Primary Organic Aerosols
01 Jan 2018-pp 109-117
TL;DR: In this article, a two-dimensional volatility basis scheme (2-D-VBS) was proposed to simulate the gas-particle partitioning by employing the vapor pressure and degree of oxygenation.
Abstract: Primary organic aerosol (POA) constitutes the emissions from both natural (vegetation and micro-organisms) and anthropogenic sources such as combustion of fossil fuels and biofuels, and open biomass burning (forest fire). Semi-volatile nature of POA emissions leads to overestimation in the traditional emission inventories and chemical transport models. Another class of primarily emitted volatile species, i.e., intermediate volatile organic compounds (IVOCs), present around 0.28–2.5 times of POA, potential secondary organic aerosols (SOAs) precursors, also goes unnoticed. Phase partitioning mechanisms depending on their source, dilution, and volatility distribution make the contribution of POA to overall organic aerosols (OA) budget controversial. Further, the complex and higher particle emission rates and the gas-phase chemical transformation processes lead to the conceptual ambiguity between primary and secondary organic aerosol, thus rendering physico-chemical and optical properties to be least understood. Researchers have overcome the need of complete molecular identification of gaseous species to simulate the gas-particle partitioning by developing a two-dimensional volatility basis scheme (2-D-VBS) that employs the vapor pressure and degree of oxygenation. Here, we also illustrate the chemical composition-dependent volatility distributions for different sources used to ascertain the correct POA emission factors. This suggest that the policymakers and environmental regulating authorities need to take into account the SVOCs and IVOCs causing positive and negative sampling artifacts in order to correctly account for POA source contributions.
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TL;DR: In this article, the chemical composition and volatility of organic aerosol (OA) particles were investigated during July-August 2017 and February-March 2018 in the city of Stuttgart, one of the most polluted cities in Germany.
Abstract: . The chemical composition and volatility of organic aerosol (OA)
particles were investigated during July–August 2017 and February–March
2018 in the city of Stuttgart, one of the most polluted cities in Germany.
Total non-refractory particle mass was measured with a high-resolution
time-of-flight aerosol mass spectrometer (HR-ToF-AMS; hereafter AMS).
Aerosol particles were collected on filters and analyzed in the laboratory
with a filter inlet for gases and aerosols coupled to a high-resolution
time-of-flight chemical ionization mass spectrometer (FIGAERO-HR-ToF-CIMS;
hereafter CIMS), yielding the molecular composition of oxygenated OA (OOA)
compounds. While the average organic mass loadings are lower in the summer
period ( 5.1±3.2 µ g m −3 ) than in the winter period ( 8.4±5.6 µ g m −3 ), we find relatively larger mass
contributions of organics measured by AMS in summer ( 68.8±13.4 %)
compared to winter ( 34.8±9.5 %). CIMS mass spectra show OOA
compounds in summer have O : C of 0.82±0.02 and are more influenced by
biogenic emissions, while OOA compounds in winter have O : C of 0.89±0.06 and are more influenced by biomass burning emissions. Volatility
parametrization analysis shows that OOA in winter is less volatile with
higher contributions of low-volatility organic compounds (LVOCs) and extremely
low-volatility organic compounds (ELVOCs). We partially explain this by the
higher contributions of compounds with shorter carbon chain lengths and
a higher number of oxygen atoms, i.e., higher O : C in winter. Organic compounds
desorbing from the particles deposited on the filter samples also exhibit a
shift of signal to higher desorption temperatures (i.e., lower apparent
volatility) in winter. This is consistent with the relatively higher O : C in
winter but may also be related to higher particle viscosity due to the
higher contributions of larger-molecular-weight LVOCs and ELVOCs, interactions
between different species and/or particles (particle matrix), and/or thermal
decomposition of larger molecules. The results suggest that whereas lower
temperature in winter may lead to increased partitioning of semi-volatile
organic compounds (SVOCs) into the particle phase, this does not result in a
higher overall volatility of OOA in winter and that the difference in
sources and/or chemistry between the seasons plays a more important role.
Our study provides insights into the seasonal variation of the molecular
composition and volatility of ambient OA particles and into their potential
sources.
30 citations
Cites background from "Primary Organic Aerosols"
...POA is dominated by vehicular emissions in urban 55 environments (Bhattu, 2018)....
