228Ra distributions in surface and bottom waters of Long Island Sound (CT-NY, United States) collected during spring 2009 and summer 2010. Surface water and bottom water Ra activities display an apparent seasonality, with greater activities during the summer. Long-lived Ra isotope mass balances are highly sensitive to boundary fluxes (water flux and Ra activity). Variation (50%) in the 224Ra, 226Ra, and 228Ra offshore seawater activity results in a 63-74% change in the basin-wide 226Ra SGD flux and a 58-60% change in the 228Ra SGD flux, but only a 4-9% change in the 224Ra SGD flux. This highlights the need to accurately constrain long-lived Ra activities in the inflowing and outflowing water, as well as water fluxes across boundaries. Short-lived Ra isotope mass balances are sensitive to internal Ra fluxes, including desorption from resuspended particles and inputs from sediment diffusion and bioturbation. A 50% increase in the sediment diffusive flux of 224Ra, 226Ra, and 228Ra results in a ∼30% decrease in the 224Ra SGD flux, but only a ∼6-10% decrease in the 226Ra and 228Ra SGD flux. When boundary mixing is uncertain, 224Ra is the preferred tracer of SGD if sediment contributions are adequately constrained. When boundary mixing is well-constrained, 226Ra and 228Ra are the preferred tracers of SGD, as sediment contributions become less important. A three-dimensional numerical model is used to constrain boundary mixing in Long Island Sound (LIS), with mean SGD fluxes of 1. 2 ± 0. 9 × 1013 L y-1 during spring 2009 and 3. 3 ± 0. 7 × 1013 L y-1 during summer 2010. The SGD flux to LIS during summer 2010 was one order of magnitude greater than the freshwater inflow from the Connecticut River. The maximum marine SGD-driven N flux is 14 ± 11 × 108 mol N y-1 and rivals the N load of the Connecticut River.
Grants:	Ministerio de Economía y Competitividad MDM-2015-0552 Agència de Gestió d'Ajuts Universitaris i de Recerca 2017/SGR-1588 Agència de Gestió d'Ajuts Universitaris i de Recerca 2017/BP-00334
Note:	Unidad de excelencia María de Maeztu CEX2019-000940-M
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Long Island Sound ; Nitrogen ; Porewater exchange ; Radium isotopes ; Submarine groundwater discharge
Published in:	Frontiers in Environmental Science, Vol. 8 (July 2020) , art. 108, ISSN 2296-665X

DOI: 10.3389/fenvs.2020.00108

13 p, 1.8 MB

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Research literature > UAB research groups literature > Research Centres and Groups (research output) > Experimental sciences > Institut de Ciència i Tecnologia Ambientals (ICTA)
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