Characterization of seawater intrusion and submarine groundwater discharge in alluvial coastal aquifers: field and laboratory approach

Aplicat embargament des de la data de defensa fins al 31 de desembre de 2020 Seawater intrusion (SWI) causes not only salinization of coastal aquifers, but also a reduction submarine groundwater discharge (SGD) and nutrient fluxes to marine ecosystems. We have developed a small scale experimental fi...

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Autor: Martínez, Laura
Formato: tesis doctoral
Fecha de publicación:2020
País:España
Recursos:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/230923
Acesso em linha:http://hdl.handle.net/10261/230923
Access Level:acceso abierto
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spelling Characterization of seawater intrusion and submarine groundwater discharge in alluvial coastal aquifers: field and laboratory approachMartínez, LauraAplicat embargament des de la data de defensa fins al 31 de desembre de 2020 Seawater intrusion (SWI) causes not only salinization of coastal aquifers, but also a reduction submarine groundwater discharge (SGD) and nutrient fluxes to marine ecosystems. We have developed a small scale experimental field site to gain insights into both SWI and SGD. The site is located in a coastal alluvial aquifer at the mouth of an ephemeral stream in the Maresme coastline (Barcelona, Spain). Here, we describe our attempts for a detailed site characterization, which was based on the four pillars of hydrogeology: geology (Lithological description and geochemical analysis of core), geophysics (borehole logs, Electrical Resistivity Tomography and thermal monitoring), hydraulics (pumping and tidal response tests) and hydrochemistry (major and minor elements, stable isotopes and Radium isotopes for SGD assessment). As it turned out, all four pillars yielded some surprise. The aquifer consists of alluvial sediments, rather than coastal plain deposits. Tidal loading, rather than hydraulic connection to the sea, appears to drive tidal response, in spite of the aquifer being unconfined. Hydrochemistry suggests an unusually reactive layer, with all cations reflecting some mineral dissolution process, beyond the expected cation exchange. Radium increased with salinity, but the correlation was poor, partly blurred by pH, which was low in the deep portions of the aquifer. These observations were largely explained with the help of geophysics. Both borehole logs and cross-hole ERT helped in identifying silt layers that are frequent in alluvial deposits but proved to play a critical role here. The integration of the different techniques allowed to characterize the different distribution of salt- and freshgroundwater, that in fact yielded an inverse disposition to what is expected in coastal hydrogeology. To improve SGD quantification, we also characterized radium behavior within the aquifer. The recovered sediment during borehole drilling was used to perform both batch and column laboratory experiments. We performed constant salted fluid injections but we also vary the salinity (SWI and SGD simulation) to infer adsorbed Ra from its mobilization. Column experimens were later simulated using a 0D model to interpret the results. We have observed that heterogeneous flux through preferential flow paths occurs in the columns. Variations in these flow paths may explain the observed fluctuations. Such variations may also occur during the freshening and salinization experiments, but the changes in sorption are so dominant that overcome the impact of changes in porosity structure. La intrusión de agua de mar causa no solo la salinización de los acuíferos costeros, sino también una reducción en la descarga submarina de agua subterránea y en los flujos de nutrientes a los ecosistemas marinos.Carrera, JesúsConsejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]2021202120202021info:eu-repo/semantics/doctoralThesishttp://purl.org/coar/resource_type/c_db06http://hdl.handle.net/10261/230923reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)InglésSíinfo:eu-repo/semantics/openAccessoai:digital.csic.es:10261/2309232026-05-22T06:33:51Z
dc.title.none.fl_str_mv Characterization of seawater intrusion and submarine groundwater discharge in alluvial coastal aquifers: field and laboratory approach
title Characterization of seawater intrusion and submarine groundwater discharge in alluvial coastal aquifers: field and laboratory approach
spellingShingle Characterization of seawater intrusion and submarine groundwater discharge in alluvial coastal aquifers: field and laboratory approach
Martínez, Laura
