The potential of major ion chemistry to assess groundwater vulnerability of a regional aquifer in southern Quebec (Canada)

Meyzonnat, G.; Larocque, M.; Barbecot, F.; Pinti, D. L. et Gagné, S. (2016). « The potential of major ion chemistry to assess groundwater vulnerability of a regional aquifer in southern Quebec (Canada) ». Environmental Earth Sciences, 75(68), pp. 1-12.

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Résumé

Groundwater vulnerability mapping provides useful but limited information for developing protection plans of the resource. Classical vulnerability ranking methods often do not take into account complex hydrostratigraphy and never consider groundwater flow dynamics. The objective of this work was to test the potential of major ion chemistry to assess regional-scale intrinsic groundwater vulnerability. Because it reflects water–sediment and water–rock interactions, the new vulnerability index reflects both infiltration processes and groundwater hydrodynamics. The method was applied on a regional fractured bedrock aquifer located in the Becancour region of southern Quebec (Canada). In this region, hydrogeochemistry shows that freshly recharged groundwater evolves from (Ca, Mg)–HCO3 and Ca–SO4 to Na–HCO3 type with gradually increasing confinement conditions in the fractured aquifer and tends to Na–Cl type locally by mixing with trapped marine pore-water. The new method identified recharge areas as those of the highest vulnerability and gradually decreasing vulnerability as confinement of the aquifer increased. It also highlights local discontinuities in confinement that differ from the regional pattern. Results showed a good correlation between groundwater vulnerability estimated with the new method and nitrate occurrence in groundwater. Eighty-two per cent of all samples presenting detectable nitrate concentrations were characterized by a Hydrogeochemical Vulnerability Index greater than 9 (maximum is 10). The ability of the new vulnerability method to identify areas vulnerable to detectable nitrate concentrations was much higher than that deriving from the DRASTIC method. This work confirms that major ions chemistry contains significant information about groundwater vulnerability and could be used to improve groundwater resource management.

Type:	Article de revue scientifique
Informations complémentaires:	The final publication is available at Springer via http://dx.doi.org/10.1007/s12665-015-4793-9
Mots-clés ou Sujets:	Groundwater, vulnerability, hydrogeochemistry, fractured bedrock aquifer, Quebec (Canada)
Unité d'appartenance:	Centres institutionnels > Centre de recherche en géochimie et géodynamique (GEOTOP) Faculté des sciences > Département des sciences de la Terre et de l'atmosphère
Déposé par:	Marie Larocque
Date de dépôt:	23 mars 2016 13:15
Dernière modification:	20 mars 2020 13:14
Adresse URL :	http://archipel.uqam.ca/id/eprint/8005

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