Guaiacol Nitration in a Simulated Atmospheric Aerosol with an Emphasis on Atmospheric Nitrophenol Formation Mechanisms

Abstract

Atmospheric nitrophenols are pollutants of concern due to their toxicity and light-absorption characteristics and their low reactivity resulting in relatively long residence times in the environment. We investigate multiphase nitrophenol formation from guaiacol in a simulated atmospheric aerosol and support observations with the corresponding chemical mechanisms. The maximal secondary organic aerosol (SOA) yield (42%) is obtained under illumination at 80% relative humidity. Among the identified nitrophenols, 4-nitrocatechol (3.6% yield) is the prevailing species in the particulate phase. The results point to the role of water in catechol and further 4-nitrocatechol formation from guaiacol. In addition, a new pathway of dark nitrophenol formation is suggested, which prevailed in dry air and roughly yielded 1% nitroguaiacols. Furthermore, the proposed mechanism possibly leads to oligomer formation via a phenoxy radical formation by oxidation with HONO.

Aqueous ·OH Oxidation of Highly Substituted Phenols as a Source of Secondary Organic Aerosol

“…However, because uncertainties are quite large (mostly because of uncertainty in the reference rate constants; Table S3), the rate constants at pH 2 and 5 (or 6) for highly substituted ArOH are not statistically different for a given phenol except for tyrosol. This may be because the rate constants of highly substituted ArOHs with · OH approach the diffusion limit …”

“…This may be because the rate constants of highly substituted ArOHs with • OH approach the diffusion limit. 52 To explore the pH dependence of the • OH rate constants, we measured phenol loss kinetics in solutions containing both GA and guaiacol (GUA) between pH 1 and 5 (Table S5). To account for differences in the photon flux, we divided the pseudo-first-order rate constants for loss of GA (k′ GA ) and GUA (k′ GUA ) by the photolysis rate constant (j 2NB ) of our chemical actinometer, 2-nitrobenzaldehyde, which we measured each experiment day.…”

Interfacial Ozone Oxidation Chemistry at a Riverine Surface Microlayer as a Source of Nitrogen Organic Compounds

“…Biomass burning (BB), for example, domestic solid fuel burning, emits a large amount of organic nitrogen (N)-containing organic compounds into the air in urban environments. − One fraction of the N-containing organics is associated with the so-called “brown carbon” (BrC) compounds that absorb in the visible range of the solar spectrum, thereby contributing to positive radiative forcing (warming the atmosphere). − (Photo)­chemical oxidation of phenolic substances occurring in the atmospheric aqueous phase (cloud, fog, and aerosol liquid water) − and heterogeneous processing of gas-phase ozone (O 3 ) with the methoxyphenols at the water surface can also contribute to the formation of N-containing organic compounds, including BrC, in the atmosphere.…”

Photolysis of nitrophenols in gas phase and aqueous environment: a potential daytime source for atmospheric nitrous acid (HONO)

“…[4][5][6][7][8] The produced OH• are important oxidants in the atmosphere and have a great impact on As the simplest nitro-aromatic compounds, nitrophenols (NPs), which can be formed from the oxidation of phenols under the high NO x conditions as well as combustions of fossil fuel and biomass, have received intensive research attentions, due to their great contributions to the formation of SOAs. 21,[28][29][30][31][32] NPs also show highly photo-absorption properties to solar radiation, which accounts for most of the visible part (50-80%, λ > 400 nm) and ~4% of the ultraviolet part (λ = ~370 nm), and contribute to photochemical reactions. [33][34][35][36] A high concentration of NPs has been observed in both gas phase (0.2-52 ng•m -3 ) and particle phase (0.08-768 ng•m -3 ), 23,[37][38][39][40][41] as well as the concentration of NPs in winter is higher than it in summer.…”