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9. Channel cross-section heterogeneity of particulate organic carbon transport in the Huanghe.

Author

Ke, Yutian, Calmels, Damien, Bouchez, Julien, Massault, Marc, Chetelat, Benjamin, Noret, Aurélie, Cai, Hongming, Chen, Jiubin, Gaillardet, Jérôme, and Quantin, Cécile

Subjects
COLLOIDAL carbon, CARBON cycle, FLUVIAL geomorphology, SOIL horizons, WATERSHEDS, HETEROGENEITY, PLAINS
Abstract

The Huanghe (Yellow River), one of the largest turbid river systems in the world, has long been recognized as a major contributor of suspended particulate matter (SPM) to the ocean. However, over the last few decades, the SPM export flux of the Huanghe has decreased over 90 % due to the high management, impacting the global export of particulate organic carbon (POC). To better constrain sources and modes of transport of POC beyond the previously investigated transportation of POC near the channel surface, SPM samples were for the first time collected over a whole channel cross-section in the lower Huanghe. Riverine SPM samples were analyzed for particle size and major element contents, as well as for POC content and dual carbon isotopes (13C and 14C). Clear vertical and lateral heterogeneities of the physical and chemical properties of SPM are observed within the river cross-section. For instance, finer SPM carry more POC in general with higher 14C activity near the surface of the right bank. Notably, we discuss how bank erosion in the alluvial plain is likely to generate lateral heterogeneity in POC composition. The Huanghe POC is millennial-aged (4020 ± 500 radiocarbon years) and dominated by organic carbon (OC) from the biosphere, while the lithospheric fraction is ca. 12 %. The mobilization of aged and refractory OC, including radiocarbon-dead biospheric OC, from deeper soil horizons of the loess–paleosol sequence through erosion in the Chinese Loess Plateau is an important mechanism contributing to fluvial POC in the Huanghe drainage basin. Altogether, anthropogenic activities can drastically change the compositions and transport dynamics of fluvial POC, consequentially altering the feedback of the source-to-sink trajectory of a river system to regional and global carbon cycles. [ABSTRACT FROM AUTHOR]

Published
2024
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10. Channel cross-section heterogeneity of particulate organic carbon transport in the Huanghe

Author

Ke, Yutian, Calmels, Damien, Bouchez, Julien, Massault, Marc, Chetelat, Benjamin, Noret, Aurélie, Cai, Hongming, Chen, Jiubin, Gaillardet, Jérôme, and Quantin, Cécile

Abstract

The Huanghe (Yellow River), one of the largest turbid river systems in the world, has long been recognized as a major contributor of suspended particulate matter (SPM) to the ocean. However, over the last few decades, the SPM export flux of the Huanghe has decreased over 90 % due to the high management, impacting the global export of particulate organic carbon (POC). To better constrain sources and modes of transport of POC beyond the previously investigated transportation of POC near the channel surface, SPM samples were for the first time collected over a whole channel cross-section in the lower Huanghe. Riverine SPM samples were analyzed for particle size and major element contents, as well as for POC content and dual carbon isotopes (13C and 14C). The results show clear vertical and lateral heterogeneity of SPM physical and chemical characteristics within the river cross-section, with for example finer SPM carrying more POC with higher 14C activity near the surface of the right bank. Notably, we discuss how bank erosion in the alluvial plain is likely to generate lateral heterogeneity in POC composition. The Huanghe POC is millennial-aged (4,020 ± 500 radiocarbon years), dominated by organic carbon (OC) from the biosphere, while the lithospheric fraction reaches up to ca. 33 %. The mobilization of aged and refractory OC, including radiocarbon-dead biospheric OC, from deeper soil horizons of the loess-paleosol sequence through erosion in the Chinese Loess Plateau is an important mechanism contributing to fluvial POC in the Huanghe drainage basin. Altogether, anthropogenic activities can drastically change the compositions and transport dynamics of fluvial POC, consequentially altering the feedback of the source-to-sink trajectory of a river system to regional and global carbon cycles.

