A global perspective on aerosol from low-volatility organic compounds

Abstract. Global production of organic aerosol from primary emissions of semivolatile (SVOCs) and intermediate (IVOCs) volatility organic compounds is estimated using the global chemical transport model, GEOS-Chem. SVOC oxidation is predicted to be a larger global source of net aerosol production than oxidation of traditional parent hydrocarbons (terpenes, isoprene, and aromatics). Using a prescribed rate constant and reduction in volatility for atmospheric oxidation, the yield of aerosol from SVOCs is predicted to be about 75% on a global, annually-averaged basis. For IVOCs, the use of a naphthalene-like surrogate with different high-NOx and low-NOx parameterizations produces a global aerosol yield of about 30%, or roughly 5 Tg/yr of aerosol. Estimates of the total global organic aerosol source presented here range between 60 and 100 Tg/yr. This range reflects uncertainty in the parameters for SVOC volatility, SVOC oxidation, SVOC emissions, and IVOC emissions, as well as wet deposition. The highest estimates result if SVOC emissions are significantly underestimated (by more than a factor of 2) or if wet deposition of the gas-phase semivolatile species is less effective than previous estimates. A significant increase in SVOC emissions, a reduction of the volatility of the SVOC emissions, or an increase in the enthalpy of vaporization of the organic aerosol all lead to an appreciable reduction of prediction/measurement discrepancy. In addition, if current primary organic aerosol (POA) inventories capture only about one-half of the SVOC emission and the Henrys Law coefficient for oxidized semivolatiles is on the order of 103 M/atm, a global estimate of OA production is not inconsistent with the top-down estimate of 140 Tg/yr by (Goldstein and Galbally, 2007). Additional information is needed to constrain the emissions and treatment of SVOCs and IVOCs, which have traditionally not been included in models.

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A global perspective on aerosol from low-volatility organic compounds

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-4079-2010 ◽

2010 ◽

Vol 10 (2) ◽

pp. 4079-4141 ◽

Cited By ~ 2

Author(s):

H. O. T. Pye ◽

J. H. Seinfeld

Keyword(s):

Wet Deposition ◽

Transport Model ◽

Organic Aerosol ◽

Global Perspective ◽

Chemical Transport Model ◽

Aerosol Model ◽

Global Estimate ◽

Additional Information ◽

The Us ◽

Aerosol Source

Abstract. Organic aerosol from primary semivolatile and intermediate volatility compounds is estimated using a global chemical transport model. Semivolatile organic compound (SVOC, saturation concentrations between about 0.1 and 104 μg/m3) oxidation is predicted to be a much larger global source of net aerosol production than oxidation of traditional parent hydrocarbons (terpenes, isoprene, and aromatics). Using a prescribed rate constant and reduction in volatility, the yield of aerosol (defined as the net mass of aerosol formed divided by the total mass of the parent hydrocarbon emitted) from SVOCs is predicted to be about 75% on a global, annually averaged basis. Intermediate volatility compound (IVOC, saturation concentrations between about 104 and 106 μg/m3) emissions and oxidation are highly uncertain since they are not typically measured. The use of a naphthalene-like surrogate with different high-NOx and low-NOx parameterizations produces an aerosol yield of about 30% or roughly 5 Tg/yr of aerosol from IVOC oxidation on a global basis. Estimates of the total global organic aerosol source presented here range between 60 and 100 Tg/yr. This range reflects uncertainty in the parameters for SVOC volatility, SVOC oxidation, SVOC emissions, and IVOC emissions, as well as wet deposition. The highest estimates result if SVOC emissions are significantly underestimated (by more than a factor of 2) or if wet deposition of the gas-phase semivolatile species is less effective than previous estimates. Compared to a traditional non-volatile primary organic aerosol model without IVOCs, the global estimate of organic aerosol production is at most roughly 10% higher than previous studies. Additional information is needed to constrain the emissions and treatment of SVOCs and IVOCs, which have traditionally not been included in models. Comparisons to winter organic carbon observations over the US indicate that SVOC emissions are significantly underestimated by the traditional POA inventories. The degree to which IVOC emissions or other parameters are uncertain is unknown.

