Subsurface Mixing Dynamics Across the Salt-Freshwater Interface

Mixing along the salt-freshwater interface is critical for geochemical reactions, transport, and transformation of nutrients and contaminants in coastal ecosystems. However, the mechanisms and controls of mixing are not well understood. We develop an analytical model, based on the coupling between f...

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Bibliographic Details
Authors: De Vriendt, Kevin, Le Borgne, T., Pool, María, Dentz, Marco
Format: article
Status:Published version
Publication Date:2022
Country:España
Institution:Consejo Superior de Investigaciones Científicas (CSIC)
Repository:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/270426
Online Access:http://hdl.handle.net/10261/270426
https://api.elsevier.com/content/abstract/scopus_id/85128717231
Access Level:Open access
Keyword:Mixing
Analytical models
Coastal groundwater
Flow deformation
Numerical modeling
Seawater intrusion
Description
Summary:Mixing along the salt-freshwater interface is critical for geochemical reactions, transport, and transformation of nutrients and contaminants in coastal ecosystems. However, the mechanisms and controls of mixing are not well understood. We develop an analytical model, based on the coupling between flow deformation and dispersion, which predicts the mixing dynamics along the interface for steady-state flow in coastal aquifers. The analytical predictions are compared with the results of detailed numerical simulations, which show that nonuniform flow fields, inherent to seawater intrusion in coastal aquifer, result in a non-monotonic evolution of mixing width and mixing rates along the interface. The analytical model accurately captures these dynamics over a range of freshwater flow rates and dispersivities. It predicts the evolution of the mixing width and mixing rates along the interface, offering a new framework for understanding and modeling mixing and reaction processes in coastal aquifers.