Insights into Secondary Organic Aerosol Formation Mechanisms from Measured Gas/Particle Partitioning of Specific Organic Tracer Compounds

Abstract

In situ measurements of organic compounds in both gas and particle phases were made with a thermal desorption aerosol gas chromatography (TAG) instrument. The gas/particle partitioning of phthalic acid, pinonaldehyde, and 6,10,14-trimethyl-2-pentadecanone is discussed in detail to explore secondary organic aerosol (SOA) formation mechanisms. Measured fractions in the particle phase (f(part)) of 6,10,14-trimethyl-2-pentadecanone were similar to those expected from the absorptive gas/particle partitioning theory, suggesting that its partitioning is dominated by absorption processes. However, f(part) of phthalic acid and pinonaldehyde were substantially higher than predicted. The formation of low-volatility products from reactions of phthalic acid with ammonia is proposed as one possible mechanism to explain the high f(part) of phthalic acid. The observations of particle-phase pinonaldehyde when inorganic acids were fully neutralized indicate that inorganic acids are not required for the occurrence of reactive uptake of pinonaldehyde on particles. The observed relationship between f(part) of pinonaldehyde and relative humidity suggests that the aerosol water plays a significant role in the formation of particle-phase pinonaldehyde. Our results clearly show it is necessary to include multiple gas/particle partitioning pathways in models to predict SOA and multiple SOA tracers in source apportionment models to reconstruct SOA.

The Molecular Identification of Organic Compounds in the Atmosphere: State of the Art and Challenges

“…and for studying SOA gas-to-particle partitioning compounds, 405 OA aging/gas-to-particle partitioning of semi-volatile VOCs in source apportionment models (CMB and PMF), 406 and reactions contributing to ambient OA. 377 Source apportionment in time-resolution of minutes can be achieved with the AMS technique while classical filter collection techniques provide the same information with a frequency of about a day.…”

Introductory lecture: atmospheric chemistry in the Anthropocene

“…353,363,366,367,369,374,[380][381][382][383] However, analysis of SOA composition in some eld studies suggests that more volatile products can be found in SOA than expected based on their volatility. 384 This may be related to the particle phase and growth mechanisms. Understanding the phase of organic particles is important for quantifying exchange with the gas phase, understanding water uptake, describing the chemistry in the bulk and on the surface, and being able to predict the growth and composition of SOA in air.…”

Development of an automated high-temperature valveless injection system for online gas chromatography

“…The first, hereafter referred to as Instrument 1, introduced the prototype version of the VLI along with a vapor-phase denuder for the study of gas-particle partitioning (Zhao et al, 2013b). Instrument 1 was deployed during the Research in California at the Nexus of Air Quality and Climate Change (CalNex) campaign from 31 May to 27 June 2010.…”

“…Ambient samples were acquired at 9 L min −1 for two durations: 90 min from 31 May to 9 June and 30 min from 10 to 27 June. Further details of the sample collection and analysis can be found elsewhere (Zhao et al, 2013b). Field-based evaluations of the VLI performance during this study were based on the use of perdeuterated internal standards (n-alkanes and poly aromatic hydrocarbons; C/D/N Isotopes) manually injected on top of ambient samples at an average rate of 1.6 per day throughout the 29 days of continuous sampling.…”

“…The prototype VLI was first deployed in the TAG instrument during a 2010 California air quality study (CalNex) (Zhao et al, 2013b). During the course of 4 weeks of continuous sampling, 63 manual liquid-based internal standard injections were made on top of regular ambient samples at the average rate of 1.6 per day.…”