Published
2023

14. Bilan hydrologique d'un système aquifère surexploité en région désertique : estimation de la recharge et paléorecharge par couplage d'approches satellitaires et géochimiques

Author

Deschamps, Pierre, Séraphin, Pierre, Khabouchi, Imen, Gonçalvès, Julio, Stieglitz, Thomas, Michelot, Jean-Luc, Noret, Aurélie, Gibert, E., Aquilina, Luc, Labasque, Thierry, Hamelin, Bruno, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Aix Marseille Université (AMU), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Géosciences Paris Sud (GEOPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Géosciences Paris Saclay (GEOPS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), and Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.STU]Sciences of the Universe [physics]/Earth Sciences
Abstract

International audience; Partagé entre la Jordanie et l'Arabie saoudite, le système aquifère du Saq-Ram (520 000 km²) constitue l'une des principales ressources en eau de la péninsule arabique. Largement exploité depuis les années 80 pour soutenir le développement d'une agriculture irriguée intensive, cet aquifère multicouche, principalement gréseux, est aujourd'hui un des systèmes aquifères les plus surexploités au monde, caractérisé par des cônes de rabattement de plusieurs centaines de kilomètres. Afin d'évaluer la durabilité de cette ressource aquifère, le projet WAO (Past, present and future Water resources in Al-Ula Oasis) combine méthodes satellitaires et géochimiques pour contraindre les différentes composantes du bilan hydrique de l'hydrosystème : prélèvements, recharge-actuelle et passée-, retour d'irrigation… A l'échelle régionale, les données satellitaires gravimétriques (GRACE) ont permis de contraindre les variations du stock d'eau souterraine pour la période 2002-2019. En s'appuyant sur une estimation des prélèvements des eaux souterraines, de la recharge artificielle (principalement liée aux excédents d'irrigation) et des sorties naturelles du système, le calcul du bilan hydrologique dérivé de GRACE donne une estimation moyenne de la recharge naturelle sur les deux dernières décennies de 1,6 ± 1,2 mm.an-1 pour l'ensemble du Saq-Ram, correspondant à 2,9 ± 2,2% de la pluviométrie moyenne interannuelle (i.e. 55 mm.an-1). Ce taux de recharge est nettement supérieur à ceux d'aquifères arides sahariens similaires (i.e. 1,7 ± 1,2% des pluies), obtenus avec la même approche gravimétrique. Une explication plausible est que les plateaux volcaniques qui couvrent une surface conséquente du système aquifère du Saq-Ram favorisent l'infiltration des eaux pluviales. Ne couvrant que 8 % du domaine du Saq-Ram, ces massifs basaltiques contribueraient à environ 40 % de la recharge naturelle totale. Pour conforter/confronter ces résultats obtenus à l'échelle du système Saq-Ram, une étude a été menée plus localement sur une zone de recharge située dans la région d'Al Ula. Un large panel d'outils géochimiques (majeurs, gaz anthropiques (CFCs, SF 6) et nobles (Ne, Ar)) et isotopiques (dD, d 18 O, 14 C, 36 Cl, 87 Sr/ 86 Sr) a été déployé pour déterminer l'origine (naturelle ou artificielle) et l'âge de la recharge de l'aquifère du Saq-Ram et des aquifères alluviaux de la région. Si les traceurs comme les CFCs et SF 6 ou 36 Cl indiquent une recharge active pour les aquifères alluviaux, les traces d'une recharge récente du Saq-Ram dans cette zone restent peu évidentes, d'autant plus que les retours d'irrigation, aisément tracés par l'augmentation de la salinité, sont bien visibles dans les eaux souterraines prélevées au droit des zones agricoles. Les seules traces de recharge récente sont données par la composition isotopique des eaux des sources qui sourdent au contact entre les grès et le plateau basaltique qui surplombe la vallée d'Al Ula. Leur composition est marquée par un mélange entre les précipitations actuelles et les eaux du Saq-Ram dont la signature est significativement appauvrie. Cette signature très distincte des eaux du Saq-Ram indique une recharge lors de périodes caractérisées par un régime de précipitations distinct de l'actuel. La présence de 14 C dans tous les échantillons et la relative constance du rapport (36 Cl/Cl), preuve de l'absence de décroissance significative de ce radionucléide, permettent de restreindre cette recharge très probablement à la période humide africaine holocène.

