Biomolecule-induced carbonate genesis in abiotic formation of humic substances in nature
Bibliographic record
Abstract
Most soil C sequestration research has focused on organic C stabilization, while carbonate precipitation has received little attention. Mineral colloids can accelerate abiotic humification reactions of biomolecules such as amino acids, sugars, and polyphenols, derived from the breakdown of biological residues and metabolites. During these reactions CO2 is produced as a result of the oxidation of biomolecules. However, the biomolecule-induced formation of carbonate during abiotic humification remained to be uncovered. Here we demonstrate using X-ray diffraction, Fourier transform infrared spectroscopy and C K-edge and Mn L-edge near edge X-ray absorption fine structure spectroscopy that the Maillard reaction (glucose and glycine) and the integrated polyphenol-Maillard reaction pathway (catechol, glucose and glycine), in the presence of birnessite (δ-MnO2) produce MnCO3 (rhodochrosite). Increasing the molar ratio of catechol to glucose and glycine dramatically hampered carbonate formation, which is attributed to the enhanced formation of humic polymers, which increased proton generation and perturbed rhodochrosite crystallization through Mn(II)-humic complexation in the reaction systems. Thus, rhodochrosite formation was a competing reaction with humic substance formation. Our findings are of fundamental significance in understanding the vital role of the nature and relative abundance of biomolecules in abiotic carbonate formation, which merits close attention in understanding and regulating C sequestration in natural environments.Key words: Abiotic humification, polyphenol-Maillard reaction, rhodochrosite, birnessite, C K-edge and Mn L-edge NEXAFS
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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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".