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Tritium–helium groundwater age used to constrain a groundwater flow model of a valley-fill aquifer contaminated with trichloroethylene (Quebec, Canada).

Murphy, Samantha; Ouellon, Thomas; Ballard, Jean-Marc; Lefebvre, René; Clark, Ian D. (2011). Tritium–helium groundwater age used to constrain a groundwater flow model of a valley-fill aquifer contaminated with trichloroethylene (Quebec, Canada). Hydrogeology Journal , vol. 19 , nº 1. p. 195-207. DOI: 10.1007/s10040-010-0662-5.

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Résumé

Tritium–helium groundwater dating was carried out in a trichloroethylene (TCE)-contaminated valley-fill aquifer system in Quebec, Canada, where a numerical groundwater flow model was developed. Forty seven discrete groundwater and dissolved gas samples were obtained along two flow paths originating from known TCE source zones whose related plumes converge down gradient to form a single plume. Sampling points in monitoring wells were projected onto vertical sections showing particle tracks along the two flow paths. At these points, simulated advective ages obtained from particle tracking were matched to tritium–helium ages using different porosity values; the best match was 0.35. Ages were also obtained above and below a prodeltaic silty aquitard in a portion of the aquifer where some source zones are located, which provide groundwater and TCE transit times through the aquitard as well as a mean vertical hydraulic conductivity that agrees with previous estimates used in the model. In certain locations, anomalously old ages associated with high terrigenic 4He indicate areas where groundwater from the underlying proglacial unit flows upward into the deltaic sand aquifer through aquitard windows. Upflow locations correspond with increased TCE concentrations, suggesting significant TCE provenance through the proglacial unit originating from a previously unrecognized TCE source zone.

Type de document: Article
Mots-clés libres: tritium–helium groundwater dating; numerical modeling; model validation; groundwater transit time; Canada
Centre: Centre Eau Terre Environnement
Date de dépôt: 08 janv. 2021 14:36
Dernière modification: 08 janv. 2021 14:36
URI: http://espace.inrs.ca/id/eprint/10620

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