Biogeochemical prospecting for buried uranium mineralization and the investigation of black spruce trees as a tool for biogeochemical sampling and for environmental monitoring of radionuclide contamination
Notice bibliographique
Résumé
Surface geochemical methods were applied to delineate uranium (U) \nmineralization buried under till cover in the Jacque’s Lake area, Labrador. Samples \nanalyzed included black spruce twigs, bark, and needles; Labrador tea leaves and stems, \nand B-horizon soil. These results were compared to defined radiometric U/Th anomalies \nin the study area. Relative U enrichment followed the order: spruce twigs>bark \n>Labrador tea stem>spruce needles>Labrador tea leaves. Spruce twigs displayed the \ngreatest contrasts in U contents and exhibited a significant association with the U/Th \nanomalies. Twig U concentrations ranged between <0.01 to 61 ppm and were highly \ncorrelated with Pb, Ag, Sb, Ca, and Be. Areas with anomalous U concentration in <250 \nμm sized-fraction of B-horizon soil appeared displaced east of the defined U/Th \nresponses and the near surface projection of the buried U mineralization. There is a lack \nof correlation between U concentration in B-horizon soil and the defined radiometric \nanomalies. \nThe U hyperaccumulation by black spruce trees was investigated and the possible \nuse of ²³⁸U/²³⁵U ratio as a tracer for fingerprinting the source and transport pathways of U \ntaken up by vegetation was examined. The U accumulation property of the black spruce \nseedlings was evaluated by measuring the metal uptake in seedlings grown in peat and in \nsoil treated with varying concentrations of uranyl nitrate. The bioavailability indexes of U \nin soil treated with 100, 250, and 400 mg U/Kg soil were estimated to be 0.21, 0.15 and \n0.10 respectively. Uranium concentrations in seedling stems, the Biological \nAccumulation Coefficient (BAC), and Transfer Factors (TF) increased linearly with increasing bioavailable concentration of U in the substrates. The metal accumulation in \nthe plant tissues followed the order stem > roots > needles. Although the trend of U \naccumulation was comparable for plants grown in U-dosed soil versus U-dosed peat, the \nBAC values for plants grown in U-spiked soils were higher suggesting that metal \navailability was substrate specific. \nThe source of U taken up by the spruce seedlings was evaluated by Inductively \nCoupled Plasma-Quadrupole Mass Spectrometry (ICP-QMS) and Neutron Activation \nAnalysis (NAA) analyses of ²³⁸U/²³⁵U ratios in stems of seedlings grown on substrates \nmounted in solutions spiked with different concentrations of DU. The ²³⁸U/²³⁵U ratio in \nthe stems exhibited measureable deviations from the natural ratio (137.88) and ranged \nfrom 174-210 and is a consequence of the bulk uptake of U derived from the DU \nsolutions. Elevated ²³⁸U/²³⁵U ratio in the substrates suggests upward migration of DUenriched \nsolution along the substrate column. The precision (1σ) for ICP-QMS \ndetermination of ²³⁸U/²³⁵U in DU-spiked substrates, and the stems of seedlings, are \n0.02%-2.7% and 0.05%-1.9%, respectively.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,002 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,001 | 0,000 |
| Études des sciences et des technologies | 0,002 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,001 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».