Published
2022

19. Datation des phases critiques de fracturation et caractérisation des fluides au cours de l'évolution du prisme alpin

Author

Bilau, Antonin, Rolland, Yann, Schwartz, Stephane, Godeau, Nicolas, Guihou, Abel, Deschamps, Pierre, Gautheron, Cécile, Pinna-Jamme, Rosella, Mangenot, Xavier, Brigaud, Benjamin, Noret, Aurélie, Dumont, Thierry, Sciencesconf.org, CCSD, Environnements, Dynamiques et Territoires de Montagne (EDYTEM), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre (ISTerre), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Gustave Eiffel-Université Grenoble Alpes (UGA), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Géosciences Paris Saclay (GEOPS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), California Institute of Technology (CALTECH), and SGF, CNRS, Laboratoire de Géologie de Lyon ou l’étude de la Terre, des planètes et de l’environnement

Subjects
Inversion Front Pennique, δ13C, [SDU] Sciences of the Universe [physics], Datations, (U, [SDU]Sciences of the Universe [physics], Failles, Pb calcite, Th, Sm)/He hématite, Isotopie stable, δ18O, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2021

21. Timing of fault gouge formation and fluid-rock interaction during tectonic inversion of the Penninic Frontal Thrust (SW Alps)

Author

Bilau, Antonin, primary, Rolland, Yann, additional, Schwartz, Stéphane, additional, Godeau, Nicolas, additional, Guihou, Abel, additional, Deschamps, Pierre, additional, Gautheron, Cécile, additional, Pinna-Jamme, Rosella, additional, Brigaud, Benjamin, additional, Mangenot, Xavier, additional, Noret, Aurélie, additional, Melleton, Jérémie, additional, and Dumont, Thierry, additional

Published
2021
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24. Supplementary material to "Extensional reactivation of the Penninic Frontal Thrust 3 Ma ago as evidenced by U-Pb dating on calcite in fault zone cataclasite"

Author

Bilau, Antonin, primary, Rolland, Yann, additional, Schwartz, Stéphane, additional, Godeau, Nicolas, additional, Guihou, Abel, additional, Deschamps, Pierre, additional, Brigaud, Benjamin, additional, Noret, Aurélie, additional, Dumont, Thierry, additional, and Gautheron, Cécile, additional

Published
2020
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26. Using Water Stable Isotopes in the Unsaturated Zone to Quantify Recharge in Two Contrasted Infiltration Regimes

Author

Barbecot, Florent, Guillon, Sophie, Pili, Eric, Larocque, Marie, Gibert-Brunet, Elisabeth, Hélie, Jean-François, Noret, Aurélie, Plain, Caroline, Schneider, Vincent, Mattei, Alexandra, Meyzonnat, Guillaume, Barbecot, Florent, Guillon, Sophie, Pili, Eric, Larocque, Marie, Gibert-Brunet, Elisabeth, Hélie, Jean-François, Noret, Aurélie, Plain, Caroline, Schneider, Vincent, Mattei, Alexandra, and Meyzonnat, Guillaume

