Measurements of HO<sub>2</sub> uptake to aqueous aerosol: Mass accommodation coefficients and net reactive loss
Bibliographic record
Abstract
We present room temperature measurements of HO2 uptake to aqueous submicron aerosol obtained with an entrained aerosol flow tube coupled to a chemical ionization mass spectrometer. Two aqueous aerosol types were examined, H2SO4 at 35–40% relative humidity (RH) and (NH4)2SO4 at 40–45% RH. By doping the aerosol with Cu(II) (∼0.1 M in aerosol) to create an efficient aerosol sink, we determine lower limits to the mass accommodation coefficient, αHO2, to be 0.8 ± 0.3 for H2SO4 and 0.5 ± 0.1 for (NH4)2SO4 particles. In the absence of Cu(II), net reactive loss of HO2 on H2SO4 aerosol was slow, and we measured a reaction probability, γHO2, less than 0.01. In contrast, loss of HO2 to (NH4)2SO4 aerosol, buffered to pH = 5.1 but without Cu(II), was efficient in our experiment. For this system, aerosol‐induced loss of gas‐phase HO2 was observed to follow second‐order kinetics, and we infer from our measurements a second‐order aqueous phase reaction rate coefficient of 1 ± 0.25 × 107M−1 s−1 in good agreement with an estimate of 2 ± 1 × 107M−1 s−1 based on literature values of HO2 aqueous‐phase chemical parameters. These results imply that heterogeneous loss of HO2 to submicron aqueous sulfate aerosol will be strongly temperature dependent with negligible contribution to odd hydrogen radical (HOx) removal rates at temperatures warmer than ∼270 K, but potentially large contributions to HOx loss (e.g., >50% of total HOx loss) in colder regions of the troposphere depending on the available aqueous aerosol volume.
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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) | 0.001 | 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".