Lead and Cadmium Interactions with Mackinawite: Retention Mechanisms and the Role of pH
Bibliographic record
Abstract
The reactive iron monosulfides including mackinawite are known for their ability to scavenge trace metals. Oxidation and reduction reactions in sediments and the types of metal bonding with mackinawite determine both the stability of the metal bonds and the susceptibility of the material to oxidation. Metal retention is important because it influences the availability of toxic metals to aquatic organisms. In this study, Pb and Cd interactions with mackinawite were investigated, and two major retention mechanisms were suggested. They are, first, that Pb and Cd displace up to 29% of the Fe from mackinawite by forming (Pb,Fe)S and (Cd,Fe)S on the surface of the mackinawite and, second, that 0.91 mmol/g of Pb and 2.03 mmol/g of Cd are adsorbed on the surface of the transformed mackinawite. The mixed ferrous sulfides are more insoluble and more stable than the pure mackinawite, while surface adsorption is a relatively weak and labile retention mechanism. Both reactions contributed toward a drop in pH, although the mackinawite containing Pb and Cd was stable at this lower pH.
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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 | 0.001 | 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 | 0.010 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".