Abstract

A reliable estimate of recharge is needed for the sustainable management of groundwater resources. Water stable isotope (δ18O and δ2H) profiles in the unsaturated zone are frequently used to quantify groundwater recharge based on the seasonality of water isotopic compositions in precipitation. A very simple approach consists of integrating the soil water content between peak values of soil water isotopic composition, typically corresponding to precipitation signatures from warm and cold seasons. When precipitation isotopic compositions are available, a conceptual surface water isotopes budget and lumped parameter dispersion model can be computed. These models were applied on two field sites with similar permeable soils with grass cover but contrasting recharge regimes and seasonality, one in the Paris Basin (France) with continuous recharge from autumn to spring and the other in the St. Lawrence Lowlands (Quebec, Canada) with episodic recharge in fall and after snowmelt. For the two sites, the peak-to-peak method and isotope surface budget led to comparable recharge intensities. At least at the Paris Basin site, evaporation was shown to slightly modify the average unsaturated zone and hence groundwater isotope composition. The proposed parameterization of isotope fractionation due to evaporation allows qualitative estimation of the fraction of evaporation, at least during the recharge seasons. In spite of its simplifications and limitations, the proposed parsimonious model can give estimates of recharge in a variety of sites even if they are not well characterized, as it benefits from the large availability of monthly isotopic compositions in precipitation.

Published
2018

27. Interactions between groundwater and seasonally ice-covered lakes: using water stable isotopes and radon-222 multi-layer mass balance models

Author

Arnoux, Marie, Gibert-Brunet, E., Barbecot, Florent, Guillon, Sophie, Gibson, John, Noret, Aurélie, Centre de recherche en géochimie et géodynamique (GEOTOP ), Université du Québec à Montréal = University of Québec in Montréal (UQAM), Géosciences Paris Sud (GEOPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Centre de Géosciences (GEOSCIENCES), MINES ParisTech - École nationale supérieure des mines de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)

Subjects
[SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2017
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28. Extensional reactivation of the Penninic Frontal Thrust 3 Ma ago as evidenced by U-Pb dating on calcite in fault zone cataclasite.

Author

Bilau, Antonin, Rolland, Yann, Schwartz, Stéphane, Godeau, Nicolas, Guihou, Abel, Deschamps, Pierre, Brigaud, Benjamin, Noret, Aurélie, Dumont, Thierry, and Gautheron, Cécile

Subjects
CALCITE, PERCOLATION, GEOMORPHOLOGY, MORPHOTECTONICS, THRUST belts (Geology)
Abstract

In the Western Alps, the Penninic Frontal Thrust (PFT) is the main crustal-scale tectonic structure of the belt. This thrust transported the high-pressure metamorphosed internal units over the un-metamorphosed European margin during the Oligocene (34-29 Ma). The PFT was later reactivated as an extensional detachment associated with the development of the High- Durance extensional fault system. This inversion of tectonic motions on a major tectonic structure has been widely emphasized as an example of extensional collapse of a thickened collisional orogen. However, the inception age of the extensional inversion remains unconstrained. Here, for the first time, we provide chronological constraints on the extensional motion of an exhumed zone of the PFT by applying U-Pb dating on secondary calcites from a fault zone cataclasite. The calcite cement of the cataclasite, formed after the main fault slip event, is dated at 3.4 ± 1.5 Ma. Cross-cutting calcite veins featuring the last fault motions are dated at 2.6 ± 0.3 and 2.3 ± 0.3 Ma. d13C and d18O fluid signatures derived from these secondary calcites suggest fluid percolation from deep-seated reservoir at the scale of the Western Alps. Our data give evidence that the PFT extensional reactivation is active since at least ~ 3 Ma, at the crustal scale and results from the westward propagation of the compressional deformation related to the exhumation of External Crystalline Massifs. In this context, the exhumation of the dated extensional fault is associated with the eastward translation of the seismogenic zone controlled by the deep rooting of the High-Durance fault system. [ABSTRACT FROM AUTHOR]

Published
2020
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29. A Newly Designed Analytical Line to Examine Fluid Inclusion Isotopic Compositions in a Variety of Carbonate Samples

Author

Dassié, Emilie P., primary, Genty, Dominique, additional, Noret, Aurélie, additional, Mangenot, Xavier, additional, Massault, Marc, additional, Lebas, Nicolas, additional, Duhamel, Maxence, additional, Bonifacie, Magali, additional, Gasparrini, Marta, additional, Minster, Benedicte, additional, and Michelot, Jean-Luc, additional

Published
2018
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31. Using Water Stable Isotopes in the Unsaturated Zone to Quantify Recharge in Two Contrasted Infiltration Regimes

