The oxidative weathering of organic matter and its carbon dioxide emissions: Insight from the trace elements rhenium and molybdenum
Bibliographic record
Abstract
Throughout geological history, the exposure of sedimentary rocks to chemical weathering at Earth’s surface has profoundly affected the geochemistry of the atmosphere, rivers and oceans. Oxidative weathering reactions can release redox-sensitive trace elements, and the concentration and isotope composition of these elements in geological materials may provide an insight into the environmental conditions and processes occurring both today and over Earth’s history. To constrain how Earth’s geological carbon cycle operates, and the influence it has on global climate change, a better understanding of the controls on oxidative weathering is required. The oxidation of organic carbon in sedimentary rocks (petrogenic organic carbon, OCpetro) releases carbon dioxide (CO2) from long-term storage in the lithosphere, and consumes atmospheric O2. Alongside volcanism, the oxidative weathering of OCpetro is the main source of CO2 to the atmosphere over millions of years. However, OCpetro oxidation is poorly understood, both in terms of the rate at which it releases CO2 and the factors that interact to drive the reaction. Trace metals associated with organic matter in rocks, such as rhenium (Re) and molybdenum (Mo), can be released to the dissolved load of rivers during oxidative weathering. Quantifying these element fluxes has the potential, therefore, to provide insight into the oxidative weathering processes involved. Here, rates of OCpetro oxidation rates are quantified in rapidly eroding mountain river catchments in the western Southern Alps, New Zealand, and the Mackenzie River Basin, north west Canada. Physical erosion is found to be a first order control on the oxidative weathering fluxes, but catchments dominated by valley glaciers and exposed to frost-shattering processes experience a further two to three times elevation in CO2 emissions relative to catchments with less glacial cover. The oxidative weathering processes are also found to fractionate metal isotopes (e.g. Mo) in the Critical Zone, which places an important control on the Mo isotope composition of both continental runoff and the World’s oceans.
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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 | 0.001 | 0.001 |
| 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".