Potentially Important Contribution of Gas-Phase Oxidation of Naphthalene and Methylnaphthalene to Secondary Organic Aerosol during Haze Events in Beijing

Abstract

Naphthalene (Nap) and methylnaphthalene (MN) are the most abundant polycyclic aromatic hydrocarbons (PAHs) in atmosphere and have been proposed to be important precursors of anthropogenic secondary organic aerosol (SOA) derived from laboratory chamber experiments. In this study, atmospheric Nap/MN and their gas-phase photooxidation products were quantified by a Proton Transfer Reaction-Quadrupole interface Time-of-Flight Mass Spectrometer (PTR-QiTOF) during the 2016 winter in Beijing. Phthalic anhydride, a late generation product from Nap under high-NO x conditions, appeared to be more prominent than 2-formylcinnamaldehyde (early generation product), possibly due to more sufficient oxidation during the haze. 1,2-Phthalic acid (1,2-PhA), the hydrated form of phthalic anhydride, was capable of partitioning into aerosol phase and served as a tracer to explore the contribution of Nap to ambient SOA. The measured fraction in particle phase (F p) of 1,2-PhA averaged at 73 ± 13% with OA mass loadings of 52.5–87.8 μg/m3, lower than the value predicted by the absorptive partitioning model (100%). Using tracer product-based and precursor consumption-based methods, 2-ring PAHs (Nap and MN) were estimated to produce 14.9% (an upper limit) of the SOA formed in the afternoon during the wintertime haze, suggesting a comparable contribution of Nap and MN with monocyclic-aromatics on urban SOA formation.

Measurements of higher alkanes using NO<sup>+</sup>PTR-ToF-MS: significant contributions of higher alkanes to secondary organic aerosols in China

“…In this study, we determine 2.8±4.6% of SOA in PRD and 11.1±14.3% of SOA in NCP are contributed by naphthalenes. The SOA contribution from naphthalenes determined for NCP is comparable to the results (10.2±1.0%) obtained during haze events in Beijing in a recent study (Huang et al, 2019). Significant contribution from monoterpenes to SOA (8.7±14.6%)…”

“…PTR-MS using H3O + chemistry makes possible of quantitative of alkenes, aromatics, and even oxygenated VOCs (Yuan et al, 2017a). Here, PTR-MS with NO + chemistry was used to detect higher alkanes, through hydride abstraction by NO + forming mass (m-1) ions (m is the molecular mass) (Erickson et al, 2014;Koss et al, 2016;Inomata et al, 2013).…”

“…Although H3O + PTR-MS is response to large alkanes (>C8), these alkanes usually fragment into small masses with mass spectra difficult to interpret (Jobson et al, 2005;Gueneron et al, 2015). Recently, PTR-MS using NO + as reagent ions was demonstrated to provide fast online measurement of higher alkanes (Erickson et al, 2014;Koss et al, 2016;Inomata et al, 2013). The high-time resolution measurements of higher alkanes provide valuable information for SOA estimation, as the dependence of SOA yields on organic aerosol concentrations and other environmental parameters (e.g.…”

Urban organic aerosol composition in Eastern China differs from North to South: Molecular insight from a liquid chromatography-Orbitrap mass spectrometry study

“…In addition, through mass spectrometric analysis of individual compounds, we find that for the Changchun− samples, formulas of C8H6O4, C7H6O2, C7H6O3, C8H8O2, and C8H8O3 with DBE values of 6, 5, 5, 5, and 5 dominate the assigned CHO formulas with respect to peak abundance. According to previous studies, C8H6O4, C7H6O2 and C7H6O3 are suggested to be phthalic acid, benzoic acid and monohydroxy benzoic acid, respectively, which are derived from naphthalene (Kautzman et al, 2010;Riva et al, 2015;Wang et al, 2017;He et al, 2018;Huang et al, 2019). C8H8O2 and C8H8O3 are likely 4-hydroxy acetophenone and 4-methoxybenzoic acid which could be derived from estragole (Lee et al, 2006;Pereira et al, 2014).…”

Characterization of Anthropogenic Organic Aerosols by TOF-ACSM with the New Capture Vaporizer

“…Detailed descriptions about the PTR-QiTOF measurements are provided elsewhere (Huang et al, 2019). The meteorological parameters including temperature, RH, barometric pressure, wind speed, and wind direction were acquired by a weather station at the same site (Met One Instruments Inc., 083E, 092, 010C, and 020C).…”