Insights into the biogenic contribution to total sulphate in aerosol and precipitation in the Fraser Valley afforded by isotopes of sulphur and oxygen
Bibliographic record
Abstract
Contributions to atmospheric sulphate aerosol and precipitation in the Fraser Valley and at Saturna Island, Canada, from oxidation of biogenic dimethyl sulphide were determined using an isotopic mass balance approach. The S‐isotope composition of aerosol sulphate, and sulphur dioxide from a variety of industrial sources in the region were investigated and were found to have δ34S values ranging between −1.6 and +9‰. Isotopic analysis suggests a U.S. oil refinery and/or H2S from tidal flats on the coast contributes to the aerosol sulphate load in both summer and winter. On average, well‐mixed air in the region had δ34S values for SO2 near +1‰. Assuming this represents the average isotope composition of multiple sulphate sources from urban pollution, refinery emissions, and H2S, the DMS contributions to sulphate aerosol were calculated. On average, biogenic DMS‐sulphate made up 30% of the non‐sea salt sulphate in precipitation at Saturna Island in the Strait of Georgia. In contrast, it comprised only 13% of the aerosol sulphate load in the Fraser Valley. Proportionately more DMS aerosol sulphate is observed at Powell River and on Vancouver Island than in the vicinity of the city of Vancouver. Estimated concentrations are highest in the north, reaching 1.4 μgS/m3. These results are consistent with the isotope composition of oxygen in sulphate which show that at least half the aerosol sulphate in the Fraser Valley is formed from oxidation of SO2 at ambient temperatures.
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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 | 0.000 | 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) | 0.000 | 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 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".