Temporal and spatial variability of halogenated compounds and other trace gases
Bibliographic record
Abstract
Air samples. from four aircraft campaigns and two surface experiments covering a large geographical area over both hemispheres have been analysed using the technique of gas chromatography mass spectroscopy (GCMS). Around 40 trace gases have been detected and where possible quantified, including most of the CFC's, HCFC's, and halon's, HFC-134a, HFC-152a, HFC-365mfc, CCI4, CH3CCb, CH3Br, CH3CI, and a number of short lived halogenated compounds including CH31, CHBr3, CH2BrCI, and n-C3H7Br. From the data obtained it has been possible to investigate the spatial and temporal variability of halogenated compounds, including variations with altitude, longitude, and interhemispheric ratios. Significant quantities of the short lived bromocarbons (CHBr3, CH2Br2, CH2BrCI, CHBr2CI, CHBrCI2, n-C3H7Br) and methyl iodide (CH31) have been observed in air samples collected within the upper troposphere lower stratosphere (UTLS) region of the atmosphere, implying that the contribution of these compounds to stratospheric ozone loss is potentially significant. Evidence has also been found which suggests that sub-tropical regions of the Pacific Ocean and' coastal waters around the Phillipines are particularly productive source regions for all of these compounds. In addition using data from a plant enclosure study the potential for terrestrial ecosystems to both emit and take up a number of halogenated compounds has been identified. Although the significance of these results remains unclear. The atmospheric mixing ratios of all four CFCs measured in this study are decreasing due to the reduction in global emissions of these compounds as a result of their regulation under the Montreal Protocol. A significant decrease in the mixing ratios of carbon tetrachloride (CCI4) and methyl chloroform (CH3CCb) has also been observed in the 2000 - 2006 CARIBIC data. In contrast there is evidence to suggest that halon's 1211 and 2402 are still slowly increasing in the atmosphere. For all the HCFC's and HFC's measured in this study (HCFC-21, HCFC22, HCFC-141b, HCFC-142b, HCFC-124, HCFC-123, HFC-134a, HFC-152a, and HFC365mfc), clear inter hemispheric gradients were observed with higher mixing ratios in the NH, consistent with a predominantly NH anthropogenic source for these compounds. However there is evidence to suggest that emissions from Asia are becoming increasingly important for a number of these compounds. In addition evidence was found which suggests a continuing source for CFC-11, CFC-12, CFC-113 and CFC-114.
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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 | 0.001 | 0.001 |
| 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) | 0.001 | 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".