Molecular corridors and parameterizations of volatility in the chemical evolution of organic aerosols

Abstract

Abstract. The formation and aging of organic aerosols (OA) proceed through multiple steps of chemical reaction and mass transport in the gas and particle phases, which is challenging for the interpretation of field measurements and laboratory experiments as well as accurate representation of OA evolution in atmospheric aerosol models. Based on data from over 30 000 compounds, we show that organic compounds with a wide variety of functional groups fall into molecular corridors, characterized by a tight inverse correlation between molar mass and volatility. We developed parameterizations to predict the saturation mass concentration of organic compounds containing oxygen, nitrogen, and sulfur from the elemental composition that can be measured by soft-ionization high-resolution mass spectrometry. Field measurement data from new particle formation events, biomass burning, cloud/fog processing, and indoor environments were mapped into molecular corridors to characterize the chemical nature of the observed OA components. We found that less-oxidized indoor OA are constrained to a corridor of low molar mass and high volatility, whereas highly oxygenated compounds in atmospheric water extend to high molar mass and low volatility. Among the nitrogen- and sulfur-containing compounds identified in atmospheric aerosols, amines tend to exhibit low molar mass and high volatility, whereas organonitrates and organosulfates follow high O : C corridors extending to high molar mass and low volatility. We suggest that the consideration of molar mass and molecular corridors can help to constrain volatility and particle-phase state in the modeling of OA particularly for nitrogen- and sulfur-containing compounds.

Simulating Aqueous-Phase Isoprene-Epoxydiol (IEPOX) Secondary Organic Aerosol Production During the 2013 Southern Oxidant and Aerosol Study (SOAS)

“…Repartitioning of tracers back to the gas phase is not considered in this study. Organosulfates are expected to have very low volatility, with a vapor pressure of 1.7 × 10 −8 Torr at ambient temperature (estimated using eqs 1 and 2 by Li et al 32 ). There is considerable uncertainty surrounding the gas-particle partitioning of tetrols.…”

Non-methane organic gas emissions from biomass burning: identification, quantification, and emission factors from PTR-ToF during the FIREX 2016 laboratory experiment

“…We determined the saturation vapor concentration (C 0 , in µg m −3 at 25 • C) for each of the identified and unidentified species. The values were taken from databases (CRC Handbook, NIST Chemistry WebBook, Yaws, 2015) or estimated based on elemental composition via the parameterization described by Li et al (2016). Species emitted from lower-temperature processes during the fire have a higher fraction of compounds with low volatility compared to the high-temperature processes (later and earlier in the fire shown in Fig.…”

Lower than expected volatility of secondary organic aerosols formed during α-pinene ozonolysis

“…However, Li et al (2016) parameterized log 10 C * as a function of the number of carbon and oxygen atoms (2D function). The 2D function was fitted to EVAPORATION data for various oxygenated organic compounds.…”

“…Using these techniques revealed that the major particle products from α-pinene ozonolysis are highly oxygenated molecules (HOMs), ester dimers, and semi-volatile compounds (Zhang et al, 2015;. Recent studies on the parameterization of saturation concentration (Shiraiwa et al, 2014;Li et al, 2016) and the sensitivity of electrospray ionization mass spectrometry (Kruve et al, 2013;Heinritzi et al, 2016) is helpful to evaluate SOA volatility using mass analysis data. 50…”