Incomplete sulfide oxidation under sub-oxic conditions: Rates and aqueous sulfur speciation
Bibliographic record
Abstract
The oxidative dissolution of sulfide minerals consumes oxygen and can generate redox gradients in mine wastes that affect the mobility of redox-sensitive solutes. However, the controls of oxygen depletion on sulfide reactivity and sulfur mobilization remain poorly constrained, complicating the long-term assessment of drainage quality dynamics. We investigated pyrite and Fe-rich sphalerite weathering using aqueous S speciation and quantitative mineralogical analyses under controlled, ambient versus sub-oxic, conditions at 6 < pH < 9. Titration assays revealed that oxidation rates for pyrite (up to 10−10 mol m−2 s−1) were higher than for sphalerite (up to 10−11 mol m−2 s−1) and, for both minerals, decreased by two orders-of-magnitude under sub-oxic (<50 ppm O2) conditions. Precipitation of secondary S-bearing minerals was restricted to elemental S, with no sulfate- or thiosulfate-salts detectable >0.01 wt%. Sulfate was the dominant aqueous S species produced in all experiments, but significant amounts of thiosulfate, tetrathionate, and sulfite were also found. These dissolved intermediate S species were abundant under both sub-oxic and oxic conditions, and broadly in line with known sulfide oxidation mechanisms, even though the weathering of pyrite produced several factors less incompletely oxidized S than that of sphalerite, under otherwise comparable conditions. This work shows that a range of intermediate S species may be produced even in low-reactivity conditions and may help optimize the management of such mine waste materials.
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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 | 0.000 | 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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".