Observations of peroxycarboxylic nitric anhydrides and intermediate volatility organic compounds in the Alberta oil sands in winter
Bibliographic record
Abstract
The photolysis branching ratio of methyl ethyl ketone (MEK) was re-evaluated using light emitting diodes centered at 285 nm or 315 nm (demonstrates atmospheric relevance) to irradiate MEK in the presence of nitric oxide (NO) and oxygen (O2). This produced peroxyacetic nitric anhydride (PAN) and peroxypropanoic nitric anhydride (PPN), which were then quantitated by gas chromatography electron capture detection (GC-ECD). The MEK photolysis branching ratio at 285 nm was determined as α = (7±1)% + (1.1±0.7)*10^(-4)*(T-298) for 250 K < T < 300 K (±2σ). The experiment described provides a more accurate and precise MEK branching ratio due to their lower concentration which minimizes secondary chemistry effects. Measurements of peroxycarboxylic nitric anhydrides and intermediate volatile organic compounds (IVOCs) were conducted at the Oski-Ôtin field site north of Fort McKay, Alberta (AB), Canada during the SNOWDOGS field campaign. A calibrated GC-ECD was used to quantitate PAN and PPN and semi-quantitate peroxyacrylic nitric anhydride (APAN). Photochemical day-time production of PAN and PPN was observed up to 28.8±4.6 ppt and 4.6±1.9 ppt (1σ), respectively. Minor photochemical production of APAN suggests that PAN emissions were associated to petrochemical activities. Surface deposition of PAN and PPN onto snow/ice was proposed as an alternative sink in winter with estimated deposition velocities of up to 1 cm/s. The PPN:PAN ratio was found to be 23% indicating the majority of PAN originated from anthropogenic sources. Ambient IVOCs were measured by gas chromatography ion trap mass spectrometry and combined with primary emission and meteorological data. Principal component analysis was conducted to reduce the dimensionality of the dataset followed by application of the Gaussian mixture model (GMM) clustering algorithm to isolate local IVOC sources. Chemical signatures were consistent with single ring aromatics; previously assumed to constitute a small portion of IVOCs in the region during summertime studies.
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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 | 0.000 |
| Science and technology studies | 0.001 | 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".