Methyl bromide loss rates in surface waters of the North Atlantic Ocean, Caribbean Sea, and eastern Pacific Ocean (8°–45°N)
Bibliographic record
Abstract
The first‐order loss rate constant of methyl bromide was measured in surface seawater samples from the North Atlantic Ocean, Caribbean Sea, and coastal eastern Pacific Ocean during May‐July 1998. A stable isotope incubation technique was used, which consisted of spiking seawater samples with 13CH3Br and following the loss rate of the isotopically labeled spike with gas chromatography and isotope dilution mass spectrometry. The analysis of both filtered and unfiltered aliquots of seawater provides insight into the relative importance of chemical and particle‐related (presumably biological) degradation pathways. Over the entire cruise, first‐order total degradation rate constants ranged from 0.03–0.40 day−1. On average, higher rate constants were observed during the last part of the cruise in the Caribbean Sea (mean 0.34 day−1) and coastal Pacific waters (0.31 day−1), than in the earlier passage through the North Atlantic Ocean (0.18 day−1, legs 1 and 3). In the warm waters of the Caribbean Sea and the Pacific, total degradation rate constants were controlled primarily by chemical losses (0.30 and 0.25 day−1, respectively). In the colder Atlantic waters the average chemical loss rate constant was lower (0.11 day−1), and biological losses constituted a significant fraction of the total loss rate constant (35%). Chemical loss rate constants varied strongly with water temperature, in good agreement with previous determinations of the rate constant for methyl bromide removal from seawater due to chloride substitution and hydrolysis. Biological losses were detected in most of the water samples analyzed, suggesting that the biological capability to degrade methyl bromide is ubiquitous in the oceans. Rate constants for biological removal exhibited no apparent relationship to seawater temperature, salinity, chlorophyll, or bacterial counts.
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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 | 0.001 |
| 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) | 0.000 | 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".