Medusa-Aqua system: simultaneous measurement and evaluation of novel potential halogenated transient tracers HCFCs, HFCs and PFCs in the ocean
Bibliographic record
Abstract
Abstract. This study evaluates the potential usefulness of the halogenated compounds HCFC-22, HCFC-141b, HCFC-142b, HFC-134a, HFC-125, HFC-23, PFC-14 and PFC-116 as the time-dependent oceanographic transient tracers in order to better constrain ocean ventilation processes. We collected seawater samples and improved on an established analytical technique, the Medusa-Aqua system, to simultaneous measure them, and estimate their stability in seawater following previous work on the atmospheric history and solubility. HCFC-22, HCFC-141b, HCFC-142b, HFC-134a and HFC-125 have been measured in profiles in the Mediterranean Sea for the first time. We estimated the historic surface saturation anomalies of transient tracers in the Mediterranean Sea by evaluating the historic record. Their stability in seawater was estimated by analysis of their ocean partial lifetimes, seawater surface saturations and concentrations compared to CFC-12 measurements by a well-established technique. Of the investigated compounds, HCFC-141b was found to be the most promising transient tracer in the ocean; it fulfills several essential requirements by virtue of well-documented atmospheric history, established seawater solubility, inertness in seawater and feasible measurements and indication of conservative behavior in seawater by having mean ages in agreement to be expected from both CFC-12 and SF6 observations. However, more information on degradation is needed to further identify its stability in seawater, and HCFC-141b has restrictions on production and consumption imposed by the Montreal Protocol leading to its decreasing atmospheric mole fractions since 2017. The most potential oceanic transient tracers were PFC-14 and PFC-116 due to their stability in seawater, the long and well-documented atmospheric concentrations histories and constructed seawater solubility functions, although the low solubility in seawater creates challenging measurement conditions (i.e. low concentration). Measurements of PFCs can be potentially improved by modifying the Medusa-Aqua analytical system. With the exception of providing the information on the novel potential alternative oceanic transient tracers, this study also provides a method on how to evaluate the feasibility for a compound to be a transient tracer in the ocean.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".