| Titre | Quantifying historical releases and pre-operation levels of metals and radionuclides |
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| Auteur | Sauvé, D; Clulow, V; Goulet, R R |
| Source | Journal of Environmental Radioactivity vol. 237, 106683, 2021 p. 1-15, https://doi.org/10.1016/j.jenvrad.2021.106683  Accès ouvert |
| Image |  |
| Année | 2021 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20210367 |
| Éditeur | Elsevier Ltd |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1016/j.jenvrad.2021.106683 |
| Media | papier; en ligne; numérique |
| Formats | pdf; html |
| Province | Ontario |
| Région | Elliot Lake |
| Lat/Long OENS | -83.6156 -82.1892 46.8150 45.9250 |
| Sujets | zinc; cuivre; plomb; nickel; uranium; Eau; minéraux radioactifs; Sciences et technologie; minéralogie |
| Illustrations | cartes de localisation; représentations graphiques combinées; tableaux; diagrammes |
| Diffusé | 2021 07 23 |
| Résumé | (disponible en anglais seulement)
Assessing the recovery of aquatic ecosystems from metal and radionuclide contamination requires knowledge of the concentration of radionuclides and metals
before anthropogenic releases. Pre-operational conditions, or baseline, are often unknown for many mining operations initiated decades ago. The objectives of this study were to quantify baseline levels of metals and radionuclides and describe
historical releases of an industrialised watershed in Northern Ontario where mining operations were carried out from 1955 to 1996. For this purpose, water and surface sediment samples were collected from this watershed and in an adjacent
non-industrialised watershed every 2 km. Using metal and radionuclide concentrations in the non-impacted watershed, we calculated water and sediment baseline concentrations as upper 95th percentile values. Baseline pH, 226Ra and uranium in water of
lakes and rivers were similar at pH of 6.8, 10 mBq·l-1, and 2.5 µg·l-1, respectively. For sediments, baseline lake sediment exhibited concentrations of radionuclides that were higher than river sediments. We calculated baseline concentrations in lake
sediment at 2,115 Bq·kg-1 210Pb, 535 Bq·kg-1 210Po, 218 Bq·kg-1 226Ra, 235 Bq· kg-1 228Th, 184 Bq·kg-1 230Th, and 223 Bq·kg-1 232Th. Baseline concentrations of metal levels in lakes were at 98 mg kg-1 Ni, 119 mg kg-1 Cu, 2300 mg kg-1 Zn, 112 mg kg-1
Pb and 19 mg kg-1 U. In Lake Huron, we collected two sediment core profiles along with surface sediment to estimate baseline radionuclide activities and metal concentrations and quantify historical releases from the industrialised watershed. The
sediment core profiles reflected baseline conditions prior to releases from the uranium mining operation and contamination from its onset in 1955 to its closure in 1996. Concentration of metals in pre-industrial sediment layers were lower than in
surface sediment of Lake Huron, suggesting atmospheric depositions. Our study indicates that collecting surface sediment in this non-impacted watershed may yield baseline concentrations for uranium and radionuclides. For metal, collecting surface
sediment may yield ambient metal concentrations because of long-range atmospheric transport from remote sources. By comparison, sedimentary profiles can provide baseline concentrations of both metals and radionuclides. In the case of the Serpent
River watershed, we report that water quality has recovered downstream of Quirke Lake as of 1993 and that additional sediment cores would better assess sediment recovery. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Évaluer si un écosystème aquatique est rétabli d'une exposition aux métaux et radionucléide nécessite de connaitre les teneurs ambiantes avant
le début des opérations minières. Malheureusement, cette information n'est pas toujours disponible. Nous avons donc pris des échantillons d'eau et de sédiment dans un bassin versant non-affecté et obtenu des valeurs ambiantes dans les eaux de surface
et les sédiments. Les concentrations ambiantes étaient plus élevées dans les lacs que les rivières. Dans le Lac Huron, nous avons prélevé deux carottes de sédiment qui ont permis de mesurer les valeurs ambiantes en métaux et radionucléide avant les
activités minières de la région d'Elliott Lake. Nos données indiquent que la qualité de l'eau en aval du Lac Quirke en 1993 est semblable aux valeurs ambiantes alors qu'il faudrait prendre des carottes de sédiment afin de confirmer que les
concentrations en métaux et sédiment sont de nos jours similaires aux valeurs ambiantes d'avant les opération minières. |
| GEOSCAN ID | 329118 |
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