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Formació, cursos, Esdeveniments i Seminaris

LECTURA DE TESIS DOCTORAL: LAURA MARTINEZ PEREZ

Programa de doctorat: Enginyeria del Terreny

Nom del doctorand/a: LAURA MARTÍNEZ PÉREZ

Data de la defensa de tesi: 09/07/2020

Títol de la tesi doctoral: Characterization of seawater intrusion and submarine groundwater discharge in alluvial coastal aquifers: field and laboratory approach

Modalitat: Videoconferència

Enllaç videoconferència: https://meet.google.com/bzg-uhqo-jyi

Hora d’inici (hora local): 10:00 h

Abstract

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 fresh- groundwater, 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 experiments 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.

Ponencia: Dispersion upscaling in highly heterogeneous aquifers: The prediction of tracer dispersion at the Macrodispersion Experiment (MADE) site

Ciclo de webinars gratuitos en Hidrogeología y Geoquímica
TODOS LOS JUEVES en directo en: https://meet.google.com/snb-qdkn-eex   
 
Link de la presentación: Presentation_Dispersion_upscaling_1
GRUPO DE HIDROLOGÍA SUBTERRÁNEA
(Unidad asociada CSIC-UPC)

 

Esta semana: Jueves 02 de Julio a las 12:15h
 
Ponente: Marco Dentz. Profesor de Investigación CSIC
Ponencia: Dispersion upscaling in highly heterogeneous aquifers: The prediction of tracer dispersion at the Macrodispersion Experiment (MADE) site
Marco Dentz, Alessandro Comolli, Vivien Hakoun, and Juan Hidalgo
 
Abstract
We derive an upscaled model for the prediction of the plume evolution in highly heterogeneous aquifers based a stochastic transport representation in terms of continuous time random walks. Transport is modeled
through advective motion of idealized solute particles, which changes their speed at fixed distances. The series of particles speeds is modeled as a stationary Markov chain. The derived model is parameterized by the
correlation length, mean and variance of the log-hydraulic conductivity, the mean hydraulic gradient and porosity. Furthermore, it can be conditioned on the conductivity and tracer data at the injection region. 
The model predicts the main features of the non-Fickian evolution of the longitudinal concentration profile observed during the MADE-1 and MADE-2 experiments. The mass distribution is characterized by strong localization at the injection region and
a strong forward tail. These features are explained by heterogeneity of hydraulic conductivity heterogeneity, and the correlated motion of particles according to spatially persistent Lagrangian flow speeds.
 

Ponencia: A Matlab®-based toolbox for Geological Sequestration of CO2

Ciclo de webinars gratuitos en Hidrogeología y Geoquímica
 
 
TODOS LOS JUEVES en directo en: https://meet.google.com/snb-qdkn-eex   
Presentación on line: Yufei_Wang_Webinar
 
GRUPO DE HIDROLOGÍA SUBTERRÁNEA
(Unidad asociada CSIC-UPC)

 

Esta semana: Jueves 18 de Junio a las 12:15h
 
Ponente: Yufei Wang. PhD Student


Abstract:
Carbon Capture and Sequestration (CCS) is a feasible technique to mitigate the global climate change due to temperature increase. This
research focuses on geological CO2 sequestration. A Matlab®-based toolbox is developed to simulate the CO2-Brine system during the
injection of supercritical CO2 into subsurface saline formation. In the process, we consider the evaporation of H2O into CO2-rich phase as well
as the dissolution of CO2 into the brine phase. The numerical model is thus a Compressible-Reactive Two-phase flow model.
This seminar concentrates on how to build the numerical model and how to solve the numerical model. Detailed information, such as constitution
equations, will be discussed. Some methods  for improving on the numerical solution are proposed. Some preliminary results will be shown
 
 

Webinar: Where do Rare Earth Elements spend the summer?

TODOS LOS JUEVES en directo en: https://meet.google.com/snb-qdkn-eex   

Visualización de la presentación: Carlos Ayora_Webinar

GRUPO DE HIDROLOGÍA SUBTERRÁNEA

(Unidad asociada CSIC-UPC)

 Esta semana: Jueves 11 de Junio a las 12:15h

Ponente: CARLOS AYORA IBAÑEZ. Profesor de Investigación CSIC

Ponencia: Where do Rare Earth Elements spend the summer?

Abstract:
Acid mine drainages (AMD) are very enriched in Rare Earth Elements (REE) compared with other natural waters. The REE remain in solution until the acid stream is neutralized in treatment systems or by mixing with an alkaline river or the ocean. In the dry season of Mediterranean climates, acid streams dry off leaving behind a mixture of efflorescent sulfate salts. The fate of REE during evaporation was investigated by sampling and analyses of sulfates resulting from six AMD samples, and the principal component analysis (PCA) of the results. Light REE were clearly related to Ca (PCA1) whereas Heavy REE seemed associated with Al (PCA2). On the contrary, no relationship was found with Fe and Mg sulfates (PCA3). The REE distribution between PCA1 and PCA2 matches beautifully the ionic radius of each ion in the octahedral configuration. It is, therefore, initially concluded that Light REE replace Ca in gypsum, whereas Heavy REE might replace Al in alunogen, although in progress experiments must confirm/deny this conclusion. The results could be relevant to concentrate REE from AMD with very soft chemistry.

Lectura de Tesis: Advancing in the characterization of coastal aquifers

PONENTE: LAURA DEL VAL (PHD STUDENT)

Subtitulo tesis: A multimethodological approach based on Fiber Optics Distributed Temperature Sensing

 

Fecha/ Hora defensa: Miércoles 3 de Junio a las 4:00pm

 

Link en Google Meet: https://meet.google.com/jod-wyna-nve

 

Abstract

Detailed characterization of coastal aquifers is essential for proper management of coastal groundwater resources, and coastal areas in general. Still, there is a general lack of systematic monitoring and detailed characterization of the seawater intrusion (SWI). This thesis aims to provide new approaches and methodologies for the characterization of coastal aquifers, and in particular for the SWI dynamics.

At a first stage, a new coastal experimental site was constructed in the Riera de Argentona,  40km North from Barcelona. Three relatively new monitoring systems were tested to characterize the SWI in this site: Cross-Hole Electric Resistivity Tomography (CHERT), Time Laps Induction Logging (TLIL) and Fiber Optics Distributed Temperature Sensing (FO-DTS).  From these techniques we were interested in further exploring the use of FO-DTS in a coastal setting. First, an active FO-DTS application to measure groundwater fluxes is proposed. This was done by interpreting the temperature curves generated by heating a single FO cable and measuring the temperature evolution in the same cable. Second, the use of FO-DTS passively, thus by measuring natural temperature changes, is proposed to monitor the SWI. Before field testing, the use of temperature as a tracer of the SWI was studied theoretically. To do this, two numerical models were used to explore the coupled behavior of temperature and solutes at the fresh-salt water interface. Based on the results from the modelling exercise and the conceptual framework resulting from it, FO-DTS was tested for continuously monitoring of the SWI during one year and a half. In parallel, an alternative methodology is proposed to remove environmental trends and noise from measured groundwater heads resulting from pumping tests carried out in coastal aquifers.

The set of methods proposed in this thesis expands the tools and the resolution available to characterize the SWI, contributing to improve our knowledge about coastal aquifers.

 

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