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
Bibliographic record
Abstract
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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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".