Heterogeneous Formation of Organonitrates (ON) and Nitroxy-Organosulfates (NOS) from Adsorbed α-Pinene-Derived Organosulfates (OS) on Mineral Surfaces

Abstract

Organonitrates (ON) and nitroxy-organosulfates (NOS) are important components of secondary organic aerosols (SOAs). Gas-phase reactions of α-pinene (C 10 H 16 ), a primary precursor for several ON compounds, are fairly well understood although formation pathways for NOS largely remain unknown. NOS formation may occur via reactions of ON and organic peroxides with sulfates as well as through radical-initiated photochemical processes. Despite the fact that organosulfates (OS) represent a significant portion of the organic aerosol mass, ON and NOS formation from OS is less understood, especially through nighttime heterogeneous and multiphase chemistry pathways. In the current study, surface reactions of adsorbed αpinene-derived OS with nitrogen oxides on hematite and kaolinite surfaces, common components of mineral dust, have been investigated. α-Pinene reacts with sulfated mineral surfaces, forming a range of OS compounds on the surface. These OS compounds when adsorbed on mineral surfaces can further react with HNO 3 and NO 2 , producing several ON and NOS compounds as well as several oxidation products. Overall, this study reveals the complexity of reactions of prevalent organic compounds leading to the formation of OS, ON, and NOS via heterogeneous and multiphase reaction pathways on mineral surfaces. It is also shown that this chemistry is mineralogy-specific.

Heterogeneous Reactions of Phenol on Different Components of Mineral Dust Aerosol: Formation of Oxidized Organic and Nitro-Phenolic Compounds

“…Furthermore, unlike with phenol-exposed nitrated-α-Fe 2 O 3 surfaces, here, a loss of surface hydroxyl groups was observed by a decrease in intensity of peaks at 3620 and 3674 cm –1 , suggesting strong interactions between the surface OH groups and SO 2 ( g ). 90 These surface products were solvent extracted and analyzed using HRMS to better understand and elucidate these surface products.…”

Heterogeneous chemistry of methyl ethyl ketone on mineral oxide surfaces: impacts of relative humidity and nitrogen dioxide on product formation

“…Transmission FTIR spectroscopy was used to monitor reactions on oxide surfaces at 296 ± 1 K. Additional details of the infrared cell and gas handling system have been previously described. [47][48][49][50][51][52] Oxide particles (SiO 2 , Aerosil OX50, a-Fe 2 O 3 , hematite, 99+%, Fischer Scientic, and TiO 2 , rutile, Sigma Aldrich) with a BET surface area of 30 + 1 m 2 g −1 , 80 + 10 m 2 g −1 , and 31 + 4 m 2 g −1 , respectively, were heated in an oven at 473 ± 1 K overnight to remove organic contaminants and then pressed onto one half of a tungsten grid (ca. 5 mg).…”

Beyond the formation: unveiling the atmospheric transformation of organosulfatesviaheterogeneous OH oxidation

“…The heterogeneous formation pathway of OSs is mediated by reactions of gaseous sulfur dioxide (SO 2 ) with unsaturated hydrocarbons such as alkenes, carboxylic acids, and aromatic compounds near the aerosol surface. [30][31][32][33][34][35] Formation pathways via aqueous-phase reactions in general begin with the reactive uptake of gas-phase organic species (e.g., isoprene-derived epoxides and hydroperoxides), formed upon the photochemical oxidation of various VOCs, onto pre-existing sulfate aerosols; following this, OSs can be obtained from aqueous-phase reactions such as acid-catalyzed ring-opening of epoxides and sulfate esterification. 8,10,34,[36][37][38][39][40][41][42][43] Other important processes are nucleophilic substitution of tertiary organonitrates by SO 4 2À , 44,45 and addition of sulfoxy radical anions (i.e., sulfite (SO 3…”