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On the implications of aerosol liquid water and phase separation for organic aerosol mass

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-343-2017 ◽

2017 ◽

Vol 17 (1) ◽

pp. 343-369 ◽

Cited By ~ 65

Author(s):

Havala O. T. Pye ◽

Benjamin N. Murphy ◽

Lu Xu ◽

Nga L. Ng ◽

Annmarie G. Carlton ◽

...

Keyword(s):

Organic Carbon ◽

Organic Compounds ◽

Water Uptake ◽

Liquid Water ◽

Transport Model ◽

Organic Aerosol ◽

Water Soluble ◽

Organic Nitrates ◽

Monitoring Networks ◽

Chemical Transport Model

Abstract. Organic compounds and liquid water are major aerosol constituents in the southeast United States (SE US). Water associated with inorganic constituents (inorganic water) can contribute to the partitioning medium for organic aerosol when relative humidities or organic matter to organic carbon (OM ∕ OC) ratios are high such that separation relative humidities (SRH) are below the ambient relative humidity (RH). As OM ∕ OC ratios in the SE US are often between 1.8 and 2.2, organic aerosol experiences both mixing with inorganic water and separation from it. Regional chemical transport model simulations including inorganic water (but excluding water uptake by organic compounds) in the partitioning medium for secondary organic aerosol (SOA) when RH  >  SRH led to increased SOA concentrations, particularly at night. Water uptake to the organic phase resulted in even greater SOA concentrations as a result of a positive feedback in which water uptake increased SOA, which further increased aerosol water and organic aerosol. Aerosol properties, such as the OM ∕ OC and hygroscopicity parameter (κorg), were captured well by the model compared with measurements during the Southern Oxidant and Aerosol Study (SOAS) 2013. Organic nitrates from monoterpene oxidation were predicted to be the least water-soluble semivolatile species in the model, but most biogenically derived semivolatile species in the Community Multiscale Air Quality (CMAQ) model were highly water soluble and expected to contribute to water-soluble organic carbon (WSOC). Organic aerosol and SOA precursors were abundant at night, but additional improvements in daytime organic aerosol are needed to close the model–measurement gap. When taking into account deviations from ideality, including both inorganic (when RH  >  SRH) and organic water in the organic partitioning medium reduced the mean bias in SOA for routine monitoring networks and improved model performance compared to observations from SOAS. Property updates from this work will be released in CMAQ v5.2.

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Study of Secondary Organic Aerosol Formation from Chlorine Radical-Initiated Oxidation of Volatile Organic Compounds in a Polluted Atmosphere Using a 3D Chemical Transport Model

Environmental Science & Technology ◽

10.1021/acs.est.0c02958 ◽

2020 ◽

Vol 54 (21) ◽

pp. 13409-13418

Author(s):

Min Su Choi ◽

Xionghui Qiu ◽

Jie Zhang ◽

Shuxiao Wang ◽

Xinghua Li ◽

...

Keyword(s):

Volatile Organic Compounds ◽

Organic Compounds ◽

Secondary Organic Aerosol ◽

Transport Model ◽

Chemical Transport ◽

Organic Aerosol ◽

Aerosol Formation ◽

Chemical Transport Model ◽

Polluted Atmosphere ◽

Volatile Organic

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Modelling of organic aerosols over Europe (2002–2007) using a volatility basis set (VBS) framework: application of different assumptions regarding the formation of secondary organic aerosol

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-8499-2012 ◽

2012 ◽

Vol 12 (18) ◽

pp. 8499-8527 ◽

Cited By ~ 126

Author(s):

R. Bergström ◽

H. A. C. Denier van der Gon ◽

A. S. H. Prévôt ◽

K. E. Yttri ◽

D. Simpson

Keyword(s):

