Iron‐Mediated Organic Matter Preservation in the Mississippi River‐Influenced Shelf Sediments
Bibliographic record
Abstract
Abstract Continental shelves are important land–ocean interfaces where natural and anthropogenic processes as well as sediment geochemistry regulate organic matter sequestration. The major objective of this work is to understand spatial variability in reactive iron (rFe) bound organic carbon (OC) during low‐ and high‐flow conditions in the recent sediments of the Mississippi River‐influenced Louisiana shelf in the Northern Gulf of Mexico. Sediment samples were collected from five sites along the river plume during low (August 2016) and high (May 2017) discharge. Reactive iron was significantly higher in May (6.9 ± 1.7 mg g −1 dw ) compared to August (4.3 ± 0.9 mg g −1 dw ), while OC in August (11.9 ± 3.7 mg g −1 dw ) and May (7.8 ± 4.8 mg g −1 dw ) was similar. The fraction of OC bound to rFe (Fe‐OC) in the sediment in May (2.4 ± 1.5 mg g −1 dw ) was not significantly different from August (3.7 ± 2.7 mg g −1 dw ). Molar OC:Fe ratios in the rFe‐associated OC ranged between 0.9 and 6.2, with higher ratios in the deeper sediments (6–20 cm). Our results show that 31.7% ± 6.2% of the total OC in the recent sediments is associated with the rFe phase. Sediment mineralogical composition was characterized using X‐ray diffractometry and Fe‐K edge X‐ray absorption near edge structure spectroscopy. Our findings indicate that most of the iron is present as nonreactive iron in clay mineral smectite and the dominant form of rFe associated with OC is goethite.
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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 | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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".