Formation of highly oxygenated organic aerosol in the atmosphere: Insights from the Finokalia Aerosol Measurement Experiments

Hildebrandt, L.; Kostenidou, Evangelia; Mihalopoulos, N.; Worsnop, Douglas R.; Donahue, Neil M.; Pandis, Spyros Ν.

doi:10.1029/2010gl045193

Cited by 50 publications

(57 citation statements)

References 32 publications

(43 reference statements)

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“…1B this could partly counteract the mass increases of aging, though the average concentrations would still be elevated and variable. Furthermore, the residual aerosol would be highly oxidized and distributed down to very low volatility, consistent with observations in remote locations (15,43).…”

Section: Resultssupporting

confidence: 57%

Aging of biogenic secondary organic aerosol via gas-phase OH radical reactions

Donahue

Henry

Mentel

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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The Multiple Chamber Aerosol Chemical Aging Study (MUCHA-CHAS) tested the hypothesis that hydroxyl radical (OH) aging significantly increases the concentration of first-generation biogenic secondary organic aerosol (SOA). OH is the dominant atmospheric oxidant, and MUCHACHAS employed environmental chambers of very different designs, using multiple OH sources to explore a range of chemical conditions and potential sources of systematic error. We isolated the effect of OH aging, confirming our hypothesis while observing corresponding changes in SOA properties. The mass increases are consistent with an existing gap between global SOA sources and those predicted in models, and can be described by a mechanism suitable for implementation in those models.atmospheric chemistry | biosphere-atmosphere interactions O rganic aerosol (OA) comprises a large fraction of fine-particle mass (PM 2.5 ) (1). In the developed world, 1-2% of deaths are blamed on inhalation of PM 2.5 (2), and the leading uncertainty in climate forcing is the interplay between the number of fine particles large enough to nucleate cloud droplets and the amount of sunlight reflected by those clouds (3). Oxidation and condensation of organics play a major but uncertain role in both phenomena.Traditional models treat most OA as nonvolatile primary OA (POA), augmented by secondary OA (SOA) (4), and they underpredict OA concentrations by a factor of 3-10 (5). α-Pinene is a major biogenic SOA source, sometimes used to represent all SOA in global models (4, 6). However, less than 20% of the carbon from fresh α-pinene oxidation condenses in chambers at room temperature; (7) the remainder is gaseous (Fig. 1A). This "chamber" SOA is modestly oxidized, with an oxygen to carbon ratio ðO∶CÞ < 0.4 (7). It is unambiguously semivolatile: Yields rise with increasing SOA mass loading (8, 9) and decreasing temperature (10), and the SOA evaporates upon heating (11-13) and after isothermal dilution (14).In contrast, ambient OA is highly oxidized (0.5 ≤ O∶C ≤ 1.0) (1, 15) and not very volatile (16). Ambient SOA is much less volatile than ambient POA (16). Consequently, "chamber" SOA does not represent the atmosphere. Our hypothesis is that homogeneous gas-phase aging by OH is a major missing process connecting chamber studies to the atmosphere. Considerable attention has been paid to heterogeneous uptake of oxidants to particles (17, 18), and recently gas-phase oxidation of semivolatile primary emissions (19), but the degree to which gas-phase oxidation can age chamber SOA is uncertain (1,4,18,20).OA resides in the atmosphere for about one week (21), while the gas-phase lifetimes of major semivolatile SOA constituents are far shorter. Typical α-pinene products pinonaldehyde, cispinonic acid, and pinic acid all have lifetimes of only a few hours for summertime conditions (22). Without question, oxidation of semivolatile SOA vapors will perturb the equilibrium phase partitioning of these constituents. Because almost all of the first-generation products are less volatile than α...