Secondary Organic Aerosol ◽

Transport Model ◽

Organic Aerosol ◽

Basis Set ◽

Emission Inventories ◽

Chemical Transport Model ◽

Wood Combustion ◽

Fire Emissions ◽

Model Studies ◽

Primary Emissions

Abstract. A new organic aerosol module has been implemented into the EMEP chemical transport model. Four different volatility basis set (VBS) schemes have been tested in long-term simulations for Europe, covering the six years 2002–2007. Different assumptions regarding partitioning of primary organic aerosol and aging of primary semi-volatile and intermediate volatility organic carbon (S/IVOC) species and secondary organic aerosol (SOA) have been explored. Model results are compared to filter measurements, aerosol mass spectrometry (AMS) data and source apportionment studies, as well as to other model studies. The present study indicates that many different sources contribute significantly to organic aerosol in Europe. Biogenic and anthropogenic SOA, residential wood combustion and vegetation fire emissions may all contribute more than 10% each over substantial parts of Europe. This study shows smaller contributions from biogenic SOA to organic aerosol in Europe than earlier work, but relatively greater anthropogenic SOA. Simple VBS based organic aerosol models can give reasonably good results for summer conditions but more observational studies are needed to constrain the VBS parameterisations and to help improve emission inventories. The volatility distribution of primary emissions is one important issue for further work. Emissions of volatile organic compounds from biogenic sources are also highly uncertain and need further validation. We can not reproduce winter levels of organic aerosol in Europe, and there are many indications that the present emission inventories substantially underestimate emissions from residential wood combustion in large parts of Europe.

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

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-9857-2012 ◽

2012 ◽

Vol 12 (4) ◽

pp. 9857-9901 ◽

Cited By ~ 1

Author(s):

B. N. Murphy ◽

N. M. Donahue ◽

C. Fountoukis ◽

M. Dall'Osto ◽

C. O'Dowd ◽

...

Keyword(s):

Organic Compounds ◽

Aqueous Phase ◽

Transport Model ◽

Field Studies ◽

Organic Aerosol ◽

Basis Set ◽

Base Case ◽

Chemical Transport Model ◽

Heterogeneous Oxidation ◽

Phase Chemistry

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 (EUCAARI) 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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Modelling of organic aerosols over Europe (2002–2007) using a volatility basis set (VBS) framework with application of different assumptions regarding the formation of secondary organic aerosol

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-5425-2012 ◽

2012 ◽

Vol 12 (2) ◽

pp. 5425-5485 ◽

Cited By ~ 9

Author(s):

R. Bergström ◽

H. A. C. Denier van der Gon ◽

A. S. H. Prévôt ◽

K. E. Yttri ◽

D. Simpson

Keyword(s):

Observational Studies ◽

Transport Model ◽

Organic Aerosol ◽

Basis Set ◽

Emission Inventories ◽

Chemical Transport Model ◽

Model Studies ◽

Primary Emissions ◽

Different Sources

Abstract. A new organic aerosol (OA) module has been implemented into the EMEP chemical transport model. Four different volatility basis set (VBS) schemes have been tested in long-term simulations for Europe, covering the six years 2002–2007. Different assumptions regarding partitioning of primary OA (POA) and aging of POA and secondary OA (SOA), have been explored. Model results are compared to filter measurements, AMS-data and source-apportionment studies, as well as to other model studies. The present study indicates that many different sources contribute significantly to OA in Europe. Fossil POA and oxidised POA, biogenic and anthropogenic SOA (BSOA and ASOA), residential burning of biomass fuels and wildfire emissions may all contribute more than 10% each over substantial parts of Europe. Simple VBS based OA models can give reasonably good results for summer OA but more observational studies are needed to constrain the VBS parameterisations and to help improve emission inventories. The volatility distribution of primary emissions is an important issue for further work. This study shows smaller contributions from BSOA to OA in Europe than earlier work, but relatively greater ASOA. BVOC emissions are highly uncertain and need further validation. We can not reproduce winter levels of OA in Europe, and there are many indications that the present emission inventories substantially underestimate emissions from residential wood burning in large parts of Europe.

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Inconsistency of ammonium–sulfate aerosol ratios with thermodynamic models in the eastern US: a possible role of organic aerosol

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-5107-2017 ◽

2017 ◽

Vol 17 (8) ◽

pp. 5107-5118 ◽

Cited By ~ 33

Author(s):

Rachel F. Silvern ◽

Daniel J. Jacob ◽

Patrick S. Kim ◽

Eloise A. Marais ◽

Jay R. Turner ◽

...

