Photolysis and Heterogeneous Reaction of Coniferyl Aldehyde Adsorbed on Silica Particles with Ozone

Abstract

The pseudo-first-order loss of coniferyl aldehyde, adsorbed on silicon dioxide particles, upon heterogeneous ozonolysis was monitored at various ozone mixing ratios in the absence and presence of simulated sunlight. For the first time we investigated the effect of light on the heterogeneous ozonolysis of coniferyl aldehyde adsorbed on silica particles. We found that UV-VIS light (λ>300 nm) does not impact the degradation of coniferyl aldehyde by ozone but induces an additional, slow photolysis of the aldehyde with a photolytic rate constant of ~10(-5) s(-1). In both cases, that is, in presence and/or absence of light, the heterogeneous ozonation kinetics are well described by an immediate gas-surface reaction formalism with light-independent rate constants of k(2nd)=(7.2±0.9)×10(-19) cm(3) molec(-1) s(-1) and (7.6±1.7)×10(-19) cm(3) molec(-1) s(-1) in the absence and presence of light, respectively. Five oxidation products: glycolic acid, oxalic acid, vanillin, vanillic acid and 3,4-dihydroxybenzoic acid were identified and confirmed by their corresponding standards. Vanillin and vanillic acid absorb light in the region λ>300 nm and thus can further participate in the direct and indirect photolysis processes of atmospheric relevance. A reaction mechanism is proposed in order to elucidate the ozonolysis reaction and to explain the reaction products.

Heterogeneous reactions of ozone with commonly used pesticides adsorbed on silica particles

“…1). This experimental setup was initially developed by Net et al (2009) and an important number of ozone heterogeneous reactions have been studied (e.g., Net et al, 2010aNet et al, , 2010bNet et al, , 2010cNet et al, , 2010dNet et al, , 2011. Later on, Pflieger et al have adapted to study the heterogeneous reactions of pesticides and successfully validated by intercomparison with the flowtube reactor with trifluralin, a dinitroaniline herbicide (Pflieger et al, 2011).…”

“…The atmospheric mineral aerosols can be mimicked with commercial silica particles such as AEROSIL R812 (Barbas et al, 1996;Net et al, 2009Net et al, , 2010aNet et al, , 2010bNet et al, , 2010cNet et al, , 2010dNieto-Gligorovski et al, 2010;Pflieger et al, , 2011Pflieger et al, , 2012. In this study, the hydrophobic silica particles (AEROSIL R812, Degussa, purity SiO 2 content !99.8%, average primary particle size of 7 nm and specific surface area (BET) of 260 ± 30 m 2 g À1 ) were coated with the pesticides under study according to a liquid/solid adsorption.…”

Chemical composition of PM<sub>2.5</sub> in October 2017 Northern California wildfire plumes

“…The emission, exposure, and health impacts of PAHs in biomass burning have received a great deal of attention in previous studies (Shen et al, 2013;Sun et al, 2018;Tuet et al, 2019). However, other groups of compounds, such as monocyclic aromatic compounds including hydroquinone, catechol, and cinnamaldehyde (Leanderson and Tagesson, 1990;Muthumalage et al, 2018), may also make substantial contributions to the toxicity of biomass burning smoke. The effect of compounds other than PAHs may be worthy of attention in future toxicological studies of BBOA.…”

“…Protocatechuic acid and gallic acid are likely more specific to biomass burning. Protocatechuic acid is a product of coniferyl alcohol and coniferyl aldehyde ozonolysis and of the vanillic acid + NO 3 reaction (Liu et al, 2012;Net et al, 2010Net et al, , 2011. Protocatechuic acid and gallic acids were also found to be the Fentonlike oxidation products of biomass burning-related small aromatic acids in the atmospheric aqueous phase (Santos et al, 2016a, b).…”

Chemical Composition of PM<sub>2.5</sub> in October 2017 Northern California Wildfire Plumes

“…alcohol and coniferyl aldehyde ozonolysis, and the vanillic acid + NO3 reaction (Liu et al, 2012;Net et al, 2010Net et al, , 2011.…”