The fate of CO2, Ca, and Mg after terrestrial rock weathering
Bibliographic record
Abstract
Abstract The silicate–carbonate cycle controls atmospheric CO2 concentrations and moderates Earth’s climate over geologic time scales. Chemical weathering of silicate minerals by CO2 results in the release of cations and the neutralization of CO2 to HCO3− or CO32−. The precipitation of Ca- and Mg-carbonate minerals is expected once waters are supersaturated. However, quantifying the magnitude of supersaturation required, particularly for Mg-carbonates, has remained challenging. Here we present a database of 854 water samples from the Central Plateau, British Columbia, Canada, representing a wide range of salinities, including both Na–(SO4)–HCO3–CO3 and Mg–Na–SO4 hypersaline lakes, to determine the geochemical thresholds for Ca- and Mg-carbonate formation. For HCO3-dominated waters, the data indicate maximum alkalinity thresholds of ~5 mEq/kg for Ca-carbonates and ~40 mEq/kg for Mg-carbonates. Activity plots of Ca–CO32− and Mg–CO32− suggest that maximum saturation thresholds for both Ca-carbonates and Mg-carbonates are applicable to HCO3-dominated, SO4-dominated, and CO2-rich waters. These geochemical thresholds may be used to optimize geochemical carbon dioxide removal (geoCDR) technologies, such as enhanced rock weathering, as HCO3− has up to double the CDR efficiency of carbonate minerals.
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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 | 0.000 |
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".