Uranium\nSpeciation\nand Mobilization in Thawing Permafrost
Bibliographic record
Abstract
Uranium is a toxic and pervasive geogenic contaminant often associated with organic matter. Its abundance and speciation in organic-rich permafrost soils are unknown, thereby limiting our ability to assess risks associated with uranium mobilization during permafrost thaw. In this study, we assessed uranium speciation in permafrost soil and porewater liberated during thaw using active-layer and permafrost samples from a study area in Yukon, Canada where elevated uranium concentrations occur in bedrock and groundwater. Permafrost contained 1.1–28 wt % organic carbon and elevated uranium (range 7.6–1040 μg g–1, median 25 μg g–1) relative to local bedrock. The highest soil uranium concentrations were encountered in catchments hosting uranium-enriched bedrock and correlated positively with soil organic carbon. X-ray absorption spectroscopy, micro-X-ray fluorescence, and electron microscopy analyses revealed that solid-phase uranium predominantly occurs as uranium(VI) associated with soil organic matter. Extended X-ray absorption fine structure (EXAFS) analyses suggested the presence of uranium(VI) coordinated with carbon, consistent with bidentate-mononuclear uranyl complexation on carboxyl groups. Permafrost thaw produced circumneutral pH porewater (pH 6.2–7.5) with elevated dissolved uranium (0.5–203 μg L–1). Geochemical modeling indicated that calcium-uranyl-carbonate complexes dominated the dissolved uranium speciation. This study highlights that permafrost soil can mobilize uranium upon thaw and that uranium fate is linked to dynamic biogeochemical reactions involving organic carbon and groundwater chemistry.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 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 source (direct Gemma or distilled Codex), 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".