The accumulation and reactivity of polycyclic aromatic hydrocarbons on wildfire-influenced environmental surfaces
Bibliographic record
Abstract
Wildfires emit large amounts of pollutants into the atmosphere, including polycyclic aromatic hydrocarbons (PAHs). In my thesis, I investigate the accumulation and persistence of wildfire PAHs on two surfaces, urban grime and wildfire ash, and discuss the potential implications of their presence on the environment. In the first part, I investigate the potential accumulation of PAHs in wildfire smoke-influenced urban grime collected in Calgary and Kamloops, Canada. The potential influence of wildfire emissions on urban population centers is likely to grow, and grime can act as a pollutant reservoir in urban areas. I show that the influx of wildfire smoke into urban areas is reflected in changes in the grime PAH composition, providing evidence that the pollutants in passing wildfire plumes are retained in the urban environment long after the conclusion of a wildfire smoke event. In the second part, I further probe the persistence of wildfire and anthropogenic PAHs in the urban environment by collecting urban grime samples in seven Canadian and US cities. I show that grime PAHs continue to accumulate over a six-month period, confirming that grime can be a long-term PAH reservoir in urban areas. I demonstrate that wildfires can be the dominant source of grime PAHs and provide field evidence that the grime uptake of wildfire PAHs cannot occur without preexisting grime present, suggesting that more polluted urban areas are more susceptible to wildfire smoke influence. In the third part, I explore the effect of ozonation on wildfire ash PAH degradation, which is currently unknown. I show that changes in ozone concentration, ozone exposure time, and relative humidity does little to reduce the PAH mass loadings in wildfire ash, suggesting that PAHs in aged wildfire ash is recalcitrant. The recalcitrance is found to stem from PAH sequestration deep within the particle matrix, making the PAHs inaccessible to oxidants. This means that these ash PAHs will likely be persistent for long periods of time in the environment but may not necessarily be a hazard. Wildfire emissions are a current and ongoing concern, and there are still knowledge gaps regarding their persistence and fate in the environment. This thesis presents new insights into wildfire PAHs, which enhances our understanding of their impact in wildfire-affected areas.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 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".