Hydrogen Isotopic Composition of Arctic and Atmospheric CH <sub>4</sub> Determined by a Portable Near-Infrared Cavity Ring-Down Spectrometer with a Cryogenic Pre-Concentrator
Bibliographic record
Abstract
In this study, near-infrared continuous wave cavity ring-down spectroscopy was applied to the measurement of the δ 2 H of methane (CH 4 ). The cavity ring-down spectrometer (CRDS) system consisted of multiple DFB laser diodes to optimize selection of spectral line pairs. By rapidly switching measurements between spectral line peaks and the baseline regions, the long-term instrumental drift was minimized, substantially increasing measurement precision. The CRDS system coupled with a cryogenic pre-concentrator measured the δ 2 H of terrestrial atmospheric CH 4 from 3 standard liters of air with a precision of ±1.7‰. The rapidity with which both C and H isotopic measurements of CH 4 can be made with the CRDS will enable hourly monitoring of diurnal variations in terrestrial atmospheric CH 4 signatures that can be used to increase the resolution of global climate models for the CH 4 cycle. Although the current instrument is not capable of measuring the δ 2 H of 10 ppbv of martian CH 4 , current technology does exist that could make this feasible for future spaceflight missions. As biological and abiotic CH 4 sources have overlapping carbon isotope signatures, dual-element (C and H) analysis is key to reliable differentiation of these sources. Such an instrument package would therefore offer improved ability to determine whether or not the CH 4 recently detected in the martian atmosphere is biogenic in origin. Key Words: Arctic—Hydrogen isotopes—Atmospheric CH 4 —CRDS—Laser. Astrobiology 16, 787–797.
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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 | 0.000 | 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 | 0.001 |
| 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 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".