Secondary organic aerosol in the global aerosol – chemistry transport model Oslo CTM2

Abstract. The global chemical transport model Oslo CTM2 has been extended to include the formation, transport and deposition of secondary organic aerosol (SOA). Precursor hydrocarbons which are oxidised to form condensible species include both biogenic species such as terpenes and isoprene, as well as species emitted predominantly by anthropogenic activities (toluene, m-xylene, methylbenzene and other aromatics). A model simulation for 2004 gives an annual global SOA production of approximately 55 Tg. Of this total, 2.5 Tg is found to consist of the oxidation products of anthropogenically emitted hydrocarbons, and about 15 Tg is formed by the oxidation products of isoprene. The global production of SOA is increased to about 69 Tg yr−1 by allowing semi-volatile species to partition to ammonium sulphate aerosol. This brings modelled organic aerosol values closer to those observed, however observations in Europe remain significantly underestimated. Allowing SOA to partition into ammonium sulphate aerosol increases the contribution of anthropogenic SOA from about 4.5% to 9.4% of the total production. Total modelled organic aerosol (OA) values are found to represent a lower fraction of the measured values in winter (when primary organic aerosol (POA) is the dominant OA component) than in summer, which may be an indication that estimates of POA emissions are too low. Additionally, for measurement stations where the summer OA values are higher than in winter, the model generally underestimates the increase in summertime OA. In order to correctly model the observed increase in OA in summer, additional SOA sources or formation mechanisms may be necessary. The importance of NO3 as an oxidant of SOA precursors is found to vary regionally, causing up to 50%–60% of the total amount of SOA near the surface in polluted regions and less than 25% in more remote areas, if the yield of condensible oxidation products for β-pinene is used for NO3 oxidation of all terpenes. Reducing the yield for α-pinene and limonene oxidation in line with recent measurements reduces the global fraction of SOA formed from NO3 oxidation products from 27% to about 21%. This study underscores the need for SOA to be represented in a more realistic way in global aerosol models in order to better reproduce observations of organic aerosol burdens in industrialised and biomass burning regions.

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Characterization of a real-time tracer for isoprene epoxydiols-derived secondary organic aerosol (IEPOX-SOA) from aerosol mass spectrometer measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-11807-2015 ◽

2015 ◽

Vol 15 (20) ◽

pp. 11807-11833 ◽

Cited By ~ 121

Author(s):

W. W. Hu ◽

P. Campuzano-Jost ◽

B. B. Palm ◽

D. A. Day ◽

A. M. Ortega ◽

...

Keyword(s):

