Impact of Criegee Intermediate Reactions with Peroxy Radicals on Tropospheric Organic Aerosol

Abstract

Peroxy radicals and carbonyl oxides (Criegee intermediates) are produced in the troposphere during OH and ozone-initiated oxidation of hydrocarbons. Reactions between these species have previously been shown to form highly oxidized molecules which can condense to form secondary organic aerosols. Here, cavity ring-down spectroscopy coupled with laser flash photolysis was used to measure directly rate coefficients for reactions of CH2OO with CH3O2 and CH3C(O)O2. The rate coefficients were found to be similar within the measurement uncertainties and only weakly dependent on temperature (in the range 243 -310 K) and pressure (10 -100 Torr, N2). A combined rate coefficient of k (CH2OO+RO2, RO2 = CH3O2/CH3C(O)O2) = (2.4 ± 1.2) × 10 -11 cm 3 molecule -1 s -1 was obtained under these conditions. Global modelling 2 using STOCHEM-CRI, updated with monoterpene chemistry generating Criegee intermediates, and supplemented by regional box modelling, shows that this class of Criegee intermediate + peroxy radical reactions can contribute up to ~1.3% of secondary organic aerosol production in forested regions of the world. (CH ) CO ⎯⎯⎯ CH + CH C(O) R1 CH + O (+M) → CH O (+M) R2, k2 = 7×10 -31 (T/300) (-3±1) [M] CH C(O) + O (+M) → CH C(O)O + (M) R3, k3 (see text) CH C(O) + O (+M) → OH + C H O + (M) R4, k4 (see text) CH O + CH O → 2CH O + O R5, k5 = 7.4×10 -13 exp(520±300/T) CH O + CH O → CH OH + HCHO + O R6, k6 = 1.03×10 -13 exp(365±200/T) -k5 CH C(O)O + CH C(O)O → 2CH + 2CO + O R7, k7 = 2.9×10 -12 exp(500±200/T) CH O + CH C(O)O → CH O + CH + CO + O R8, k8 = 0.9×2×10 -12 exp(500±250/T) CH O + CH C(O)O → CH COOH + HCHO + O R9, k9 = 0.1×2×10 -12 exp(500±250/T)

Low-temperature reaction dynamics of paramagnetic species in the gas phase

“…For example, reactions between peroxy radicals and carbonyl oxides (also known as Criegee intermediates), which can lead to the formation of secondary organic aerosols in the troposphere, have recently been studied using cavity ring-down spectroscopy combined with laser flash photolysis in a flow cell. 131 Readers are directed to a recent review article discussing the chemistry of Criegee intermediates for further details on these atmospherically important reaction pathways. 132 Flow-based methods have provided a vast amount of experimental data on radical reactions over a range of temperatures—with many of the reaction properties incorporated into databases developed for astronomical and atmospheric modelling.…”

Investigation of the Production of Trifluoroacetic Acid from Two Halocarbons, HFC-134a and HFO-1234yf and Its Fates Using a Global Three-Dimensional Chemical Transport Model

“…Although the global tropospheric lifetime of TFA is consistent between simulations, the addition of the updated Criegee intermediate chemistry results in significant regional surface lifetime reductions. SCIs exist in the greatest concentrations over forested regions, where biogenic alkene emissions are high, 48 and thus significant impacts on TFA lifetimes are seen over the Amazon, boreal, and Congo forests, as shown in Figure 2b. SCI-mediated loss of TFA is significant over land masses, but it is mostly negligible over water and ice-covered regions.…”

“…19 SCI production can also be significant in urban areas if the emissions of anthropogenic volatile organic compounds (VOCs) are high. 20 Chhantyal-Pun et al 21 reported the temperature-dependent rate constants of the reactions of TFA with selected SCIs and showed them to exceed the gas-kinetic limit. From this, it is clear these intermediates are likely to make a significant contribution to, if not dictate, the atmospheric fate of TFA.…”

Criegee intermediates: production, detection and reactivity

“…Similar to reactions with NO2, Criegee intermediate have been predicted to undergo addition reactions with RO2 with submerged barriers [157,168]. Recently, Chhantyal-Pun et al [169] measured rate coefficients for reaction of CH2OO with CH3O2 and CH3C(O)O2 of ~3× 10 -11 and ~5.0 × 10 -11 cm 3 molecule -1 s -1 at 293 K. Both rate coefficients were found to have a negative temperature dependence with values of (2-10) × 10 -11 cm 3 molecule -1 s -1 in the 310-240 K temperature range, consistent with the prediction of a submerged barrier. The adduct product from the reaction of the Criegee intermediate and peroxy radical is also predicted to be a peroxy radical (Scheme 8), which can further react with Criegee intermediates to form oligomerization products with Criegee intermediate units.…”

“…The MFOHPs produced from larger peroxy adducts can condense into secondary organic aerosol as shown in Scheme 5. The combined global chemistry transport modelling and box modelling studies of Chhantyal-Pun et al [169] showed maximum contributions of ≤3% to the SOA concentration in the Amazon region from reactions of Criegee intermediates with peroxy radicals. The fast reaction of Criegee intermediates with peroxy radicals could also be important in atmospheric simulation chamber experiments.…”