Author

Barbecot, Florent, primary, Guillon, Sophie, additional, Pili, Eric, additional, Larocque, Marie, additional, Gibert-Brunet, Elisabeth, additional, Hélie, Jean-François, additional, Noret, Aurélie, additional, Plain, Caroline, additional, Schneider, Vincent, additional, Mattei, Alexandra, additional, and Meyzonnat, Guillaume, additional

Published
2018
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35. Water balance estimates of the Austre Lovén glacier catchment (western coast of Spitsbergen, Svalbard)

Author

Quenet , Mélanie, Marlin , Christelle, Griselin , Madeleine, Tolle , Florian, Friedt , Jean-Michel, Bernard , Eric, Saintenoy , Albane, Noret , Aurélie, Monvoisin , Gaël, Géosciences Paris Sud ( GEOPS ), Université Paris-Sud - Paris 11 ( UP11 ) -Centre National de la Recherche Scientifique ( CNRS ), Théoriser et modéliser pour aménager ( ThéMA ), Université de Bourgogne ( UB ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Franche-Comté ( UFC ), Franche-Comté Électronique Mécanique, Thermique et Optique - Sciences et Technologies ( FEMTO-ST ), and Université de Technologie de Belfort-Montbeliard ( UTBM ) -Ecole Nationale Supérieure de Mécanique et des Microtechniques ( ENSMM ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Franche-Comté ( UFC )

Subjects
water balance, glacier, [ SDU.STU ] Sciences of the Universe [physics]/Earth Sciences, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2015

36. Contamination sur le long terme

Author

Gasperi, Johnny, Ayrault, Sophie, Moreau-Guigon, Elodie, Tran, Bich Chau, Marie-Jeanne, Teil, Blanchard, Martine, Alliot, Fabrice, Chevreuil, Marc, Cladière, Mathieu, Tassin, Bruno, Bonhomme, Céline, Vilmin, Lauriane, Flipo, Nicolas, Surchamp, Alexia, Labadie, Pierre, Simonnet-Laprade, Caroline, Bourges, Catherine, Desportes, Annie, Budzinski, Hélène, Caupos, Emilie, Moilleron, Régis, Le Pape, Pierre, Michelot, Jean-Luc, Monvoisin, Gaël, Bordier, Louise, Noret, Aurélie, Quantin, Cécile, Bonnot, Caroline, Louvat, Pascale, Morin, Guillaume, Rocher, Vincent, Kieffer, Isabelle, Proux, Olivier, Benedetti, Marc, and Gelabert, Alexandre

Published
2015
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37. Origin of groundwater salinity (current seawater vs. saline deep water) in a coastal karst aquifer based on Sr and Cl isotopes. Case study of the La Clape massif (southern France)

Author

Khaska, Mahmoud, Le Gal La Salle, Corinne, Lancelot, Joël, Mohamad, Amad, Verdoux, Patrick, Noret, Aurélie, Simler, Roland, Aster, Team, Arnold, M., BOURLÈS, D., Keddadouche, K., Aumaitre, Georges, Laboratoire GIS, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), École supérieure du professorat et de l'éducation - Lille Nord de France (ESPE LNF), Université Lille Nord de France (COMUE), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), Laboratoire de Géochimie Isotopique Environnementale (GIS) / Université de Nîmes (GIS), Université de Nîmes (UNIMES)-Centre National de la Recherche Scientifique (CNRS), Géosciences Paris Sud (GEOPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Hydrogéologie d'Avignon (LHA), Avignon Université (AU), Détection, évaluation, gestion des risques CHROniques et éMErgents (CHROME) / Université de Nîmes (CHROME), Université de Nîmes (UNIMES), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Lattaquié Dpt of Geology, University of Tichrine, Environnement Méditerranéen et Modélisation des Agro-Hydrosystèmes (EMMAH), Avignon Université (AU)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), this study was funded by the University of Nimes within the framework of its research program 'Transdisciplinary approach of environmental risks', which was partially supported by the General Council of the Gard Department and the Greater Nimes Metropole. The French AMS national facility ASTER (CEREGE, Aix en Provence) is supported by INSU/CNRS, the French Ministry of Research and Higher Education, IRD and CEA, Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Evaporite, 0207 environmental engineering, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Aquifer, 02 engineering and technology, 010501 environmental sciences, 01 natural sciences, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Geochemistry and Petrology, Environmental Chemistry, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, 020701 environmental engineering, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, salinité, Hydrology, geography, geography.geographical_feature_category, Brackish water, Groundwater recharge, Saline water, Karst, Pollution, 6. Clean water, 13. Climate action, Aquifère côtier, calcaire crétacé, [SDE]Environmental Sciences, analyse isotopique, Seawater, analyse géochimique, Groundwater, Geology
Abstract