Keyword(s):

Gas Phase ◽

Ammonium Sulfate ◽

Wet Deposition ◽

Transport Model ◽

Organic Aerosol ◽

Sulfate Aerosol ◽

Chemical Transport Model ◽

Thermodynamic Models ◽

So2 Emissions ◽

Mass Transfer Limitation

Abstract. Thermodynamic models predict that sulfate aerosol (S(VI) ≡ H2SO4(aq) + HSO4−+ SO42−) should take up available ammonia (NH3) quantitatively as ammonium (NH4+) until the ammonium sulfate stoichiometry (NH4)2SO4 is close to being reached. This uptake of ammonia has important implications for aerosol mass, hygroscopicity, and acidity. When ammonia is in excess, the ammonium–sulfate aerosol ratio R =  [NH4+] ∕ [S(VI)] should approach 2, with excess ammonia remaining in the gas phase. When ammonia is in deficit, it should be fully taken up by the aerosol as ammonium and no significant ammonia should remain in the gas phase. Here we report that sulfate aerosol in the eastern US in summer has a low ammonium–sulfate ratio despite excess ammonia, and we show that this is at odds with thermodynamic models. The ammonium–sulfate ratio averages only 1.04 ± 0.21 mol mol−1 in the Southeast, even though ammonia is in large excess, as shown by the ammonium–sulfate ratio in wet deposition and by the presence of gas-phase ammonia. It further appears that the ammonium–sulfate aerosol ratio is insensitive to the supply of ammonia, remaining low even as the wet deposition ratio exceeds 6 mol mol−1. While the ammonium–sulfate ratio in wet deposition has increased by 5.8 % yr−1 from 2003 to 2013 in the Southeast, consistent with SO2 emission controls, the ammonium–sulfate aerosol ratio decreased by 1.4–3.0 % yr−1. Thus, the aerosol is becoming more acidic even as SO2 emissions decrease and ammonia emissions stay constant; this is incompatible with simple sulfate–ammonium thermodynamics. A tentative explanation is that sulfate particles are increasingly coated by organic material, retarding the uptake of ammonia. Indeed, the ratio of organic aerosol (OA) to sulfate in the Southeast increased from 1.1 to 2.4 g g−1 over the 2003–2013 period as sulfate decreased. We implement a simple kinetic mass transfer limitation for ammonia uptake to sulfate aerosols in the GEOS-Chem chemical transport model and find that we can reproduce both the observed ammonium–sulfate aerosol ratios and the concurrent presence of gas-phase ammonia. If sulfate aerosol becomes more acidic as OA ∕ sulfate ratios increase, then controlling SO2 emissions to decrease sulfate aerosol will not have the co-benefit of suppressing acid-catalyzed secondary organic aerosol (SOA) formation.

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Incomplete sulfate aerosol neutralization despite excess ammonia in the eastern US: a possible role of organic aerosol

10.5194/acp-2016-315 ◽

2016 ◽

Cited By ~ 3

Author(s):

Rachel F. Silvern ◽

Daniel J. Jacob ◽

Patrick S. Kim ◽

Eloise A. Marais ◽

Jay R. Turner

Keyword(s):

