Solute transport influenced by unstable flow in beach aquifers

Shen, Chengji; Zhang, Chenming; Kong, Jun; Xin, Pei; Lu, Chunhui; Zhao, Zhimiao; Li, Ling

doi:10.1016/j.advwatres.2019.01.009

Cited by 48 publications

(55 citation statements)

References 61 publications

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“…Further, the spatial variation of the mass center (i.e., centroids) is used to depict the solute mixing degree. The spatial moments of centroids were calculated using the method of spatial moment estimation, which is well described in previous literature (e.g., Freyberg, 1986;Shen et al, 2019). A brief description of calculation equations is provided in the SI.…”

Section: Spatial Moment Estimationmentioning

confidence: 99%

Effects of Tidally Varying Salinity on Groundwater Flow and Solute Transport: Insights From Modelling an Idealized Creek Marsh Aquifer

Xiao

Xia

et al. 2019

Water Resources Research

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Most existing numerical research on tide‐induced groundwater dynamics assumes a constant surface water salinity on the seaward boundary (constant salinity case). Few studies have investigated the influence of tidally varying salinity on shallow groundwater dynamics in coastal aquifers (tidal salinity case). We compiled field observations of tidally varying salinity in multiple estuaries across the eastern coast of China and a tidal creek in North Inlet‐Winyah Bay, United States. Numerical simulations were then conducted to explore the effect of tidally varying salinity on groundwater flow and salt transport in an idealized creek marsh aquifer. Results showed that the upper saline plume and classical saltwater wedge appeared in all cases, but the salinity in the saltwater wedge was diluted in the tidal salinity cases. Notably, groundwater transit times were shorter in the tidal salinity case than in the constant salinity case, especially under the creek bottom. Quantitative analyses indicated that tidally varying salinity significantly enhanced surface water‐groundwater exchange, increasing submarine groundwater discharge by 10% and the total inflow of surface water across the water‐sediment interface by 7%. As the density of groundwater differs from that of the overlying surface water, fingered saltwater flow formed in sediments under the creek bottom, leading to some small local water circulation cells. These small cells reduced groundwater transit times and almost doubled the water exchange rate. Coupling the density‐dependent flow to a simplified nitrogen reaction network revealed that the tidally varying salinity may have the potential to influence nitrogen biogeochemical transformations that modify nitrogen loads prior to discharge.

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Section: Spatial Moment Estimationmentioning

confidence: 99%

Effects of Tidally Varying Salinity on Groundwater Flow and Solute Transport: Insights From Modelling an Idealized Creek Marsh Aquifer

Xiao

Xia

et al. 2019

Water Resources Research

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“…In recent years, the laboratory experiment, analytical solution and numerical simulation were used to solve the problem of contamination migration in coastal zones [ 8 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ]. The experimental method has been applied earlier to resolve the problem of pollutant migration in coastal aquifer.…”

Section: Introductionmentioning

confidence: 99%

“…For example, Guo et al [ 41 ] developed the numerical model to simulate the contaminant transport at a gravel beach, combining with the field experiment. Shen et al [ 46 ] considered contaminant transport affected by unstable flow in the beach aquifers by numerical simulation.…”

Section: Introductionmentioning

confidence: 99%

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Contamination Transport in the Coastal Unconfined Aquifer under the Influences of Seawater Intrusion and Inland Freshwater Recharge—Laboratory Experiments and Numerical Simulations

