Stable sulfur isotope measurements to trace the fate of SO <sub>2</sub> in the Athabasca oil sands region
Bibliographic record
Abstract
Concentrations and δ 34 S values for SO 2 and size-segregated sulfate aerosols were determined for air monitoring station 13 (AMS 13) at Fort MacKay in the Athabasca oil sands region, northeastern Alberta, Canada as part of the Joint Canada-Alberta Implementation Plan for Oil Sands Monitoring (JOSM) campaign from 13 August to 5 September 2013. Sulfate aerosols and SO 2 were collected on filters using a high-volume sampler, with 12 or 24 h time intervals. Sulfur dioxide (SO 2 ) enriched in 34 S was exhausted by a chemical ionization mass spectrometer (CIMS) operated at the measurement site and affected isotope samples for a portion of the sampling period. It was realized that this could be a useful tracer and samples collected were divided into two sets. The first set includes periods when the CIMS was not running (CIMS-OFF) and no 34 SO 2 was emitted. The second set is for periods when the CIMS was running (CIMS-ON) and 34 SO 2 was expected to affect SO 2 and sulfate high-volume filter samples. δ 34 S values for sulfate aerosols with diameter D >0.49 µm during CIMS-OFF periods (no tracer 34 SO 2 present) indicate the sulfur isotope characteristics of secondary sulfate in the region. Such aerosols had δ 34 S values that were isotopically lighter (down to −5.3 ‰) than what was expected according to potential sulfur sources in the Athabasca oil sands region (+3.9 to +11.5 ‰). Lighter δ 34 S values for larger aerosol size fractions are contrary to expectations for primary unrefined sulfur from untreated oil sands (+6.4 ‰) mixed with secondary sulfate from SO 2 oxidation and accompanied by isotope fractionation in gas phase reactions with OH or the aqueous phase by H 2 O 2 or O 3 . Furthermore, analysis of 34 S enhancements of sulfate and SO 2 during CIMS-ON periods indicated rapid oxidation of SO 2 from this local source at ground level on the surface of aerosols before reaching the high-volume sampler or on the collected aerosols on the filters in the high-volume sampler. Anti-correlations between δ 34 S values of dominantly secondary sulfate aerosols with D < 0.49 µm and the concentrations of Fe and Mn ( r = −0.80 and r = −0.76, respectively) were observed, suggesting that SO 2 was oxidized by a transition metal ion (TMI) catalyzed pathway involving O 2 and Fe 3+ and/or Mn 2+ , an oxidation pathway known to favor lighter sulfur isotopes. Correlations between SO 2 to sulfate conversion ratio ( F ( s )) and the concentrations of α -pinene ( r = 0.85), β -pinene ( r = 0.87), and limonene ( r = 0.82) during daytime suggests that SO 2 oxidation by Criegee biradicals may be a potential oxidation pathway in the study region.
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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| 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".