Mass Spectrometer ◽

Secondary Organic Aerosol ◽

Transport Model ◽

Organic Aerosol ◽

Oxidation Products ◽

Chemical Transport Model ◽

Aerosol Mass Spectrometer ◽

Aerosol Mass ◽

Multiple Field

Abstract. Substantial amounts of secondary organic aerosol (SOA) can be formed from isoprene epoxydiols (IEPOX), which are oxidation products of isoprene mainly under low-NO conditions. Total IEPOX-SOA, which may include SOA formed from other parallel isoprene oxidation pathways, was quantified by applying positive matrix factorization (PMF) to aerosol mass spectrometer (AMS) measurements. The IEPOX-SOA fractions of organic aerosol (OA) in multiple field studies across several continents are summarized here and show consistent patterns with the concentration of gas-phase IEPOX simulated by the GEOS-Chem chemical transport model. During the Southern Oxidant and Aerosol Study (SOAS), 78 % of PMF-resolved IEPOX-SOA is accounted by the measured IEPOX-SOA molecular tracers (2-methyltetrols, C5-Triols, and IEPOX-derived organosulfate and its dimers), making it the highest level of molecular identification of an ambient SOA component to our knowledge. An enhanced signal at C5H6O+ (m/z 82) is found in PMF-resolved IEPOX-SOA spectra. To investigate the suitability of this ion as a tracer for IEPOX-SOA, we examine fC5H6O (fC5H6O= C5H6O+/OA) across multiple field, chamber, and source data sets. A background of ~ 1.7 ± 0.1 ‰ (‰ = parts per thousand) is observed in studies strongly influenced by urban, biomass-burning, and other anthropogenic primary organic aerosol (POA). Higher background values of 3.1 ± 0.6 ‰ are found in studies strongly influenced by monoterpene emissions. The average laboratory monoterpene SOA value (5.5 ± 2.0 ‰) is 4 times lower than the average for IEPOX-SOA (22 ± 7 ‰), which leaves some room to separate both contributions to OA. Locations strongly influenced by isoprene emissions under low-NO levels had higher fC5H6O (~ 6.5 ± 2.2 ‰ on average) than other sites, consistent with the expected IEPOX-SOA formation in those studies. fC5H6O in IEPOX-SOA is always elevated (12–40 ‰) but varies substantially between locations, which is shown to reflect large variations in its detailed molecular composition. The low fC5H6O (< 3 ‰) reported in non-IEPOX-derived isoprene-SOA from chamber studies indicates that this tracer ion is specifically enhanced from IEPOX-SOA, and is not a tracer for all SOA from isoprene. We introduce a graphical diagnostic to study the presence and aging of IEPOX-SOA as a triangle plot of fCO2 vs. fC5H6O. Finally, we develop a simplified method to estimate ambient IEPOX-SOA mass concentrations, which is shown to perform well compared to the full PMF method. The uncertainty of the tracer method is up to a factor of ~ 2, if the fC5H6O of the local IEPOX-SOA is not available. When only unit mass-resolution data are available, as with the aerosol chemical speciation monitor (ACSM), all methods may perform less well because of increased interferences from other ions at m/z 82. This study clarifies the strengths and limitations of the different AMS methods for detection of IEPOX-SOA and will enable improved characterization of this OA component.

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Aerosol mass spectrometer constraint on the global secondary organic aerosol budget

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-12109-2011 ◽

2011 ◽

Vol 11 (23) ◽

pp. 12109-12136 ◽

Cited By ~ 319

Author(s):

D. V. Spracklen ◽

J. L. Jimenez ◽

K. S. Carslaw ◽

D. R. Worsnop ◽

M. J. Evans ◽

...

Keyword(s):

Mass Spectrometer ◽

Secondary Organic Aerosol ◽

Transport Model ◽

Model Simulation ◽

Anthropogenic Pollution ◽

Organic Aerosol ◽

Anthropogenic Source ◽

Chemical Transport Model ◽

Aerosol Mass Spectrometer ◽

Aerosol Mass

Abstract. The budget of atmospheric secondary organic aerosol (SOA) is very uncertain, with recent estimates suggesting a global source of between 12 and 1820 Tg (SOA) a−1. We used a dataset of aerosol mass spectrometer (AMS) observations from 34 different surface locations to evaluate the GLOMAP global chemical transport model. The standard model simulation (which included SOA from monoterpenes only) underpredicted organic aerosol (OA) observed by the AMS and had little skill reproducing the variability in the dataset. We simulated SOA formation from biogenic (monoterpenes and isoprene), lumped anthropogenic and lumped biomass burning volatile organic compounds (VOCs) and varied the SOA yield from each precursor source to produce the best overall match between model and observations. We assumed that SOA is essentially non-volatile and condenses irreversibly onto existing aerosol. Our best estimate of the SOA source is 140 Tg (SOA) a−1 but with a large uncertainty range which we estimate to be 50–380 Tg (SOA) a−1. We found the minimum in normalised mean error (NME) between model and the AMS dataset when we assumed a large SOA source (100 Tg (SOA) a−1) from sources that spatially matched anthropogenic pollution (which we term antropogenically controlled SOA). We used organic carbon observations compiled by Bahadur et al. (2009) to evaluate our estimated SOA sources. We found that the model with a large anthropogenic SOA source was the most consistent with these observations, however improvement over the model with a large biogenic SOA source (250 Tg (SOA) a−1) was small. We used a dataset of 14C observations from rural locations to evaluate our estimated SOA sources. We estimated a maximum of 10 Tg (SOA) a−1 (10 %) of the anthropogenically controlled SOA source could be from fossil (urban/industrial) sources. We suggest that an additional anthropogenic source is most likely due to an anthropogenic pollution enhancement of SOA formation from biogenic VOCs. Such an anthropogenically controlled SOA source would result in substantial climate forcing. We estimated a global mean aerosol direct effect of −0.26 ± 0.15 Wm−2 and indirect (cloud albedo) effect of −0.6+0.24−0.14 Wm−2 from anthropogenically controlled SOA. The biogenic and biomass SOA sources are not well constrained with this analysis due to the limited number of OA observations in regions and periods strongly impacted by these sources. To further improve the constraints by this method, additional OA observations are needed in the tropics and the Southern Hemisphere.