Guo

Zhao

et al. 2021

IJERPH

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The coupled effect of seawater intrusion and inland freshwater recharge plays an important role in contamination transport in coastal heterogeneous aquifer. In this study, the effects of seawater intrusion and inland recharge on contamination transport were investigated by conducting laboratory experiments and numerical simulations. The laboratory tests were conducted in a sand tank considering two scenarios, namely the conditions of landward and seaward hydraulic gradients. The SEAWAT software was applied for validating the contaminant transport in coastal heterogeneous aquifer. The results indicated that the simulated seawater wedge and contours of the saltwater contaminant matched the observed ones well. The length of the seawater wedge in the scenario of seaward hydraulic gradient was smaller than that in the scenario of landward hydraulic gradient, which reflected that the large quantity of inland recharge have a negative effect on the invasion process of seawater. The plume moved mainly downward in the heterogeneous unconfined aquifer for both scenarios. The pollution plume became concave at the interface between each two layers, which was because the velocity of contaminant plume migration increased gradually from the upper layer to lower layer. The migration direction of the front of the plume was consistent with the direction of hydraulic gradient, which indicated that it was influenced by the water flowing. The maximum area of plume in the scenario of seaward hydraulic gradient was slightly smaller than that in the scenario of landward hydraulic gradient. The maximum area and vertical depth of the pollutant plume were sensitive to the hydraulic conductivity, dispersivity and contamination concentration. This study was of great significance to the controlling of pollution and utilization of freshwater resources in coastal areas.

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“…While tidal effects on SGD and salinity distributions in subterranean estuaries have been studied extensively, previous studies predominately considered single-frequency (monochromatic) tides (Robinson et al, 2007b;Kuan et al, 2019;Shen et al, 2019;Yu et al, 2019a), bichromatic springneap tides (Robinson et al, 2007a;Abarca et al, 2013;Heiss and Michael, 2014;Buquet et al, 2016), or fitted tidal variations with several primary constituents (Levanon et al, 2016;Geng and Boufadel, 2017;Levanon et al, 2017;Yu et al, 2019b). Coastal aquifer systems are commonly subjected to oceanic tidal fluctuations, which likely contain tens of constituents with different fluctuation frequencies and amplitudes (Pawlowicz et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Effects of Multiconstituent Tides on a Subterranean Estuary With Fixed-Head Inland Boundary

Xin

Shen

et al. 2021

Front. Environ. Sci.

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While tides of multiple constituents are common in coastal areas, their effects on submarine groundwater discharge (SGD) and salinity distributions in unconfined coastal aquifers are rarely examined, with the exception of a recent study that explored such effects on unconfined aquifers with fixed inland freshwater input. For a large proportion of the global coastline, the inland areas of coastal aquifers are topography-limited and controlled by constant heads. Based on numerical simulations, this article examines the variation of SGD and salinity distributions in coastal unconfined aquifers with fixed-head inland boundaries at different distances from the shoreline (i.e., 50, 100, 150, and 200 m). The results showed that the fluctuation intensity of freshwater input was enhanced as the inland aquifer extent decreased, e.g., the range of tide-induced fluctuations in freshwater input increased by around 5 times as the inland aquifer extent decreased from 200 to 50 m. The frequency spectra of the fluctuations of SGD and salinity distributions showed that the coastal aquifer of a shorter inland aquifer extent smoothed out fewer high-frequency tidal constituents but enhanced interaction among different tidal constituents. The interaction among tidal constituents generated new low-frequency signals in the freshwater input and salinity distributions. Regressions based on functional data analysis demonstrated that the inland freshwater input and salinity distributions at any given moment were related to the antecedent (previous) tidal conditions weighted using the probability density function of the Gamma distribution. The influence of the antecedent tidal conditions depended on the inland aquifer extent.

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Solute transport influenced by unstable flow in beach aquifers

Cited by 48 publications

References 61 publications

Effects of Tidally Varying Salinity on Groundwater Flow and Solute Transport: Insights From Modelling an Idealized Creek Marsh Aquifer

Effects of Tidally Varying Salinity on Groundwater Flow and Solute Transport: Insights From Modelling an Idealized Creek Marsh Aquifer

Contamination Transport in the Coastal Unconfined Aquifer under the Influences of Seawater Intrusion and Inland Freshwater Recharge—Laboratory Experiments and Numerical Simulations

Effects of Multiconstituent Tides on a Subterranean Estuary With Fixed-Head Inland Boundary

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