International audience; Origin of groundwater salinity (current seawater vs. saline deep water) in a coastal karst aquifer based on Sr and Cl isotopes. Case study of the La Clape massif (southern France) a b s t r a c t In this study a typical coastal karst aquifer, developed in lower Cretaceous limestones, on the western Med-iterranean seashore (La Clape massif, southern France) was investigated. A combination of geochemical and isotopic approaches was used to investigate the origin of salinity in the aquifer. Water samples were collected between 2009 and 2011. Three groundwater groups (A, B and C) were identified based on the hydrogeological setting and on the Cl À concentrations. Average and maximum Cl À concentrations in the recharge waters were calculated (Cl Ref. and Cl Ref.Max) to be 0.51 and 2.85 mmol/L, respectively). Group A includes spring waters with Cl À concentrations that are within the same order of magnitude as the Cl Ref concentration. Group B includes groundwater with Cl À concentrations that range between the Cl Ref and Cl Ref.Max concentrations. Group C includes brackish groundwater with Cl À concentrations that are significantly greater than the Cl Ref.Max concentration. Overall, the chemistry of the La Clape groundwater evolves from dominantly Ca–HCO 3 to NaCl type. On binary diagrams of the major ions vs. Cl, most of the La Clape waters plot along mixing lines. The mixing end-members include spring waters and a saline component (current seawater or fossil saline water). Based on the Br/Cl molar ratio, the hypothesis of halite dissolution from Triassic evaporites is rejected to explain the origin of salinity in the brackish groundwater. Groundwaters display 87 Sr/ 86 Sr ratios intermediate between those of the limestone aquifer matrix and current Mediterranean seawater. On a Sr mixing diagram, most of the La Clape waters plot on a mixing line. The end-members include the La Clape spring waters and saline waters, which are similar to the deep geo-thermal waters that were identified at the nearby Balaruc site. The 36 Cl/Cl ratios of a few groundwater samples from group C are in agreement with the mixing hypothesis of local recharge water with deep saline water at secular equilibrium within a carbonate matrix. Finally, PHREEQC modelling was run based on cal-cite dissolution in an open system prior to mixing with the Balaruc type saline waters. Modelled data are consistent with the observed data that were obtained from the group C groundwater. Based on several trac-ers (i.e. concentrations and isotopic compositions of Cl and Sr), calculated ratios of deep saline water in the mixture are coherent and range from 3% to 16% and 0% to 3% for groundwater of groups C and B, respectively. With regard to the La Clape karst aquifer, the extension of a lithospheric fault in the study area may favour the rise of deep saline water. Such rises occur at the nearby geothermal Balaruc site along another lithospheric fault. At the regional scale, several coastal karst aquifers are located along the Gulf of Lion and occur in Mezosoic limestones of similar ages. The 87 Sr/ 86 Sr ratios of these aquifers tend toward values of 0.708557, which suggests a general mixing process of shallow karst waters with deep saline fossil waters. The occurrence of these fossil saline waters may be related to the introduction of seawater during and after the Flandrian transgression, when the highly karstified massifs invaded by seawater, formed islands and peninsulas along the Mediterranean coast.

Published
2013
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