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Nguyen TL, Peeters J, Müller JF, Perera A, Bross DH, Ruscic B, Stanton JF. Methanediol from cloud-processed formaldehyde is only a minor source of atmospheric formic acid. Proc Natl Acad Sci U S A 2023; 120:e2304650120. [PMID: 37988470 PMCID: PMC10691333 DOI: 10.1073/pnas.2304650120] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 09/07/2023] [Indexed: 11/23/2023] Open
Abstract
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 [Formula: see text] (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).
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Affiliation(s)
- Thanh Lam Nguyen
- Quantum Theory Project, Department of Chemistry, University of Florida, Gainesville, FL32611
- Quantum Theory Project, Department of Physics, University of Florida, Gainesville, FL32611
| | - Jozef Peeters
- Department of Chemistry, University of Leuven, LeuvenB-3001, Belgium
| | - Jean-François Müller
- Department of Atmospheric Composition, Royal Belgian Institute for Space Aeronomy, BrusselsB-1180, Belgium
| | - Ajith Perera
- Quantum Theory Project, Department of Chemistry, University of Florida, Gainesville, FL32611
- Quantum Theory Project, Department of Physics, University of Florida, Gainesville, FL32611
| | - David H. Bross
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL60439
| | - Branko Ruscic
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL60439
| | - John F. Stanton
- Quantum Theory Project, Department of Chemistry, University of Florida, Gainesville, FL32611
- Quantum Theory Project, Department of Physics, University of Florida, Gainesville, FL32611
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Nguyen TL, Perera A, Peeters J. High-accuracy first-principles-based rate coefficients for the reaction of OH and CH 3OOH. Phys Chem Chem Phys 2022; 24:26684-26691. [DOI: 10.1039/d2cp03919b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The ˙OH-initiated oxidation of methyl hydroperoxide was theoretically characterized using high-accuracy composite amHEAT-345(Q) coupled-cluster calculations followed by a two-dimensional E,J resolved master equation analysis.
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Affiliation(s)
- Thanh Lam Nguyen
- Quantum Theory Project, Departments of Chemistry and Physics, University of Florida, Gainesville, FL, 32611, USA
| | - Ajith Perera
- Quantum Theory Project, Departments of Chemistry and Physics, University of Florida, Gainesville, FL, 32611, USA
| | - Jozef Peeters
- Department of Chemistry, University of Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium
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