Methanediol from cloud-processed formaldehyde is only a minor source of atmospheric formic acid
| dc.contributor.author | Nguyen, T.L . | |
| dc.contributor.author | Peeters, J . | |
| dc.contributor.author | Müller, J.-F . | |
| dc.contributor.author | Perera, A . | |
| dc.contributor.author | Bross, D.H . | |
| dc.contributor.author | Ruscic, B . | |
| dc.contributor.author | Stanton, J.F. | |
| dc.date | 2023 | |
| dc.date.accessioned | 2023-11-24T08:57:57Z | |
| dc.date.available | 2023-11-24T08:57:57Z | |
| dc.identifier.uri | https://orfeo.belnet.be/handle/internal/11188 | |
| dc.description | Atmospheric formic acid is severely underpredicted by models. A recent study proposed that this discrepancy can be resolved by abundant formic acid production from the reaction (1) between hydroxyl radical and methanediol derived from in-cloud formaldehyde processing and provided a chamber-experiment-derived rate constant, k1 = 7.5 × 10−12 cm3 s−1. High-level accuracy coupled cluster calculations in combination with E,J-resolved two-dimensional master equation analyses yield k1 = (2.4 ± 0.5) × 10−12 cm3 s−1 for relevant atmospheric conditions (T = 260–310 K and P = 0–1 atm). We attribute this significant discrepancy to HCOOH formation from other molecules in the chamber experiments. More importantly, we show that reversible aqueous processes result indirectly in the equilibration on a 10 min. time scale of the gas-phase reaction HCHO+H2O⇌HOCH2OH (2) with a HOCH2OH to HCHO ratio of only ca. 2\%. Although HOCH2OH outgassing upon cloud evaporation typically increases this ratio by a factor of 1.5–5, as determined by numerical simulations, its in-cloud reprocessing is shown using a global model to strongly limit the gas-phase sink and the resulting production of formic acid. Based on the combined findings in this work, we derive a range of 1.2–8.5 Tg/y for the global HCOOH production from cloud-derived HOCH2OH reacting with OH. The best estimate, 3.3 Tg/y, is about 30 times less than recently reported. The theoretical equilibrium constant Keq (2) determined in this work also allows us to estimate the Henry’s law constant of methanediol (8.1 × 105 M atm−1 at 280 K). | |
| dc.language | eng | |
| dc.title | Methanediol from cloud-processed formaldehyde is only a minor source of atmospheric formic acid | |
| dc.type | Article | |
| dc.subject.frascati | Earth and related Environmental sciences | |
| dc.audience | Scientific | |
| dc.source.title | Proceedings of the National Academy of Sciences | |
| dc.source.volume | 120 | |
| dc.source.issue | 48 | |
| dc.source.page | e2304650120 | |
| Orfeo.peerreviewed | Yes | |
| dc.identifier.doi | 10.1073/pnas.2304650120 | |
| dc.identifier.url |
