A Model for Mass Transport Across the Sediment‐Water Interface

Voermans, Joey; Ghisalberti, Marco; Ivey, Gregory

doi:10.1002/2017wr022418

Cited by 45 publications

(100 citation statements)

References 53 publications

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“…This study adds to a growing literature that confirms turbulence directly controls mixing in highly permeable porous media (Ghisalberti, ; Katul et al, ; Voermans et al, ). Comparison of simulated and observed tracer injections in a coarse‐grained streambed shows that vertical mixing is highest at the SWI and decays exponentially with depth.…”

Section: Discussionsupporting

confidence: 64%

Effects of Turbulent Hyporheic Mixing on Reach‐Scale Transport

Roche

Bolster

et al. 2019

Water Resources Research

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Turbulence causes rapid mixing of solutes and fine particles between open channel flow and coarse‐grained streambeds. Turbulent mixing is known to control hyporheic exchange fluxes and the distribution of vertical mixing rates in the streambed, but it is unclear how turbulent mixing ultimately influences mass transport at the reach scale. We used a particle‐tracking model to simulate local‐ and reach‐scale solute transport for a stream with coarse‐grained sediments. Simulations were first used to determine profiles of vertical mixing rates that best described solute concentration profiles measured within a coarse granular bed in flume experiments. These vertical mixing profiles were then used to simulate a pulse solute injection to show the effects of turbulent hyporheic exchange on reach‐scale solute transport. Experimentally measured concentrations were best described by simulations with a nonmonotonic mixing profile, with highest mixing at the sediment–water interface and exponential decay into the bed. Reach‐scale simulations show that this enhanced interfacial mixing couples in‐stream and hyporheic solute transport. Coupling produces an interval of exponential decay in breakthrough curves and delays the onset of power law tailing. High streamwise velocities in the hyporheic zone reduce mass recovery in the water column and cause breakthrough curves to exhibit steeper power law slopes than predictions from mobile‐immobile modeling theory. These results demonstrate that transport models must consider the spatial variability of streamwise velocity and vertical mixing for both the stream and the hyporheic zone, and new analytical theory is needed to describe reach‐scale transport when high streamwise velocities are present in the hyporheic zone.

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Section: Discussionsupporting

confidence: 64%

Effects of Turbulent Hyporheic Mixing on Reach‐Scale Transport

Roche

Bolster

et al. 2019

Water Resources Research

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show abstract

“…This study adds to a growing literature that confirms turbulence directly controls mixing in highly-permeable porous media (Ghisalberti, 2009;Katul et al, 2013;Voermans et al, 2018). Comparison of simulated and observed tracer injections in a coarse-grained streambed shows that vertical mixing is highest at the SWI and decays exponentially with depth.…”

Section: Discussionsupporting

confidence: 57%

Effects of turbulent hyporheic mixing on reach-scale transport

Kevin¹,

Li²,

Bolster³

et al. 2019

Preprint

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Turbulence causes rapid mixing of solutes and fine particles between open channel flow and coarse-grained streambeds. Turbulent mixing is known to control hyporheic exchange fluxes and the distribution of vertical mixing rates in the streambed, but it is unclear how turbulent mixing ultimately influences mass transport at the reach scale. We used a particle-tracking model to simulate local- and reach-scale solute transport for a stream with coarse-grained sediments. Simulations were first used to determine profiles of vertical mixing rates that best described solute concentration profiles measured within a coarse granular bed in flume experiments. These vertical mixing profiles were then used to simulate a pulse solute injection to show the effects of turbulent hyporheic exchange on reach-scale solute transport. Experimentally measured concentrations were best described by simulations with a non-monotonic mixing profile, with highest mixing at the sediment-water interface and exponential decay into the bed. Reach-scale simulations show that this enhanced interfacial mixing couples in-stream and hyporheic solute transport. Coupling produces an interval of exponential decay in breakthrough curves and delays the onset of power-law tailing. High streamwise velocities in the hyporheic zone reduced mass recovery in the water column and caused breakthrough curves to exhibit steeper power-law slopes than predictions from mobile-immobile modeling theory. These results demonstrate that transport models must consider the spatial variability of streamwise velocity and vertical mixing for both the stream and the hyporheic zone, and new analytical theory is needed to describe reach-scale transport when high streamwise velocities are present in the hyporheic zone.

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“…Advective models are notable for their relatively faithful representation of the laminar flow fields generated by bedform pumping (Elliott & Brooks, 1997a, 1997b). An advantage of diffusive models is their ability to incorporate multiple mechanisms for mass transport across the SWI (i.e., not just bedform pumping) including molecular diffusion, turbulent diffusion, and turbulent dispersion (Chandler et al, 2016;Bottacin-Busolin, 2017;Grant, Azizian, et al, 2018;Grant, Gomez-Velez, & Ghisalberti, 2018;Grant et al, 2020;Roche et al, 2019;Voermans et al, 2017Voermans et al, , 2018.…”

Section: Introductionmentioning

confidence: 99%

Unifying Advective and Diffusive Descriptions of Bedform Pumping in the Benthic Biolayer of Streams

Grant

Monofy

Boano

et al. 2020

Water Resources Research

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Many water quality and ecosystem functions performed by streams occur in the benthic biolayer, the biologically active upper (~5 cm) layer of the streambed. Solute transport through the benthic biolayer is facilitated by bedform pumping, a physical process in which dynamic and static pressure variations over the surface of stationary bedforms (e.g., ripples and dunes) drive flow across the sediment-water interface. In this paper we derive two predictive modeling frameworks, one advective and the other diffusive, for solute transport through the benthic biolayer by bedform pumping. Both frameworks closely reproduce patterns and rates of bedform pumping previously measured in the laboratory, provided that the diffusion model's dispersion coefficient declines exponentially with depth. They are also functionally equivalent, such that parameter sets inferred from the 2D advective model can be applied to the 1D diffusive model, and vice versa. The functional equivalence and complementary strengths of these two models expand the range of questions that can be answered, for example, by adopting the 2D advective model to study the effects of geomorphic processes (such as bedform adjustments to land use change) on flow-dependent processes and the 1D diffusive model to study problems where multiple transport mechanisms combine (such as bedform pumping and turbulent diffusion). By unifying 2D advective and 1D diffusive descriptions of bedform pumping, our analytical results provide a straightforward and computationally efficient approach for predicting, and better understanding, solute transport in the benthic biolayer of streams and coastal sediments. Plain Language Summary How far and fast pollutants travel downstream is often conditioned on what happens in a thin veneer of biologically active bottom sediments called the benthic biolayer. However, before a pollutant can be removed in the benthic biolayer, it must first be transported across the sediment-water interface and through the interstitial fluids of these surficial sediments. In this paper we demonstrate that one important mechanism for transporting solutes to, and through, the benthic biolayerbedform pumping-can be interchangeably represented as either a two-dimensional advective process or a one-dimensional dispersion process. The complementary nature of these models expands the range of benthic biolayer processes that can be studied and predicted with the end goal of improving coastal and stream water quality.

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A Model for Mass Transport Across the Sediment‐Water Interface

Cited by 45 publications

References 53 publications

Effects of Turbulent Hyporheic Mixing on Reach‐Scale Transport

Effects of Turbulent Hyporheic Mixing on Reach‐Scale Transport

Effects of turbulent hyporheic mixing on reach-scale transport

Unifying Advective and Diffusive Descriptions of Bedform Pumping in the Benthic Biolayer of Streams

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