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

JOURNAL OF HYDROLOGY

卷:559

Article

Cook, Peter G.^1,2  Rodellas, Valenti³  Andrisoa, Aladin³  Stieglitz, Thomas C.^3,4 

[1] Flinders Univ S Australia, Coll Sci & Engn, NCGRT, Adelaide, SA 5001, Australia

[2] Aix Marseille Univ, IMeRA, F-13000 Marseille, France

[3] Aix Marseille Univ, CNRS, IRD, CEREGE,Coll France, F-13545 Aix En Provence, France

[4] James Cook Univ, Ctr Trop Water & Aquat Ecosyst Res, Townsville, Qld 4811, Australia

关键词: Porewater exchange;    Recirculated seawater;    Benthic flux;    Lake;    Tracers;    Radon;   

DOI  :  10.1016/j.jhydrol.2018.02.070

来源: Elsevier

【 摘 要 】

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. (C) 2018 Elsevier B.V. All rights reserved.

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