Aqueous-phase photochemical oxidation and direct photolysis of vanillin – a model compound of methoxy phenols from biomass burning
Bibliographic record
Abstract
Abstract. We present here experimental results on aqueous-phase (A) photochemical oxidation (with UV and OH radicals generated from H2O2 photolysis) and (B) direct photolysis (with only UV irradiation) of a methoxy phenol, vanillin (VL), as a model compound from biomass burning. Both on-line aerosol mass spectrometric (AMS) characterization and off-line chemical analyses were performed. AMS analyses of dried atomized droplets of the bulk reacting mixtures showed that VL almost entirely evaporates during the drying process. Large amounts of organic mass remained in the particle phase after reactions under both conditions. Under condition (A), AMS measured organic mass first increased rapidly and then decreased, attributable to the formation of non-volatile products and subsequent formation of smaller and volatile products, respectively. The oxygen-to-carbon (O : C) ratio of the products reached 1.5 after about 80 min, but dropped substantially thereafter. In contrast, organic mass increased slowly under condition (B). The O : C ratio reached 1.0 after 180 min. In off-line analyses, small oxygenates were detected under condition (A), while hydroxylated products and dimers of VL were detected under condition (B). Particle hygroscopic growth factor (GF) and cloud condensation nuclei (CCN) activity of the reacting mixtures were found to depend on both organic volume fraction and the degree of oxygenation of organics. Results show that (1) aqueous-phase processes can lead to the retention of a large portion of the organic mass in the particle phase; (2) once retained, this portion of organic mass significantly changes the hygroscopicity and CCN activity of the aerosol particles; (3) intensive photochemical oxidation gave rise to an O : C ratio as high as 1.5 but the ratio decreased as further oxidation led to smaller and more volatile products; and (4) polymerization occurred with direct photolysis, resulting in high-molecular-weight products of a yellowish color. This study demonstrates that aqueous-phase reactions of a methoxy phenol can lead to substantial amount of secondary organic aerosol (SOA) formation. Given the vast amount of biomass burning input globally, model representation of either the SOA budget or their subsequent effects would not be adequate if the contribution of SOA formation from aqueous-phase reactions of methoxy phenols is not considered.
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 distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 teacher head, 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".