Exchange across the sediment-water interface quantified from porewater radon profiles

Cook, Peter G., Rodellas, Valentí, Adnrisoa, Aladin, and Stieglitz, Thomas C. (2018) Exchange across the sediment-water interface quantified from porewater radon profiles. Journal of Hydrology, 559. pp. 873-883.

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Abstract

Water recirculation through permeable sediments induced by wave action, tidal pumping and currents enhances the exchange of solutes and fine particles between sediments and overlying waters, and can be an important hydro-biogeochemical process. In shallow water, most of the recirculation is likely to be driven by the interaction of wave-driven oscillatory flows with bottom topography which can induce pressure fluctuations at the sediment-water interface on very short timescales. Tracer-based methods provide the most reliable means for characterizing this short-timescale exchange. However, the commonly applied approaches only provide a direct measure of the tracer flux. Estimating water fluxes requires characterizing the tracer concentration in discharging porewater; this implies collecting pore water samples at shallow depths (usually a few mm, depending on the hydrodynamic dispersivity), which is very difficult with commonly used techniques. In this study, we simulate observed vertical profiles of radon concentration beneath shallow coastal lagoons using a simple water recirculation model that allows us to estimate water exchange fluxes as a function of depth below the sediment-water interface. Estimated water fluxes at the sediment water interface at our site were 0.18-0.25 m/day, with fluxes decreasing exponentially with depth. Uncertainty in dispersivity is the greatest source of error in exchange flux, and results in an uncertainty of approximately a factor-of-five.

Item ID: 53706
Item Type: Article (Research - C1)
ISSN: 0022-1694
Keywords: porewater exchange, recirculated seawater, benthic flux, lake, tracers, radon
Funders: French National Research Agency (ANR), Aix-Marseille Université, European Union's Horizon 2020 Research and Innovation Program (EU)
Projects and Grants: ANR A*MIDEX project ANR-11-IDEX-0001-02, ANR @RAction chair medLOC ANR-14-ACHN-0007-01, ANR Labex OT-Med ANR-11-LABEX-0061, EU Marie Sklodowska-Curie grant agreement no. 748896
Date Deposited: 23 May 2018 07:32
FoR Codes: 04 EARTH SCIENCES > 0406 Physical Geography and Environmental Geoscience > 040608 Surfacewater Hydrology @ 25%
04 EARTH SCIENCES > 0403 Geology > 040305 Marine Geoscience @ 25%
04 EARTH SCIENCES > 0406 Physical Geography and Environmental Geoscience > 040603 Hydrogeology @ 50%
SEO Codes: 96 ENVIRONMENT > 9609 Land and Water Management > 960903 Coastal and Estuarine Water Management @ 50%
96 ENVIRONMENT > 9611 Physical and Chemical Conditions of Water > 961102 Physical and Chemical Conditions of Water in Coastal and Estuarine Environments @ 50%
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