Asynchronous Reductive Release of Iron and Organic Carbon from Hematite-Humic Acid Complexes
Bibliographic record
Abstract
Abstract Solid-phase iron (Fe) plays an important role in the accumulation and stabilization of soil organic matter (SOM). However, ferric minerals are subject to redox reactions, which can compromise the stability of Fe-bound SOM. To date, there is limited information available concerning the fate of Fe-bound SOM during redox reactions at Fe mineral surfaces. In this study, we investigated the release kinetics of hematite-bound organic carbon (OC) during the abiotic reduction of hematite–humic acid (HA) complexes by dithionite, to elucidate important processes governing the stability and fate of organic matter during the redox processes. Our results indicate that the reductive release of Fe obeyed first-order kinetics with release rate constants of 6.67–13.0 × 10− 3 min− 1. The Fe-bound OC was released rapidly during the initial stage with release rate constants of 0.011–1.49 min− 1, and then became stable with residual fractions of 4.6–58.2% between 120 and 240 min. The release rate of aromatic OC was much faster than for the non-aromatic fraction of HA, and 90% of aromatic OC was released within the first hour for most samples. Our findings show that in the reductive reaction the mobilization of Fe-bound OC was asynchronous with the reduction of Fe, and aromatic OC was released more readily than other components of SOM. This study highlights the importance of evaluating the release of SOM bound with Fe during the redox reactions, especially the influence of the physicochemical properties of SOM.
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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".