Catalytic role of formaldehyde in particulate matter formation

Formaldehyde (HCHO), the simplest and most abundant carbonyl in the atmosphere, contributes to particulate matter (PM) formation via two in-cloud processing pathways. First, in a catalytic pathway, HCHO reacts with hydrogen peroxide (H₂O₂) to form hydroxymethyl hydroperoxide (HMHP), which rapidly ox...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2022-02, Vol.119 (6), p.1-9
Main Authors: Dovrou, Eleni, Bates, Kelvin H., Moch, Jonathan M., Mickley, Loretta J., Jacob, Daniel J., Keutsch, Frank N.
Format: Article
Language:English
Subjects:
Carbonyl compounds
Carbonyls
Chemical transport
Formaldehyde
Hydrogen peroxide
Hydroxyl radicals
Isoprene
Oxidation
Particulate emissions
Particulate matter
Physical Sciences
Sulfates
Sulfur
Sulfur dioxide
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Summary:Formaldehyde (HCHO), the simplest and most abundant carbonyl in the atmosphere, contributes to particulate matter (PM) formation via two in-cloud processing pathways. First, in a catalytic pathway, HCHO reacts with hydrogen peroxide (H₂O₂) to form hydroxymethyl hydroperoxide (HMHP), which rapidly oxidizes dissolved sulfur dioxide (SO2,aq) to sulfate, regenerating HCHO. Second, HCHO reacts with dissolved SO2,aq to form hydroxymethanesulfonate (HMS), which upon oxidation with the hydroxyl radical (OH) forms sulfate and also reforms HCHO. Chemical transport model simulations using rate coefficients from laboratory studies of the reaction rate of HMHP with SO2,aq show that the HMHP pathways reduce the SO₂ lifetime by up to a factor of 2 and contribute up to ∼18% of global sulfate. This contribution rises to >50% in isoprene-dominated regions such as the Amazon. Combined with recent results on HMS, this work demonstrates that the one-carbon molecules HMHP and HCHO contribute significantly to global PM, with HCHO playing a crucial catalytic role.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.2113265119