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

Abstract

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.

Physicochemistry of Iko River Channel in Nigeria and the Related Human Health Problems

“…This could be attributed to the dilution of the concentration of contaminants as the water flows downward 110,111 . This indicated that the contaminants in the studied water channel were diluted by the flow of the river 112,113 .…”

Accelerating regional-scale groundwater flow simulations with a hybrid deep neural network model incorporating mixed input types: A case study of the northeast Qatar aquifer

“…This discretization is often achieved through finite difference or finite element methods, and the process is iteratively repeated at each time step. These numerical models are extensively employed in aquifer resource management (Omar et al 2020;Miro et al 2021;Ostad-Ali-Askari & Shayannejad 2021), design of aquifer storage and recovery schemes (LaHaye et al 2021;Tiwari et al 2022Tiwari et al , 2023, drought risk management (Shivakoti et al 2019;Wossenyeleh et al 2021), and aquifer pollution control (Robinson et al 2009;Guo et al 2021;Panjehfouladgaran & Rajabi 2022;Shakeri et al 2023). However, the computational expense of numerical methods used in regional groundwater simulations can pose a significant obstacle for tasks that involve repeated simulations, such as uncertainty analysis and simulation-based optimization.…”

Assessment of Seawater Intrusion in Coastal Aquifers Using Multivariate Statistical Analyses and Hydrochemical Facies Evolution-Based Model

“…In addition, coastal aquifers are subject to the inflow of seawater, which represents the main limitation for groundwater uses [ 16 , 17 ]. Saltwater intrusion can be considered a very serious hazard to coastal areas that threatens fresh water supplies needed for livelihood [ 18 ].…”