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Isoprene oxidation by nitrate radical: alkyl nitrate and secondary organic aerosol yields

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-8857-2009 ◽

2009 ◽

Vol 9 (2) ◽

pp. 8857-8902 ◽

Cited By ~ 4

Author(s):

A. W. Rollins ◽

A. Kiendler-Scharr ◽

J. Fry ◽

T. Brauers ◽

S. S. Brown ◽

...

Keyword(s):

First Generation ◽

Secondary Organic Aerosol ◽

Model Simulation ◽

Effective Rate Constant ◽

Organic Aerosol ◽

Effective Rate ◽

Oxidation Products ◽

Alkyl Nitrates ◽

Alkyl Nitrate ◽

Isoprene Oxidation

Abstract. Alkyl nitrates and secondary organic aerosol (SOA) produced during the oxidation of isoprene by nitrate radicals has been observed in the SAPHIR chamber. We find the yield of nitrates is 70±8% from the isoprene+NO3 reaction, and the yield for secondary dinitrates produced in the reaction of primary isoprene nitrates with NO3 is 40±20%. We find an effective rate constant for reaction of NO3 with the group of first generation oxidation products to be 7×10−14 cm3 s−1. At the low total organic aerosol concentration in the chamber (max ≈0.6 μg m−3) we observed a mass yield (ΔSOA mass/Δisoprene mass) of 2% for the entire 16 h experiment. However a comparison of the timing of the observed SOA production to a box model simulation of first and second generation oxidation products shows that the yield from the first generation products was <0.2% while the further oxidation of the initial products leads to a yield of 10% (defined as ΔSOA/Δisoprene2x where Δisoprene2x is the mass of isoprene which reacted twice with NO3). The SOA yield of 10% is consistent with equilibrium partitioning of highly functionalized C5 products of isoprene oxidation.

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Mixing times of organic molecules within secondary organic aerosol particles: a global planetary boundary layer perspective

10.5194/acp-2017-247 ◽

2017 ◽

Cited By ~ 1

Author(s):

Adrian M. Maclean ◽

Christopher L. Butenhoff ◽

James W. Grayson ◽

Kelley Barsanti ◽

Jose L. Jimenez ◽

...

Keyword(s):

Organic Molecules ◽

Secondary Organic Aerosol ◽

Transport Model ◽

Laboratory Data ◽

Chemical Transport ◽

Organic Aerosol ◽

Mixing Times ◽

Chemical Transport Model ◽

Transport Models ◽

Lack Of Information

Abstract. When simulating the formation and life cycle of secondary organic aerosol (SOA) with chemical transport models, it is often assumed that organic molecules are well mixed within SOA particles on the time scale of 1 h. While this assumption has been debated vigorously in the literature, the issue remains unresolved in part due to a lack of information on the mixing times within SOA particles as a function of both temperature and relative humidity. Using laboratory data, meteorological fields and a chemical transport model, we determine how often mixing times are

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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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Improving the representation of secondary organic aerosol (SOA) in the MOZART-4 global chemical transport model

