Linking groundwater quality to residence times and regional geology in the St. Lawrence Lowlands, southern Quebec, Canada
The assessment of groundwater quality in shallow aquifers is of high societal relevance given that large populations depend directly on these water resources. The purpose of this study was to establish links between groundwater quality, groundwater residence times, and regional geology in the St. La...
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ftunivquebec:oai:www.archipel.uqam.ca:8010 2023-05-15T16:41:02+02:00 Linking groundwater quality to residence times and regional geology in the St. Lawrence Lowlands, southern Quebec, Canada Saby, Marion Larocque, Marie Pinti, Daniele L. Barbecot, Florent Sano, Yuji Castro, Maria Clara 2016-02 application/pdf http://archipel.uqam.ca/8010/1/Saby%20et%20al%20%282015%29%20Applied%20Geochemistry.pdf en eng http://archipel.uqam.ca/8010/ http://dx.doi.org/10.1016/j.apgeochem.2015.10.011 doi:10.1016/j.apgeochem.2015.10.011 Groundwater quality Groundwater residence times Regional geology St. Lawrence Lowlands Quebec (Canada) Article de revue scientifique PeerReviewed 2016 ftunivquebec https://doi.org/10.1016/j.apgeochem.2015.10.011 2018-04-07T23:04:54Z The assessment of groundwater quality in shallow aquifers is of high societal relevance given that large populations depend directly on these water resources. The purpose of this study was to establish links between groundwater quality, groundwater residence times, and regional geology in the St. Lawrence Lowlands fractured bedrock aquifer. The study focuses on a 4500 km2 watershed located in the St. Lawrence Lowlands of the province of Quebec in eastern Canada. A total of 150 wells were sampled for major, minor, and trace ions. Tritium (3H) and its daughter element, 3He, as well as radiocarbon activity (A14C) were measured in a subset of wells to estimate groundwater residence times. Results show that groundwater evolves from a Ca–HCO3 water type in recharge zones (i.e., the Appalachian piedmont) to a Na–HCO3 water type downgradient, toward the St. Lawrence River. Locally, barium (Ba), fluoride (F), iron (Fe), and manganese (Mn) concentrations reach 90, 2, 18, and 5.9 mg/L respectively, all exceeding their respective Canadian drinking water limits of 1, 1.5, 0.3, and 0.05 mg/L. Release of these elements into groundwater is mainly controlled by the groundwater redox state and pH conditions, as well as by the geology and the duration of rock–water interactions. This evolution is accompanied by increasing 3H/3He ages, from 4.78 ± 0.44 years upgradient to more than 60 years downgradient. Discrepancies between calculated 3H/3He and 14C water ages (the latter ranging from 280 ± 56 to 17,050 ± 3410 years) suggest mixing between modern water and paleo-groundwater infiltrated through subglacial recharge when the Laurentide Ice Sheet covered the study area, and during the following deglaciation period. A linear relationship between 3H activity and corrected 14C versus Mg/Ca and Ba support a direct link between water residence time and the chemical evolution of these waters. The Ba, F, Fe, and Mn concentrations in groundwater originate from Paleozoic rocks from both the St. Lawrence Platform and the Appalachian Mountains. These elements have been brought to the surface by rising hydrothermal fluids along regional faults, and trapped in sediment during their deposition and diagenesis due to reactions with highly sulfurous and organic matter-rich water. Large-scale flow of meltwater during subglacial recharge and during the subsequent retreat of the Laurentide Ice Sheet might have contributed to the leaching of these deposits and their enrichment in the present aquifers. This study brings a new and original understanding of the St. Lawrence Lowlands groundwater system within the context of its geological evolution. Text Ice Sheet UQAM - Université du Québec à Montréal: archipel Canada Lawrence River ENVELOPE(-115.002,-115.002,58.384,58.384) Applied Geochemistry 65 1 13 |
institution |
Open Polar |
collection |
UQAM - Université du Québec à Montréal: archipel |
op_collection_id |
ftunivquebec |
language |
English |
topic |
Groundwater quality Groundwater residence times Regional geology St. Lawrence Lowlands Quebec (Canada) |
spellingShingle |
Groundwater quality Groundwater residence times Regional geology St. Lawrence Lowlands Quebec (Canada) Saby, Marion Larocque, Marie Pinti, Daniele L. Barbecot, Florent Sano, Yuji Castro, Maria Clara Linking groundwater quality to residence times and regional geology in the St. Lawrence Lowlands, southern Quebec, Canada |
