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Signature isotopique du plomb pour le marquage de la contamination des sols à proximité d'une fonderie de métaux, nord-ouest du Québec, Canada.

Hou, Xiaohong (2004). Signature isotopique du plomb pour le marquage de la contamination des sols à proximité d'une fonderie de métaux, nord-ouest du Québec, Canada. Mémoire. Québec, Université du Québec, Institut national de la recherche scientifique, Maîtrise en sciences de la terre, 100 p.

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The Rouyn-Noranda region is one in which numerous mining and smelting activities have taken place since the opening of the Home mine in 1922 and the construction of the Home smelter in December 1927. Before the program "Rouyn-Noranda Ville En Santé" was launched in 1987, the mining and smelting community had earned a reputation as the most polluted city in Canada because of serious environmental problems such as sulfur dioxide plumes, heavy metal fallout as well as acid rain. This project is part of the Metals in the environment (MITE) program of the Geological Survey of Canada. The major objectives of this project are: 1) to determine the extent of Pb contamination of soils exposed to Home smelter emissions; 2) to distinguish the source of anthropogenic lead in soils using stable Pb isotope ratios; and 3) to estimate the downward migration of Pb in representative mesic soils. Seventy five (75) samples were collected from podzolic soil profiles at eight (8) sites, six (6) of which lie along a northeast-southwest transect crossing Rouyn-Noranda, northwestem Quebec, while the other two (2) are from Grande Rivière de la Baleine region, approximately 800 km north of Rouyn-Noranda. Pb concentrations and Pb isotopic compositions were determined on the fine-grained fraction of soil samples leached by three extraction methods ofincreasing agressivity: (1) Mehlich-III, (2) 0.25 M HCI, and (3) total digestion by an acid mixture of HF, HN03, HCI, and HCI04. Pb is enriched in the surface organic horizons at all sites in Rouyn-Noranda. Its concentration decreases by two orders of magnitude from the surface organic horizons to the underlying mineraI horizons. Pb isotope ratios are low in surface organic horizons, and they increase sharply in the mineraI horizons. Along the NE-SW transect, average Pb concentration is as high as 869 ppm in organic horizons at site 1, c1osest to the smelter. It decreases exponentially with increasing distance from the smelter, reaching a value of 39 ppm at site 10, 116 km northeast of the Home smelter. The lowest average 206Pb/207Pb ratio (0.99) is observed at site 1 and the highest ratio (1.15) is found at site 10. At site 1, the highest Pb concentration of 1414 ppm is also accompanied by the lowest 206Pb/207Pb ratio (0.98), which is close to the isotopie composition of Noranda galena (206Pb/207Pb = 0.92). Both Pb concentrations and isotopie compositions indicate that the Horne smelter is the main source of Pb contamination of soils in the Rouyn-Noranda region. Canadian anthropogenic emissions are also known to contribute modestly to the overall lead levels in soils of the Rouyn-Noranda region, but this contribution cannot be established quantitatively. Two soil profiles from Grande-Baleine display different trend of Pb concentration and isotope ratios with depth. Based on Pb concentration and isotopie composition in the Rouyn-Noranda soil profiles, it is estimated that anthropogenic lead has migrated downward to a depth of ~ 1 0-30 cm, which yields a mobility of ~ 1-4 mm/a.

Type de document: Mémoire
Directeur de mémoire/thèse: Parent, Michel
Co-directeurs de mémoire/thèse: Savard, Martine M.; Tassé, Normand
Informations complémentaires: Résumé avec symboles
Mots-clés libres: plomb; contamination; sols; fonderie; métaux; isotope; Québec
Centre: Centre Eau Terre Environnement
Date de dépôt: 21 nov. 2012 19:54
Dernière modification: 20 nov. 2015 16:40
URI: http://espace.inrs.ca/id/eprint/382

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