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TL;DR: The optical properties of aerosols were investigated using multi-year analysis from the Ilorin AERONET site (8.320° N, 4.340° E) in Nigeria, in tropical West Africa.
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TL;DR: In this article, the morphological and elemental compositions of individual particles in seven micro-environments of Xi'an were characterized using a morphological-and elemental-based approach.
Abstract: This paper characterizes the morphological and elemental compositions of individual particles in seven micro-environments of Xi’an. Atmospheric particulate matter samples were collected at one subu...
5 citations
Cites background from "Primary Organic Aerosols"
...These particles could come from both natural (vegetation and microorganisms) and anthropogenic sources such as combustion of fossil fuels and biofuels, and open biomass burning.(25)...
[...]
TL;DR: In this paper , the results from a set of aerosol and gas-phase measurements collected during the BIO-MAÏDO field campaign in Réunion between March 8 and April 5, 2019 were presented.
Abstract: This work presents the results from a set of aerosol- and gas-phase measurements collected during the BIO-MAÏDO field campaign in Réunion between March 8 and April 5, 2019. Several offline and online sampling devices were installed at the Maïdo Observatory (MO), a remote high-altitude site in the Southern Hemisphere, allowing the physical and chemical characterization of atmospheric aerosols and gases. The evaluation of short-lived gas-phase measurements allows us to conclude that air masses sampled during this period contained little or no anthropogenic influence. The dominance of sulfate and organic species in the submicron fraction of the aerosol is similar to that measured at other coastal sites. Carboxylic acids on PM10 showed a significant contribution of oxalic acid, a typical tracer of aqueous processed air masses, increasing at the end of the campaign. This result agrees with the positive matrix factorization analysis of the submicron organic aerosol, where more oxidized organic aerosols (MOOAs) dominated the organic aerosol with an increasing contribution toward the end of the campaign. Using a combination of air mass trajectories (model predictions), it was possible to assess the impact of aqueous phase processing on the formation of secondary organic aerosols (SOAs). Our results show how specific chemical signatures and physical properties of air masses, possibly affected by cloud processing, can be identified at Réunion. These changes in properties are represented by a shift in aerosol size distribution to large diameters and an increased contribution of secondary sulfate and organic aerosols after cloud processing.
1 citations
References
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TL;DR: In this paper, the evolution of the VUV mass spectra for two distinct organic aerosol types with temperature is observed to differ dramatically, and the authors postulate that this difference arises from diffusivity within the α-pinene + O 3 reaction (αP).
Abstract: . Vacuum Ultraviolet (VUV) photoionization mass spectrometry has been used to measure the evolution of chemical composition for two distinct organic aerosol types as they are passed through a thermodenuder at different temperatures. The two organic aerosol types considered are primary lubricating oil (LO) aerosol and secondary aerosol from the α-pinene + O 3 reaction (αP). The evolution of the VUV mass spectra for the two aerosol types with temperature are observed to differ dramatically. For LO particles, the spectra exhibit distinct changes with temperature in which the lower m/z peaks, corresponding to compounds with higher vapor pressures, disappear more rapidly than the high m/z peaks. In contrast, the αP aerosol spectrum is essentially unchanged by temperature even though the particles experience significant mass loss due to evaporation. The variations in the LO spectra are found to be quantitatively in agreement with expectations from absorptive partitioning theory whereas the αP spectra suggest that the evaporation of αP derived aerosol appears to not be governed by partitioning theory. We postulate that this difference arises from diffusivity within the αP particles being sufficiently slow that they do not exhibit the expected liquid-like behavior and perhaps exist in a glassy state. To reconcile these observations with decades of aerosol growth measurements, which indicate that OA formation is described by equilibrium partitioning, we present a conceptual model wherein the secondary OA is formed and then rapidly converted from an absorbing form to a non-absorbing form. The results suggest that, although OA growth may be describable by equilibrium partitioning theory, the properties of organic aerosol once formed may differ significantly from the properties determined in the equilibrium framework.
194 citations
TL;DR: In this article, heating and dilution were used to investigate the volatility of biomass-burning smoke particles from combustion of common North American trees/shrubs/grasses during the third Fire Lab at Missoula Experiment.