Geoscientific Model Development Discussions ◽

10.5194/gmdd-5-4187-2012 ◽

2012 ◽

Vol 5 (4) ◽

pp. 4187-4232 ◽

Cited By ~ 1

Author(s):

A. Mahmud ◽

K. C. Barsanti

Keyword(s):

South America ◽

Secondary Organic Aerosol ◽

Transport Model ◽

Organic Aerosol ◽

Basis Set ◽

Base Case ◽

Chemical Transport Model ◽

Annual Average ◽

Modeling Studies ◽

The Usa

Abstract. The secondary organic aerosol (SOA) module in the Model for Ozone and Related chemical Tracers, version 4 (MOZART-4) has been updated by replacing existing two-product (2p) parameters with those obtained from two-product volatility basis set (2p-VBS) fits, and by treating SOA formation from the following volatile organic compounds (VOCs): isoprene, propene and lumped alkenes. Strong seasonal and spatial variations in global SOA distributions were demonstrated, with significant differences in the predicted concentrations between the base-case and updated model versions. The base-case MOZART-4 predicted annual average SOA of 0.36 ± 0.50 μg m−3 in South America, 0.31 ± 0.38 μg m−3 in Indonesia, 0.09 ± 0.05 μg m−3 in the USA, and 0.12 ± 0.07 μg m−3 in Europe. Concentrations from the updated versions of the model showed a~marked increase in annual average SOA. Using the updated set of parameters alone (MZ4-v1) increased annual average SOA by ~8%, ~16%, ~56%, and ~108% from the base-case in South America, Indonesia, USA, and Europe, respectively. Treatment of additional parent VOCs (MZ4-v2) resulted in an even more dramatic increase of ~178–406% in annual average SOA for these regions over the base-case. The increases in predicted SOA concentrations further resulted in increases in corresponding SOA contributions to annual average total aerosol optical depth (AOD) by <1% for MZ4-v1 and ~1–6% for MZ4-v2. Estimated global SOA production was ~6.6 Tg yr−1 and ~19.1 Tg yr−1 with corresponding burdens of ~0.24 Tg and ~0.59 Tg using MZ4-v1 and MZ4-v2, respectively. The SOA budgets predicted in the current study fall well within reported ranges for similar modeling studies, 6.7 to 96 Tg yr−1, but are lower than recently reported observationally-constrained values, 50 to 380 Tg yr−1. With MZ4-v2, simulated SOA concentrations at the surface were also in reasonable agreement with comparable modeling studies and observations. Concentrations of estimated organic aerosol (OA) at the surface, however, showed under-prediction in Europe and over-prediction in the Amazonian regions and Malaysian Borneo during certain months of the year. Overall, the updated version of MOZART-4, MZ4-v2, showed consistently better skill in predicting SOA and OA levels and spatial distributions as compared with unmodified MOZART-4. The MZ4-v2 updates may be particularly important when MOZART-4 output is used to generate boundary conditions for regional air quality simulations that require more accurate representation of SOA concentrations and distributions.

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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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Evaluation of the volatility basis-set approach for the simulation of organic aerosol formation in the Mexico City metropolitan area

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-525-2010 ◽

2010 ◽

Vol 10 (2) ◽

pp. 525-546 ◽

Cited By ~ 245

Author(s):

A. P. Tsimpidi ◽

V. A. Karydis ◽

M. Zavala ◽

W. Lei ◽

L. Molina ◽

...

