Reactions between Criegee Intermediates and the Inorganic Acids HCl and HNO₃: Kinetics and Atmospheric Implications

Abstract

Criegee intermediates (CIs) are a class of reactive radicals that are thought to play a key role in atmospheric chemistry through reactions with trace species that can lead to aerosol particle formation. Recent work has suggested that water vapor is likely to be the dominant sink for some CIs, although reactions with trace species that are sufficiently rapid can be locally competitive. Herein, we use broadband transient absorption spectroscopy to measure rate constants for the reactions of the simplest CI, CH2OO, with two inorganic acids, HCl and HNO3, both of which are present in polluted urban atmospheres. Both reactions are fast; at 295 K, the reactions of CH2OO with HCl and HNO3 have rate constants of 4.6×10−11 cm3 s−1 and 5.4×10−10 cm3 s−1, respectively. Complementary quantum‐chemical calculations show that these reactions form substituted hydroperoxides with no energy barrier. The results suggest that reactions of CIs with HNO3 in particular are likely to be competitive with those with water vapor in polluted urban areas under conditions of modest relative humidity.

Spectroscopic Characterization of the Reaction Products between the Criegee Intermediate CH2OO and HCl

“…HCl has both biogenic and anthropogenic sources existing in the troposphere at mixing ratios similar to those of SO 2 , and has recently been proposed as a SCI sink . The simplest Criegee intermediate, CH 2 OO, and HCl reaction has been investigated by ab initio calculations, and its rate constant has been measured . However, there is not any experimental evidence about the nature of the primary reaction products that can provide valuable information for understanding the detailed reaction mechanism.…”

Estimating the atmospheric concentration of Criegee intermediates and their possible interference in a FAGE-LIF instrument

“…The rate coefficient of SCIs with SO 2 was determined by several groups at (3.3 ± 2.0) × 10 −11 cm 3 molecule −1 s −1 (Welz et al, 2012;Liu et al, 2014b;Sheps et al, 2014;Stone et al, 2014;Chhantyal-Pun et al, 2015;Newland et al, 2015a, b;Foreman et al, 2016;Zhu et al, 2016). An earlier, lower value of ∼ 5.0 × 10 −13 cm 3 molecule −1 s −1 (Mauldin III et al, 2012;Berndt et al, 2012) appears to be hard to reconcile with the remaining literature, as extensively discussed in the Supplement.…”

UV photodissociation dynamics of CHI2Cl and its role as a photolytic precursor for a chlorinated Criegee intermediate

“…44,53 A pulsed Nd:YAG laser was used to photodissociate CHI2Cl in the presence of excess O2 at 355 nm and 266 nm (7±1 mJ pulse -1 ). Spectra were recorded at 15 Torr total pressure with the gas mixture comprising 0.02% CHI2Cl, 10% O2 and N2 balance.…”