The Role of Indoor Surface pH in Controlling the Fate of Acids and Bases in an Unoccupied Residence
Bibliographic record
Abstract
The chemical composition of indoor air is strongly driven by the composition and properties of indoor surfaces. At the Chemical Assessments of Surfaces and Air (CASA) campaign, we performed controlled additions of ammonia (reaching up to 297 ppb to 662 ppb) to investigate the impacts of changing surface basicity on the fate of gaseous and particulate acids and bases in an unoccupied house. In response to ammonia injections, nitrogen-containing compounds (C 2–7 H 3–11 N 1 O 0–3 ) were emitted from surfaces to the gas phase with signals increasing 10 1 % to 10 4 % compared to their signals prior to ammonia addition. At the same time, oxygen-containing compounds (C 1–7 H 2–6 O 2–3 ) were removed from the gas phase by indoor surface partitioning. Indoor surface pH and aerosol pH likely increased during these controlled ammonia injections relative to their baseline conditions. We estimate indoor surface pH to be nearly 5 and indoor aerosol pH to range from 2 to 4 during this experiment. At each ammonia injection, we observed ammonium and nitrate concentrations in the aerosol phase to increase due to gas-particle partitioning of ammonia and nitric acid. This gas-particle-surface exchange showed strong dependence on relative humidity; evaporation of gaseous bases was more pronounced at lower relative humidity when surface-associated water volume was reduced, while gas-to-particle partitioning of inorganic species was greater in the presence of more aerosol liquid water at higher relative humidity. From cooking experiments, which represent realistic sources of acids and bases to the indoor environment but which emit 10 times less ammonia than was introduced to the house via pure ammonia injection experiments, we predict that surfaces may still be important sources of these basic gases to indoor air.
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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".