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Section: Resultssupporting

confidence: 57%

Aging of biogenic secondary organic aerosol via gas-phase OH radical reactions

Donahue

Henry

Mentel

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

269

303

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“…Using the organic mass at m/z 44 as measured by the Q-AMS, they estimated O:C with the parameterization of Aiken et al (2008). The contribution from m/z 57 (characteristic of fresh, hydrocarbon-like organic species) was barely detectable throughout the campaign, indicating that heavily Hildebrandt et al (2010b). That study also found the OA chemical composition to be much more variable in the winter than the summer and concluded that decreases in photochemical activity in the wintertime likely explain the discrepancy.…”

Section: Measurementsmentioning

confidence: 99%

Functionalization and fragmentation during ambient organic aerosol aging: application of the 2-D volatility basis set to field studies

et al. 2012

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Abstract. Multigenerational oxidation chemistry of atmospheric organic compounds and its effects on aerosol loadings and chemical composition is investigated by implementing the Two-Dimensional Volatility Basis Set (2-D-VBS) in a Lagrangian host chemical transport model. Three model formulations were chosen to explore the complex interactions between functionalization and fragmentation processes during gas-phase oxidation of organic compounds by the hydroxyl radical. The base case model employs a conservative transformation by assuming a reduction of one order of magnitude in effective saturation concentration and an increase of oxygen content by one or two oxygen atoms per oxidation generation. A second scheme simulates functionalization in more detail using group contribution theory to estimate the effects of oxygen addition to the carbon backbone on the compound volatility. Finally, a fragmentation scheme is added to the detailed functionalization scheme to create a functionalization-fragmentation parameterization. Two condensed-phase chemistry pathways are also implemented as additional sensitivity tests to simulate (1) heterogeneous oxidation via OH uptake to the particle-phase and (2) aqueous-phase chemistry of glyoxal and methylglyoxal.The model is applied to summer and winter periods at three sites where observations of organic aerosol (OA) mass and O:C were obtained during the European Integrated Project on Aerosol Cloud Climate and Air Quality Interactions (EU-CAARI) campaigns. The base case model reproduces observed mass concentrations and O:C well, with fractional errors (FE) lower than 55 % and 25 %, respectively. The detailed functionalization scheme tends to overpredict OA concentrations, especially in the summertime, and also underpredicts O:C by approximately a factor of 2. The detailed functionalization model with fragmentation agrees well with the observations for OA concentration, but still underpredicts O:C. Both heterogeneous oxidation and aqueous-phase processing have small effects on OA levels but heterogeneous oxidation, as implemented here, does enhance O:C by about 0.1. The different schemes result in very different fractional attribution for OA between anthropogenic and biogenic sources.

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“…Nevertheless, the absence of HO2 measurements during MINOS impairs our ability to directly compare the OH chemistry from the two datasets for a regional perspective. However, the peak OH levels observed during CYPHEX are comparable to the midday OH concentrations predicted for the Finokalia Aerosol Measurement Experiments (FAME-08) at a remote coastal site on the island of Crete, Greece (Hildebrandt et al, 2010). The FAME measurements showed the presence of aged, highly 10 oxygenated organic aerosols (OA) during summer compared to winter despite being heavily influenced by continental air mases (53 %) during summer and aged marine air masses (61 %) during winter.…”

Section: Hox Measurements During Cyphex and Associated Meteorologicalmentioning

confidence: 60%

Section: Hox Measurements During Cyphex and Associated Meteorologicalmentioning

confidence: 99%

“…The FAME measurements showed the presence of aged, highly 10 oxygenated organic aerosols (OA) during summer compared to winter despite being heavily influenced by continental air mases (53 %) during summer and aged marine air masses (61 %) during winter. The presence of highly oxygenated OA during summer were attributed to strong photochemical impacts due to higher O3 and UV and levels during summer, leading to double the values of midday OH concentrations during summer compared to winter (Hildebrandt et al, 2010).While OH measurements during CYPHEX started on 12 July, 2014 (day number: 193), systematic HO2 measurements 15 started much later from 21 July, 2014 (day number: 202). Simultaneous measurements of OH and HO2 during CYPHEX are available for the period 21-31 July, and the discussion in this work is based on this common dataset.…”

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confidence: 99%

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Oxidation processes in the Eastern Mediterranean atmosphere: Evidence from the Modelling of HO<sub>x</sub> Measurements over Cyprus