title_short Characterization of seawater intrusion and submarine groundwater discharge in alluvial coastal aquifers: field and laboratory approach
title_full Characterization of seawater intrusion and submarine groundwater discharge in alluvial coastal aquifers: field and laboratory approach
title_fullStr Characterization of seawater intrusion and submarine groundwater discharge in alluvial coastal aquifers: field and laboratory approach
title_full_unstemmed Characterization of seawater intrusion and submarine groundwater discharge in alluvial coastal aquifers: field and laboratory approach
title_sort Characterization of seawater intrusion and submarine groundwater discharge in alluvial coastal aquifers: field and laboratory approach
dc.creator.none.fl_str_mv Martínez, Laura
author Martínez, Laura
author_facet Martínez, Laura
author_role author
dc.contributor.none.fl_str_mv Carrera, Jesús
Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]
description Aplicat embargament des de la data de defensa fins al 31 de desembre de 2020 Seawater intrusion (SWI) causes not only salinization of coastal aquifers, but also a reduction submarine groundwater discharge (SGD) and nutrient fluxes to marine ecosystems. We have developed a small scale experimental field site to gain insights into both SWI and SGD. The site is located in a coastal alluvial aquifer at the mouth of an ephemeral stream in the Maresme coastline (Barcelona, Spain). Here, we describe our attempts for a detailed site characterization, which was based on the four pillars of hydrogeology: geology (Lithological description and geochemical analysis of core), geophysics (borehole logs, Electrical Resistivity Tomography and thermal monitoring), hydraulics (pumping and tidal response tests) and hydrochemistry (major and minor elements, stable isotopes and Radium isotopes for SGD assessment). As it turned out, all four pillars yielded some surprise. The aquifer consists of alluvial sediments, rather than coastal plain deposits. Tidal loading, rather than hydraulic connection to the sea, appears to drive tidal response, in spite of the aquifer being unconfined. Hydrochemistry suggests an unusually reactive layer, with all cations reflecting some mineral dissolution process, beyond the expected cation exchange. Radium increased with salinity, but the correlation was poor, partly blurred by pH, which was low in the deep portions of the aquifer. These observations were largely explained with the help of geophysics. Both borehole logs and cross-hole ERT helped in identifying silt layers that are frequent in alluvial deposits but proved to play a critical role here. The integration of the different techniques allowed to characterize the different distribution of salt- and freshgroundwater, that in fact yielded an inverse disposition to what is expected in coastal hydrogeology. To improve SGD quantification, we also characterized radium behavior within the aquifer. The recovered sediment during borehole drilling was used to perform both batch and column laboratory experiments. We performed constant salted fluid injections but we also vary the salinity (SWI and SGD simulation) to infer adsorbed Ra from its mobilization. Column experimens were later simulated using a 0D model to interpret the results. We have observed that heterogeneous flux through preferential flow paths occurs in the columns. Variations in these flow paths may explain the observed fluctuations. Such variations may also occur during the freshening and salinization experiments, but the changes in sorption are so dominant that overcome the impact of changes in porosity structure. La intrusión de agua de mar causa no solo la salinización de los acuíferos costeros, sino también una reducción en la descarga submarina de agua subterránea y en los flujos de nutrientes a los ecosistemas marinos.
publishDate 2020
dc.date.none.fl_str_mv 2020
2021
2021
2021
dc.type.none.fl_str_mv info:eu-repo/semantics/doctoralThesis
http://purl.org/coar/resource_type/c_db06
format doctoralThesis
dc.identifier.none.fl_str_mv http://hdl.handle.net/10261/230923
url http://hdl.handle.net/10261/230923
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv Sí
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.source.none.fl_str_mv reponame:DIGITAL.CSIC. Repositorio Institucional del CSIC
instname:Consejo Superior de Investigaciones Científicas (CSIC)
instname_str Consejo Superior de Investigaciones Científicas (CSIC)
reponame_str DIGITAL.CSIC. Repositorio Institucional del CSIC
collection DIGITAL.CSIC. Repositorio Institucional del CSIC
repository.name.fl_str_mv
repository.mail.fl_str_mv
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