Chemical evolution of atmospheric organic carbon over multiple generations of oxidation

Isaacman‐VanWertz, Gabriel; Massoli, P.; O’Brien, Rachel E.; Lim, Christopher Y.; Franklin, J. P.; Moss, J. A.; Hunter, J. F.; Nowak, John B.; Canagaratna, Manjula R.; Misztal, Pawel K.; Arata, Caleb; Roscioli, Joseph R.; Herndon, Scott T.; Onasch, T. B.; Lambe, Andrew T.; Jayne, John T.; Su, L.; Knopf, D. A.; Goldstein, Allen H.; Worsnop, Douglas R.; Kroll, J. H.

doi:10.1038/s41557-018-0002-2

Cited by 114 publications

(166 citation statements)

References 70 publications

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“…We notice that the OPOA spectrum is dominated by C x H y + (58%, and 69–76% in FFOA), while that of OOA mainly comprises of C x H y O z + (67–69%), in fact mainly CO 2 + and CO + , two ions dominantly from fragmentation of organic acids (Canagaratna et al, ). Therefore, the oxidation of POA appears to play an important role in the formation of OPOA, while fragmentation to form low‐volatility products could be more important for photochemical aging of OOA (Isaacman‐VanWertz et al, ).…”

Section: Resultsmentioning

confidence: 99%

Changes in Aerosol Chemistry From 2014 to 2016 in Winter in Beijing: Insights From High‐Resolution Aerosol Mass Spectrometry

et al. 2019

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Air quality has been continuously improved in recent years in Beijing, yet severe haze episodes still frequently occur in winter. Here we deployed an Aerodyne high‐resolution aerosol mass spectrometer in two winter seasons during the same period to investigate the changes in aerosol chemistry from 2014 to 2016 in Beijing. Compared to 2014, submicron aerosol (PM1) species showed ubiquitous increases in mass concentrations by 10–130% in winter 2016, of which nitrate showed the largest increase among all aerosol species leading to a much higher NO3/SO4 ratio in 2016 (1.36 ± 0.90) than 2014 (0.72 ± 0.59). This result highlights an increasing role of nitrate in particulate matter pollution in recent years in Beijing. Aerosol composition and size distributions also changed significantly. Secondary inorganic species showed elevated contributions by ~10% in winter 2016 associated with corresponding decreases in organic aerosol (OA). Positive matrix factorization of OA illustrated the significant changes in both primary emissions and secondary production. While cooking OA decreased substantially from 25% in 2014 to 15% in 2016, the contribution of biomass burning OA slightly increased instead. Although secondary OA contributed similarly to OA in the two winters (49% vs. 53%), we observed ubiquitous increases (~50%) in photochemically related oxygenated OA and oxidized primary OA, and oxygen‐to‐carbon ratios of OA, indicating the enhanced photochemical production in winter 2016. Aqueous‐phase production of secondary OA however was relatively similar in the two winters. Further analysis demonstrated that the changes in aerosol and OA composition varied differently across different pollution and relative humidity levels.

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Section: Resultsmentioning

confidence: 99%

Changes in Aerosol Chemistry From 2014 to 2016 in Winter in Beijing: Insights From High‐Resolution Aerosol Mass Spectrometry

et al. 2019

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“…Although the oxidation of BVOCs has been widely studied, it has mostly been constrained to the early stages (first-and second-generation intermediates), and many uncertainties still exist (Johnson and Marston, 2008;Isaacman-VanWertz et al, 2018;Atkinson and Arey, 2003). The first step of ozonolysis for the three BVOCs (α-pinene, 3 -carene, and X.…”

Section: Possible Formation Pathways Of Water-relevant C 10 and C 20 mentioning

confidence: 99%

Relative humidity effect on the formation of highly oxidized molecules and new particles during monoterpene oxidation

Li¹,

Hao²,

Abbatt³

et al. 2019

Atmos. Chem. Phys.