topic_facet |
Groundwater quality Groundwater residence times Regional geology St. Lawrence Lowlands Quebec (Canada) |
description |
The assessment of groundwater quality in shallow aquifers is of high societal relevance given that large populations depend directly on these water resources. The purpose of this study was to establish links between groundwater quality, groundwater residence times, and regional geology in the St. Lawrence Lowlands fractured bedrock aquifer. The study focuses on a 4500 km2 watershed located in the St. Lawrence Lowlands of the province of Quebec in eastern Canada. A total of 150 wells were sampled for major, minor, and trace ions. Tritium (3H) and its daughter element, 3He, as well as radiocarbon activity (A14C) were measured in a subset of wells to estimate groundwater residence times. Results show that groundwater evolves from a Ca–HCO3 water type in recharge zones (i.e., the Appalachian piedmont) to a Na–HCO3 water type downgradient, toward the St. Lawrence River. Locally, barium (Ba), fluoride (F), iron (Fe), and manganese (Mn) concentrations reach 90, 2, 18, and 5.9 mg/L respectively, all exceeding their respective Canadian drinking water limits of 1, 1.5, 0.3, and 0.05 mg/L. Release of these elements into groundwater is mainly controlled by the groundwater redox state and pH conditions, as well as by the geology and the duration of rock–water interactions. This evolution is accompanied by increasing 3H/3He ages, from 4.78 ± 0.44 years upgradient to more than 60 years downgradient. Discrepancies between calculated 3H/3He and 14C water ages (the latter ranging from 280 ± 56 to 17,050 ± 3410 years) suggest mixing between modern water and paleo-groundwater infiltrated through subglacial recharge when the Laurentide Ice Sheet covered the study area, and during the following deglaciation period. A linear relationship between 3H activity and corrected 14C versus Mg/Ca and Ba support a direct link between water residence time and the chemical evolution of these waters. The Ba, F, Fe, and Mn concentrations in groundwater originate from Paleozoic rocks from both the St. Lawrence Platform and the Appalachian Mountains. These elements have been brought to the surface by rising hydrothermal fluids along regional faults, and trapped in sediment during their deposition and diagenesis due to reactions with highly sulfurous and organic matter-rich water. Large-scale flow of meltwater during subglacial recharge and during the subsequent retreat of the Laurentide Ice Sheet might have contributed to the leaching of these deposits and their enrichment in the present aquifers. This study brings a new and original understanding of the St. Lawrence Lowlands groundwater system within the context of its geological evolution. |
format |
Text |
author |
Saby, Marion Larocque, Marie Pinti, Daniele L. Barbecot, Florent Sano, Yuji Castro, Maria Clara |
author_facet |
Saby, Marion Larocque, Marie Pinti, Daniele L. Barbecot, Florent Sano, Yuji Castro, Maria Clara |
author_sort |
Saby, Marion |
title |
Linking groundwater quality to residence times and regional geology in the St. Lawrence Lowlands, southern Quebec, Canada |
title_short |
Linking groundwater quality to residence times and regional geology in the St. Lawrence Lowlands, southern Quebec, Canada |
title_full |
Linking groundwater quality to residence times and regional geology in the St. Lawrence Lowlands, southern Quebec, Canada |
title_fullStr |
Linking groundwater quality to residence times and regional geology in the St. Lawrence Lowlands, southern Quebec, Canada |
title_full_unstemmed |
Linking groundwater quality to residence times and regional geology in the St. Lawrence Lowlands, southern Quebec, Canada |
title_sort |
linking groundwater quality to residence times and regional geology in the st. lawrence lowlands, southern quebec, canada |
publishDate |
2016 |
url |
http://archipel.uqam.ca/8010/1/Saby%20et%20al%20%282015%29%20Applied%20Geochemistry.pdf |
long_lat |
ENVELOPE(-115.002,-115.002,58.384,58.384) |
geographic |
Canada Lawrence River |
geographic_facet |
Canada Lawrence River |
genre |
Ice Sheet |
genre_facet |
Ice Sheet |
op_relation |
http://archipel.uqam.ca/8010/ http://dx.doi.org/10.1016/j.apgeochem.2015.10.011 doi:10.1016/j.apgeochem.2015.10.011 |
op_doi |
https://doi.org/10.1016/j.apgeochem.2015.10.011 |
container_title |
Applied Geochemistry |
container_volume |
65 |
container_start_page |
1 |
op_container_end_page |
13 |
_version_ |
1766031467979210752 |