ABIOTIC AND BIOTIC SEQUESTRATION OF SELENIUM IN ANOXIC COAL WASTE ROCK
Bibliographic record
Abstract
Waste rock dumps at coal mines in the Elk Valley are the primary source of selenium (Se) in the Elk River.The mobile Se oxyanions, Se(IV) and Se(VI), can be adsorbed to mineral phases or reduced biotically or abiotically to Se solid phases, such as Se(0).Microbial analyses and geochemical testing were conducted to determine if Se can be sequestered in anoxic coal waste rock by these mechanisms.Testing was conducted on a waste rock sample collected from the West Line Creek waste rock dump in the Elk Valley and a water sample collected from the rock drain flowing beneath the dump.Microbial analyses included culturing with plate and broth media and 16S rRNA gene sequencing.The key finding from these analyses was that bacteria capable of reducing Se(VI) to Se(0) were present in the waste rock sample and bacteria capable of reducing Se(IV) to Se(0) were present in the rock drain water sample.Geochemical tests included abiotic batch tests on waste rock and pure minerals, non-sterile batch tests on waste rock, and desorption batch tests on waste rock, as well as several solids analysis techniques, such as X-ray Absorption Spectroscopy and Energy Dispersive X-ray Spectroscopy.Batch tests were conducted at circumneutral pH in an anoxic glove box to simulate an anoxic zone of a waste rock dump.Batch testing on pure minerals present in the waste rock sample determined that siderite can reduce Se(VI) to Se(IV) and that siderite, pyrite, and sphalerite can adsorb Se(IV) and reduce Se(IV) to Se(0).Under sterile conditions, waste rock did not reduce Se(VI) but it did adsorb Se(IV) and reduce Se(IV) to Se(0).Under non-sterile conditions, Se(VI) was reduced to Se(IV) much faster than the sterile tests with siderite and Se(IV) was removed from solution by a combination of adsorption, biotic reduction, and abiotic reduction.Desorption batch testing showed that a fraction of sequestered Se was susceptible to desorption but that the fraction decreased over time.These findings suggest that sequestration of Se in anoxic coal waste rock is a viable method to decrease the amount of Se discharging from Elk Valley waste rock dumps.iii
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".