Molecular Characterization of Oxygenated Organic Molecules and Their Dominating Roles in Particle Growth in Hong Kong

Abstract

Oxygenated organic molecules (OOMs) are critical intermediates linking volatile organic compound oxidation and secondary organic aerosol (SOA) formation. Yet, the understanding of OOM components, formation mechanism, and impacts are still limited, especially for urbanized regions with a cocktail of anthropogenic emissions. Herein, ambient measurements of OOMs were conducted at a regional background site in South China in 2018. The molecular characteristics of OOMs revealed dominant nitrogen-containing products, and the influences of different factors on OOM composition and oxidation state were elucidated. Positive matrix factorization analysis resolved the complex OOM species to factors featured with fingerprint species from different oxidation pathways. A new method was developed to identify the key functional groups of OOMs, which successfully classified the majority species into carbonyls (8%), hydroperoxides (7%), nitrates (17%), peroxyl nitrates (10%), dinitrates (13%), aromatic ring-retaining species (6%), and terpenes (7%). The volatility estimation of OOMs was improved based on their identified functional groups and was used to simulate the aerosol growth process contributed by the condensation of those low-volatile OOMs. The results demonstrate the predominant role of OOMs in contributing sub-100 nm particle growth and SOA formation and highlight the importance of dinitrates and anthropogenic products from multistep oxidation.

Molecular Composition of Anthropogenic Oxygenated Organic Molecules and Their Contribution to Organic Aerosol in a Coastal City

“…This serves as evidence that AOOMs were formed via photochemical reaction with locally sourced precursors in this coastal city. Figure b shows the concentration of AOOMs as a function of temperature and ozone photolysis frequency [ j (O 1 D)], which indicates that high temperature and intense radiation have a robust positive effect on the generation of AOOMs . Furthermore, as shown in Figure c and Table S7, the AOOM concentration in Xiamen and other sampling sites exhibited a temperature dependence.…”

“…The atmospheric environment observation supersite, located at this institute and approximately 80 m above ground level, was selected as the sampling site. This site is close to major traffic arteries with high traffic volumes, commercial properties, and residential areas, making it representative of a typical urban environment …”

“…The Nitrate-CI-APi-TOF (Aerodyne Research Inc., USA, and Tofwerk AG, Switzerland) was deployed to detect the OOMs . The calibration of OOMs is based on the calibration coefficients of sulfuric acid after mass transmission correction, which is the preferred method in the current study of OOMs. , Details of instrument setup, calibration, and uncertainty analysis of OOMs concentrations are given in Text S1. On the basis of the current knowledge of VOCs oxidation, a recently developed workflow was utilized to attribute these OOMs to their likely VOCs precursor classes, including aliphatics, aromatics, isoprenes, and monoterpenes .…”

“…This site is close to major traffic arteries with high traffic volumes, commercial properties, and residential areas, making it representative of a typical urban environment. 28 The Nitrate-CI-APi-TOF (Aerodyne Research Inc., USA, and Tofwerk AG, Switzerland) was deployed to detect the OOMs. 14 The calibration of OOMs is based on the calibration coefficients of sulfuric acid after mass transmission correction, which is the preferred method in the current study of OOMs.…”

Emission Characteristics, Environmental Impacts, and Health Risks of Volatile Organic Compounds from Asphalt Materials: A State-of-the-Art Review

“…Experiments reveal how reactive VOCs undergo photo-oxidation, oligomerization, and other chemical reactions in the atmosphere to form lower volatility products down to nano/micrometer particle sizes. 98 Concentrations of organic carbon in PM 2.5 correlate strongly with nearby traffic levels and corresponding vehicle/pavementrelated VOCs. 99 Source-oriented receptor models apportion 11−30% of summertime organic aerosol mass concentrations in urban locations to asphalt contributions, emphasizing their importance relative to other sources.…”