Keyword(s):

Mexico City ◽

Metropolitan Area ◽

Secondary Organic Aerosol ◽

Transport Model ◽

Three Dimensional ◽

Organic Aerosol ◽

Basis Set ◽

Aerosol Formation ◽

Chemical Transport Model ◽

Starting Point

Abstract. New primary and secondary organic aerosol modules have been added to PMCAMx, a three dimensional chemical transport model (CTM), for use with the SAPRC99 chemistry mechanism based on recent smog chamber studies. The new modelling framework is based on the volatility basis-set approach: both primary and secondary organic components are assumed to be semivolatile and photochemically reactive and are distributed in logarithmically spaced volatility bins. This new framework with the use of the new volatility basis parameters for low-NOx and high-NOx conditions tends to predict 4–6 times higher anthropogenic SOA concentrations than those predicted with the older generation of models. The resulting PMCAMx-2008 was applied in Mexico City Metropolitan Area (MCMA) for approximately a week during April 2003 during a period of very low regional biomass burning impact. The emission inventory, which uses as a starting point the MCMA 2004 official inventory, is modified and the primary organic aerosol (POA) emissions are distributed by volatility based on dilution experiments. The predicted organic aerosol (OA) concentrations peak in the center of Mexico City, reaching values above 40 μg m−3. The model predictions are compared with the results of the Positive Matrix Factorization (PMF) analysis of the Aerosol Mass Spectrometry (AMS) observations. The model reproduces both Hydrocarbon-like Organic Aerosol (HOA) and Oxygenated Organic Aerosol (OOA) concentrations and diurnal profiles. The small OA underprediction during the rush-hour periods and overprediction in the afternoon suggest potential improvements to the description of fresh primary organic emissions and the formation of the oxygenated organic aerosols, respectively, although they may also be due to errors in the simulation of dispersion and vertical mixing. However, the AMS OOA data are not specific enough to prove that the model reproduces the organic aerosol observations for the right reasons. Other combinations of contributions of primary and secondary organic aerosol production rates may lead to similar results. The model results strongly suggest that, during the simulated period, transport of OA from outside the city was a significant contributor to the observed OA levels. Future simulations should use a larger domain in order to test whether the regional OA can be predicted with current SOA parameterizations. Sensitivity tests indicate that the predicted OA concentration is especially sensitive to the volatility distribution of the emissions in the lower volatility bins.

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Global modelling of secondary organic aerosol in the troposphere: A sensitivity analysis

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-3-2879-2003 ◽

2003 ◽

Vol 3 (3) ◽

pp. 2879-2929 ◽

Cited By ~ 12

Author(s):

K. Tsigaridis ◽

M. Kanakidou

Keyword(s):

Organic Matter ◽

First Generation ◽

Secondary Organic Aerosol ◽

Transport Model ◽

Organic Aerosol ◽

Oxidation Products ◽

Carbonaceous Aerosols ◽

Temporal And Spatial Distribution ◽

Model Calculations ◽

3 Dimensional

Abstract. A global 3-dimensional chemistry/transport model able to describe O3, NOx, Volatile Organic Compounds (VOC), sulphur and NH3 chemistry has been extended to simulate the temporal and spatial distribution of primary and secondary carbonaceous aerosols in the troposphere focusing on Secondary Organic Aerosol (SOA) formation. A number of global simulations have been performed to determine a possible range of annual global SOA production and investigate uncertainties associated with the model results. Uncertainties in the model calculations related to the enthalpy of vaporization, the solubility and the activity coefficient of the condensable species, the chemical fate of the first generation low volatility oxidation products, the ageing of particles with regard to their hydrophilic properties, the partitioning of SOA on various aerosol surfaces and the evaporation of semi-volatiles from aerosol surfaces have been evaluated. Although not all sources of uncertainties have been investigated, according to our calculations, the above factors within the experimental range of variations could result to an overall uncertainty of about a factor of 20 in the global SOA budget. The global annual SOA production from biogenic VOC might range from 2.5 to 44.5 Tg of organic matter per year, whereas that from anthropogenic VOC ranges from 0.05 to 2.62 Tg of organic matter per year. These estimates can be considered as a lower limit, since partitioning on coarse particles like nitrate, dust or sea-salt, together with the partitioning and the dissociation of the semi-volatile products in aerosol water has been neglected. The large uncertainties associated with the emissions of VOC have not been investigated in this study. Comparison of model results to observations, where available, shows a better agreement for the upper budget estimates than for the lower ones.

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