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Abstract. It has been widely observed around the world that the frequency and intensity of new particle formation (NPF) events are reduced during periods of high relative humidity (RH). The current study focuses on how RH affects the formation of highly oxidized molecules (HOMs), which are key components of NPF and initial growth caused by oxidized organics. The ozonolysis of α-pinene, limonene, and Δ3-carene, with and without OH scavengers, were carried out under low NOx conditions under a range of RH (from ∼3 % to ∼92 %) in a temperature-controlled flow tube to generate secondary organic aerosol (SOA). A Scanning Mobility Particle Sizer (SMPS) was used to measure the size distribution of generated particles, and a novel transverse ionization chemical ionization inlet with a high-resolution time-of-fight mass spectrometer detected HOMs. A major finding from this work is that neither the detected HOMs nor their abundance changed significantly with RH, which indicates that the detected HOMs must be formed from water-independent pathways. In fact, the distinguished OH- and O3-derived peroxy radicals (RO2), HOM monomers, and HOM dimers could mostly be explained by the autoxidation of RO2 followed by bimolecular reactions with other RO2 or hydroperoxy radicals (HO2), rather than from a water-influenced pathway like through the formation of a stabilized Criegee intermediate (sCI). However, as RH increased from ∼3 % to ∼92 %, the total SOA number concentrations decreased by a factor of 2–3 while SOA mass concentrations remained relatively constant. These observations show that, while high RH appears to inhibit NPF as evident by the decreasing number concentration, this reduction is not caused by a decrease in RO2-derived HOM formation. Possible explanations for these phenomena were discussed.

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“…Henry's law solubility constants (H values; required for calculating dry deposition resistances, gas-phase wet deposition, and air-sea fluxes) are computed following Travis et al (2016) and Nguyen et al (2015) for nitric acid, hydrogen peroxide, and a suite of isoprene-derived oxygenated VOCs (isoprene hydroxy hydroperoxides, isoprene hydroxynitrate, isoprene epoxides, MVK/MACR nitrates, propanone nitrate, glycolaldehyde, hydroxyacetone). Values for lumped ≥ C4 alkylnitrates and formaldehyde are based on Marais et al (2016) and Jacob (2000), respectively, while those for benzene, toluene, and xylene (representing lumped C8 aromatics) are taken from Staudinger and Roberts (2001). The lumped xylene species in the model uses the mean H value from the corresponding individual C8 compounds (o-xylene, m-xylene, p-xylene, ethylbenzene).…”

Section: Chen Et Al: Sources and Sinks Of Atmospheric Vocsmentioning

confidence: 99%

On the sources and sinks of atmospheric VOCs: an integrated analysis of recent aircraft campaigns over North America

et al. 2019

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Abstract. We apply a high-resolution chemical transport model (GEOS-Chem CTM) with updated treatment of volatile organic compounds (VOCs) and a comprehensive suite of airborne datasets over North America to (i) characterize the VOC budget and (ii) test the ability of current models to capture the distribution and reactivity of atmospheric VOCs over this region. Biogenic emissions dominate the North American VOC budget in the model, accounting for 70 % and 95 % of annually emitted VOC carbon and reactivity, respectively. Based on current inventories anthropogenic emissions have declined to the point where biogenic emissions are the dominant summertime source of VOC reactivity even in most major North American cities. Methane oxidation is a 2× larger source of nonmethane VOCs (via production of formaldehyde and methyl hydroperoxide) over North America in the model than are anthropogenic emissions. However, anthropogenic VOCs account for over half of the ambient VOC loading over the majority of the region owing to their longer aggregate lifetime. Fires can be a significant VOC source episodically but are small on average. In the planetary boundary layer (PBL), the model exhibits skill in capturing observed variability in total VOC abundance (R2=0.36) and reactivity (R2=0.54). The same is not true in the free troposphere (FT), where skill is low and there is a persistent low model bias (∼ 60 %), with most (27 of 34) model VOCs underestimated by more than a factor of 2. A comparison of PBL : FT concentration ratios over the southeastern US points to a misrepresentation of PBL ventilation as a contributor to these model FT biases. We also find that a relatively small number of VOCs (acetone, methanol, ethane, acetaldehyde, formaldehyde, isoprene + oxidation products, methyl hydroperoxide) drive a large fraction of total ambient VOC reactivity and associated model biases; research to improve understanding of their budgets is thus warranted. A source tracer analysis suggests a current overestimate of biogenic sources for hydroxyacetone, methyl ethyl ketone and glyoxal, an underestimate of biogenic formic acid sources, and an underestimate of peroxyacetic acid production across biogenic and anthropogenic precursors. Future work to improve model representations of vertical transport and to address the VOC biases discussed are needed to advance predictions of ozone and SOA formation.

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Chemical evolution of atmospheric organic carbon over multiple generations of oxidation

Cited by 114 publications

References 70 publications

Changes in Aerosol Chemistry From 2014 to 2016 in Winter in Beijing: Insights From High‐Resolution Aerosol Mass Spectrometry

Changes in Aerosol Chemistry From 2014 to 2016 in Winter in Beijing: Insights From High‐Resolution Aerosol Mass Spectrometry

Relative humidity effect on the formation of highly oxidized molecules and new particles during monoterpene oxidation

On the sources and sinks of atmospheric VOCs: an integrated analysis of recent aircraft campaigns over North America

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