Wet Deposition ◽

Transport Model ◽

Organic Aerosol ◽

Sulfate Aerosol ◽

Chemical Transport Model ◽

So2 Emissions ◽

Mass Transfer Limitation ◽

Aerosol Mass ◽

Aircraft Observations ◽

Southeast Us

Abstract. Acid-base neutralization of sulfate aerosol (S(VI) ≡ H2SO4(aq) + HSO4− + SO42−) by ammonia (NH3) has important implications for aerosol mass, hygroscopicity, and acidity. Surface network and aircraft observations across the eastern US show that sulfate aerosol is not fully neutralized even in the presence of excess ammonia, at odds with thermodynamic equilibrium models. The sulfate aerosol neutralization ratio (f = [NH4+]/2[S(VI)]) averages only 0.51 ± 0.11 mol mol−1 at sites in the Southeast and 0.78 ± 0.13 mol mol−1 in the Northeast in summer 2013, even though ammonia is in large excess as shown by the corresponding [NH4+]/2[S(VI)] ratio in wet deposition fluxes. There is in fact no site-to-site correlation between the two quantities; the aerosol neutralization ratio in the Southeast remains in a range 0.3–0.6 mol mol−1 even as the wet deposition neutralization ratio exceeds 3 mol mol−1. While the wet deposition neutralization ratio has increased by 4.6 % a−1 from 2003 to 2013 in the Southeast US, consistent with SO2 emission controls, the aerosol neutralization ratio has decreased by 1.0–3.2 % a−1. Thus the aerosol is becoming more acidic even as SO2 emissions decrease. One possible explanation is that sulfate particles are increasingly coated by organic material, retarding the uptake of ammonia. The ratio of organic aerosol (OA) to sulfate increases over the 2003–2013 period as sulfate decreases. We implement a kinetic mass transfer limitation for ammonia uptake to sulfate aerosols in the GEOS-Chem chemical transport model and find improved agreement with surface and aircraft observations of the aerosol neutralization ratio. If sulfate aerosol becomes more acidic as OA/sulfate ratios increase, then controlling SO2 emissions to decrease sulfate aerosol will not have the co-benefit of suppressing acid-catalyzed secondary organic aerosol (SOA) formation.

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

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-10797-2012 ◽

2012 ◽

Vol 12 (22) ◽

pp. 10797-10816 ◽

Cited By ~ 64

Author(s):

B. N. Murphy ◽

N. M. Donahue ◽

C. Fountoukis ◽

M. Dall'Osto ◽

C. O'Dowd ◽

...

Keyword(s):

Organic Compounds ◽

Aqueous Phase ◽

Transport Model ◽

Field Studies ◽

Organic Aerosol ◽

Basis Set ◽

Base Case ◽

Chemical Transport Model ◽

Heterogeneous Oxidation ◽

Phase Chemistry

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Towards a satellite – in situ hybrid estimate for organic aerosol abundance

10.5194/acp-2018-651 ◽

2018 ◽

Author(s):

Jin Liao ◽

Thomas F. Hanisco ◽

Glenn M. Wolfe ◽

Jason St. Clair ◽

Jose L. Jimenez ◽

...

Keyword(s):

Transport Model ◽

Organic Aerosol ◽

Anthropogenic Sources ◽

Spatiotemporal Variability ◽

Chemical Transport Model ◽

Ozone Monitoring Instrument ◽

Near Surface ◽

Using Data ◽

Primary Emissions

Abstract. Organic aerosol (OA) is one of the main components of the global particulate burden and intimately links natural and anthropogenic emissions with air quality and climate. It is challenging to accurately represent OA in global models. Direct quantification of global OA abundance is not possible with current remote sensing technology; however, it may be possible to exploit correlations of OA with remotely observable quantities to infer OA spatiotemporal variability. In particular, formaldehyde (HCHO) and OA share common sources via both primary emissions and secondary production from oxidation of volatile organic compounds (VOCs). We examine OA-HCHO correlations using data from summer-time airborne campaigns investigating biogenic (NASA SEAC4RS and DC3), biomass burning (NASA SEAC4RS) and anthropogenic conditions (NOAA CalNex and NASA KORUS-AQ). In situ OA correlates well with HCHO (r = 0.59–0.97) but the slope and intercept of this relationship vary with chemical regime. For biogenic and anthropogenic regions, the OA-vs-HCHO slope is higher in low NOx conditions, where HCHO yields are lower and aerosol yields are likely higher. The OA-vs-HCHO slope of wild fires is more than 9 times higher than that associated with biogenic and anthropogenic sources. An estimate of near-surface OA is derived by combining observed in situ relationships with HCHO column retrievals from NASA’s Ozone Monitoring Instrument (OMI). We evaluate this OA estimate against OA observations from the US EPA IMPROVE network and simulated OA from the GEOS-Chem global chemical transport model. The OA estimate compares well with IMPROVE data obtained over summer months (e.g. slope = 0.62, r = 0.56 for August 2013), comparable to intensively validated GEOS-Chem performance (e.g. slope = 0.57, r = 0.56) and superior to the correlation with satellite-derived total aerosol extinction (r = 0.41). Improving the detection limit of satellite HCHO and expanding in situ airborne HCHO and OA coverage in future missions will improve the quality and spatiotemporal coverage of this OA estimate, potentially enabling constraints on the global OA distribution.

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