HAL will be down for maintenance from Friday, June 10 at 4pm through Monday, June 13 at 9am. More information
Skip to Main content Skip to Navigation
Journal articles

Autotrophic denitrification supported by biotite dissolution in crystalline aquifers: (2) transient mixing and denitrification dynamic during long-term pumping

Clément Roques 1, * Luc Aquilina 1 Alexandre Boisson 2 Virginie Vergnaud-Ayraud 1 Thierry Labasque 1 Laurent Longuevergne 1 Marc Laurencelle 3 Alexis Dufresne 4 Jean-Raynald de Dreuzy 1 Hélène Pauwels 2 Olivier Bour 1
* Corresponding author
1 GR - Géosciences Rennes
2 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
3 INRS - Institut National de la Recherche Scientifique [Québec]
4 ECOBIO - Ecosystèmes, biodiversité, évolution [Rennes]
Abstract : We investigated the mixing and dynamic of denitrification processes induced by long-term pumping in the crystalline aquifer of Ploemeur (Brittany, France). Hydrological and geochemical parameters have been continuously recorded over 15 boreholes in 5km(2) on a 25-year period. This extensive spatial and temporal monitoring of conservative as well as reactive compounds is a key opportunity to identify aquifer-scale transport and reactive processes in crystalline aquifers. Time series analysis of the conservative elements recorded at the pumped well were used to determine mixing fractions from different compartments of the aquifer on the basis of a Principal Component Analysis approach coupled with an end-member mixing analysis. We could reveal that pumping thus induces a thorough reorganization of fluxes known as capture, favoring infiltration and vertical fluxes in the recharge zone, and upwelling of deep and distant water at long-term time scales. These mixing fractions were then used to quantify the extent of denitrification linked to pumping. Based on the results from batch experiments described in a companion paper, our computations revealed that i) autotrophic denitrification processes are dominant in this context where carbon sources are limited, that ii) nitrate reduction does not only come from the oxidation of pyrite as classically described in previous studies analyzing denitrification processes in similar contexts, and that iii) biotite plays a critical role in sustaining the nitrate reduction process. Both nitrate reduction, sulfate production as well as fluor release ratios support the hypothesis that biotite plays a key role of electron donor in this context. The batch-to-site similarities support biotite availability and the role by bacterial communities as key controls of nitrate removal in such crystalline aquifers. However, the long term data monitoring also indicates that mixing and reactive processes evolve extremely slowly at the scale of the decade.
Keywords : Autotrophic denitrification Fractured aquifers Groundwater quality Kinetically-controlled reactions Mixing
Document type :
Journal articles
Complete list of metadata
https://hal-insu.archives-ouvertes.fr/insu-01653141
Contributor : Isabelle Dubigeon Connect in order to contact the contributor
Submitted on : Friday, December 1, 2017 - 9:56:06 AM
Last modification on : Monday, May 16, 2022 - 1:52:03 PM

Identifiers

Collections

INSU | CNRS | GR | UNIV-RENNES1 | BRGM | ECOBIO | GR-DIMENV | OSUR-OSU | OSUR | UR1-UFR-SVE | UNIV-RENNES | UR1-ENV | BRGM-DO | UR2-HB | UNIV-RENNES2 | INRAE

Citation

Clément Roques, Luc Aquilina, Alexandre Boisson, Virginie Vergnaud-Ayraud, Thierry Labasque, et al.. Autotrophic denitrification supported by biotite dissolution in crystalline aquifers: (2) transient mixing and denitrification dynamic during long-term pumping. Science of the Total Environment, Elsevier, 2018, 619-620, pp.491-503. ⟨10.1016/j.scitotenv.2017.11.104⟩. ⟨insu-01653141⟩

Export

BibTeX TEI DC DCterms EndNote Datacite

Share

Metrics

Record views

128