Insight Into the Molecular Photooxidation Evolution Mechanism of Brown Carbon Released From Residential Solid Fuel Combustion
Bibliographic record
Abstract
Abstract Solid fuels were one of the important emission sources of brown carbon (BrC). This study investigates molecular composition of BrC derived from combustion of five types of residential solid fuels (i.e., firewood, corn cob, bituminous coal, anthracite, and biomass briquette) and their photooxidation evolution mechanisms using an oxidation flow reactor. Results show that nitrogen‐containing and sulfur‐containing organic compounds are the main components of molecular composition of methanol‐soluble organic compounds (MSOC) emitted from these fuels, with their intensity being 33%–43% and 23%–56%, respectively, depending on fuel type. The photooxidation processes mediated by NO3⋅ and ⋅ OH significantly altered the molecular composition and distribution of aged MSOC. The formation of typical nitrogen‐containing BrC chromophores (e.g., nitro‐aromatic compounds) also proves the role of NO3 ⋅ in the photooxidation reaction. However, the photo‐enhancement effect of NO3 ⋅ mediated photooxidation reaction could not offset the destruction of the molecular conjugation degree and aromaticity of BrC by ⋅ OH oxidation, resulting in a significant reduction in the light absorption capacity of BrC. The mass absorption coefficient at 365 nm of BrC aged for 12 days derived from the remaining fuels decreased by 47.0%–55.8% compared to that of fresh BrC, except for firewood, which only decreased by 5.3%. These findings on the molecular evolution and oxidation mechanism of BrC generated from solid fuels are useful in reducing uncertainties in climate change studies involving BrC aerosol.
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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 | 0.000 | 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".