Chemical weathering and CO2 consumption in a multi-lithological karstic critical zone: Long term hydrochemical trends and isotopic survey

Autor: Anne Probst, F. Ulloa-Cedamanos, Jean-Luc Probst, Issam Moussa
Přispěvatelé: Laboratoire Ecologie Fonctionnelle et Environnement (ECOLAB), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique - CNRS (FRANCE), Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE), Université Toulouse III - Paul Sabatier - UT3 (FRANCE), Laboratoire Ecologie Fonctionnelle et Environnement (LEFE), Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT), Service National d'Observation sur le KARST (SNO Karst), Institut national des sciences de l'Univers (INSU - CNRS), Zone Atelier Pyrénées-Garonne (ZA PYGAR), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoires de la zone critique - OZCAR (FRANCE)
Jazyk: angličtina
Rok vydání: 2021
Předmět:
Seasonal patterns
010504 meteorology & atmospheric sciences
Weathering
[SDE.MCG]Environmental Sciences/Global Changes
Geochemistry
δ13CDIC and δ34SSO4
Karst
Mixing diagrams
Long-term hydrochemical survey
010501 environmental sciences
[SDV.SA.SDS]Life Sciences [q-bio]/Agricultural sciences/Soil study
01 natural sciences
Carbon cycle
Mountainous forested catchment
Isotopic signature
chemistry.chemical_compound
[SDV.EE.ECO]Life Sciences [q-bio]/Ecology
environment/Ecosystems
Geochemistry and Petrology
[SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry
Carbonate dissolution
[SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology
[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces
environment
ComputingMilieux_MISCELLANEOUS
0105 earth and related environmental sciences
Calcite
Carbonic acid
Ecologie
Environnement
geography
geography.geographical_feature_category
[SDE.IE]Environmental Sciences/Environmental Engineering
Geology
15. Life on land
chemistry
13. Climate action
Carbonate
[SDV.TOX.ECO]Life Sciences [q-bio]/Toxicology/Ecotoxicology
[SDE.BE]Environmental Sciences/Biodiversity and Ecology
Surface runoff
Zdroj: Chemical Geology
Chemical Geology, 2021, pp.120567. ⟨10.1016/j.chemgeo.2021.120567⟩
Chemical Geology, 2021, 585, pp.120567. ⟨10.1016/j.chemgeo.2021.120567⟩
ISSN: 0009-2541
DOI: 10.1016/j.chemgeo.2021.120567⟩
Popis: The chemical weathering (CW) of rocks at the Earth's surface plays a key role in the global carbon cycle along multiple pathways. Although karst systems are hotspot carbonated areas, they are not always monolithological. It is therefore challenging to estimate the CW of these complex areas. The interannual, seasonal, and spatial variations of CW rates and CO2 consumption were investigated using a long-term hydrogeochemical database (1994–2019) from a mountainous karstic catchment in southwestern France (Baget Catchment). A geochemical and isotopic spatial sampling allowed the identification of the main mineral or lithological sources in the catchment, which controlled the water chemistry. The CW budget showed that the (Ca2+ + Mg2+) fluxes originated from carbonate dissolution (1.14 mol·m−2·yr−1 equivalent to 74%) and silicate weathering (18%) by carbonic acid solutions. Gypsum dissolution and carbonate weathering by sulphuric acid from pyrite oxidation contribute equally to 4%, although the former accounts for 66% of the dissolved sulphate fluxes. During a summer sampling survey, an innovative sulphur isotopic approach based on δ34SSO4, allowed us to demonstrate that the ore-nature sulphuric acid drove 9.0% of total carbonate dissolution and represented only 16.8% of the dissolved sulphate stream fluxes. Hydrological conditions, temperature, vegetation, the epikarst (quasi-permanent shallow and discontinuous saturated layer under the soil), and the water dynamics were the key factors influencing the inter-annual and inter-seasonal variations of the CW rates and CO2 consumption. In addition, the carbon isotopic signature evidenced geochemical processes such as CO2 outgassing and calcite precipitation processes. The latter could remove up to 74% of HCO3− from streamwaters, depending on the hydrological conditions at the outlet between 2016 and 2019. Finally, this study highlights that CW rates and CO2 consumption may vary over inter-annual and inter-seasonal scales, and spatially even for a small catchment. Furthermore, the global CO2 consumption appears to be mainly driven by the runoff intensity in karst hydrosystems, where carbonate dissolution was found to consume 71% of the total weathering CO2 uptake.
Databáze: OpenAIRE
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