Mallik¹,

Tomsche²,

Bourtsoukidis³

et al. 2018

Preprint

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Abstract. The Mediterranean is a climatically sensitive region located at the crossroads of air masses from three continents: 15Europe, Africa and Asia. The chemical processing of air masses over this region has implications not only for the air quality, but also for the long-range transport of air pollution. To obtain a comprehensive understanding of oxidation processes over the Mediterranean, atmospheric concentrations of the hydroxyl radical (OH) and the hydroperoxyl radical (HO2) were measured during an intensive field campaign (CYprus PHotochemistry EXperiment, CYPHEX-2014) in the north-west of Cyprus in the summer of 2014. Very low local anthropogenic and biogenic emissions around the measurement location 20 provided a vantage point to study the contrasts in atmospheric oxidation pathways under highly processed marine air masses and those influenced by relatively fresh emissions from mainland Europe.The CYPHEX measurements were used to evaluate OH and HO2 simulations using a photochemical box model (CAABA/MECCA) constrained with CYPHEX observations of O3, CO, NOx, hydrocarbons, peroxides and other major HOx (OH + HO2) sources and sinks in a low NOx environment (<100 pptv NO). The model simulations for OH showed very good 25 agreement with in-situ OH observations. Model simulations for HO2 also agreed fairly well with in-situ observations except when pinene levels exceeded 80 pptv. Different schemes to improve the agreement between observed and modelled HO2, including changing the rate coefficients for the reactions of terpene generated peroxy radicals (RO2) with NO and HO2 as well as the autoxidation of terpene generated RO2 species, are explored in this work. The main source of OH in Cyprus was its primary production from O3 photolysis during the day and HONO photolysis during early morning. Recycling contributed 30 about one-third of the total OH production, and the maximum recycling efficiency was about 70 %. CO, which was the largest OH sink was also the largest HO2 source. Lowest HOx production and losses occurred when the air masses had higher residence time over the oceans.Atmos. Chem. Phys. Discuss., https://doi.org/10. 5194/acp-2018-25 Manuscript under review for journal Atmos. Chem. Phys. Air pollution and HOx chemistryThe chemical and photochemical processing of air pollutants, in conjunction with local emissions, meteorology and atmospheric transport, strongly influences the air quality over a region. The regional air quality impacts human health, agriculture, the overall condition of the biosphere and subsequently the climate. Studies attribute 2-4 million premature 5 deaths globally to outdoor air pollution (Silva et al., 2013;Lelieveld et al., 2015). Oxidants in the Earth's atmosphere prevent the pollutants released into it from building up to toxic levels. These oxidants not only convert many toxic pollutants into less toxic forms (e.g. CO to CO2) but also help in their removal (e.g. NOx and SO2 are converted into soluble HNO3 and H2SO4 respectively), although some toxic chemicals may s...

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Formation of highly oxygenated organic aerosol in the atmosphere: Insights from the Finokalia Aerosol Measurement Experiments

Cited by 50 publications

References 32 publications

Aging of biogenic secondary organic aerosol via gas-phase OH radical reactions

Aging of biogenic secondary organic aerosol via gas-phase OH radical reactions

Functionalization and fragmentation during ambient organic aerosol aging: application of the 2-D volatility basis set to field studies

Oxidation processes in the Eastern Mediterranean atmosphere: Evidence from the Modelling of HO<sub>x</sub> Measurements over Cyprus

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Formation of highly oxygenated organic aerosol in the atmosphere: Insights from the Finokalia Aerosol Measurement Experiments

Cited by 50 publications

References 32 publications

Aging of biogenic secondary organic aerosol via gas-phase OH radical reactions

Aging of biogenic secondary organic aerosol via gas-phase OH radical reactions

Functionalization and fragmentation during ambient organic aerosol aging: application of the 2-D volatility basis set to field studies

Oxidation processes in the Eastern Mediterranean atmosphere: Evidence from the Modelling of HO&lt;sub&gt;x&lt;/sub&gt; Measurements over Cyprus

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Oxidation processes in the Eastern Mediterranean atmosphere: Evidence from the Modelling of HO<sub>x</sub> Measurements over Cyprus