Abstract: [1] Atmospheric organic aerosol concentrations depend in part on the gas-particle partitioning of primary organic aerosol (POA) emissions. Consequently, heating and dilution were used to investigate the volatility of biomass-burning smoke particles from combustion of common North American trees/shrubs/grasses during the third Fire Lab at Missoula Experiment. Fifty to eighty percent of the mass of biomass-burning POA evaporated when isothermally diluted from plume- (~1000 µg m−3) to ambient-like concentrations (~10 µg m−3), while roughly 80% of the POA evaporated upon heating to 100°C in a thermodenuder with a residence time of ~14 sec. Therefore, the majority of the POA emissions were semivolatile. Thermodenuder measurements performed at three different residence times indicated that there were not substantial mass transfer limitations to evaporation (i.e., the mass accommodation coefficient appears to be between 0.1 and 1). An evaporation kinetics model was used to derive volatility distributions and enthalpies of vaporization from the thermodenuder data. A single volatility distribution can be used to represent the measured gas-particle partitioning from the entire set of experiments, including different fuels, organic aerosol concentrations, and thermodenuder residence times. This distribution, derived from the thermodenuder measurements, also predicts the dilution-driven changes in gas-particle partitioning. This volatility distribution and associated emission factors for each fuel studied can be used to update emission inventories and to simulate the gas-particle partitioning of biomass-burning POA emissions in chemical transport models.
194 citations
TL;DR: This review paper is designed as a guide for those wishing to learn about the current state of black carbon measurement instrumentation, how calibration is carried out, when one instrument may have the advantage over another, and where new techniques are needed to fill important knowledge gaps.
Abstract: Elemental-, equivalent black- and refractory black-carbon are terms that have been defined in order to dissect the more general term, black carbon, into its component parts related to its specific chemical and optical properties and its impact on climate and health. Recent publications have attempted to clarify the meaning of these terms with respect to their environmental impact, particularly on climate. Here, we focus on the measurement aspects, reviewing the most commonly implemented techniques for the direct and indirect derivation of black carbon properties, their strengths, limitations, and uncertainties, and provide a non-exhaustive bibliography where the reader can find more detailed information. This review paper is designed as a guide for those wishing to learn about the current state of black carbon measurement instrumentation, how calibration is carried out, when one instrument may have the advantage over another, and where new techniques are needed to fill important knowledge gaps.
192 citations
Journal Article•
TL;DR: In this paper, the evolution of the VUV mass spectra for primary lubricating oil (LO) and secondary aerosol from the alpha-pinene + O3 reaction (alphaP) was studied.
Abstract: Vacuum Ultraviolet (VUV) photoionization mass spectrometry has been used to measure the evolution of chemical composition for two distinct organic aerosol types as they are passed through a thermodenuder at different temperatures. The two organic aerosol types considered are primary lubricating oil (LO) aerosol and secondary aerosol from the alpha-pinene + O3 reaction (alphaP). The evolution of the VUV mass spectra for the two aerosol types with temperature are observed to differ dramatically. For LO particles, the spectra exhibit distinct changes with temperature in which the lower m/z peaks, corresponding to compounds with higher vapor pressures, disappear more rapidly than the high m/z peaks. In contrast, the alphaP aerosol spectrum is essentially unchanged by temperature even though the particles experience significant mass loss due to evaporation. The variations in the LO spectra are found to be quantitatively in agreement with expectations from absorptive partitioning theory whereas the alphaP spectra suggest that the evaporation of alphaP derived aerosol appears to not be governed by partitioning theory. We postulate that this difference arises from the alphaP particles existing as in a glassy state instead of having the expected liquid-like behavior. To reconcile these observations with decades of aerosol growth measurements, which indicate that OA formation is described by equilibrium partitioning, we present a conceptual model wherein the secondary OA is formed and then rapidly converted from an absorbing form to a non-absorbing form. The results suggest that although OA growth may be describable by equilibrium partitioning theory, the properties of organic aerosol once formed may differ significantly from the properties determined in the equilibrium framework.
187 citations
TL;DR: In this article, the evaporation of three organic aerosol types (adipic acid, α-pinene SOA and aged OA) inside a thermodenuder with a mass transfer model, and calculated equilibration time scales for these systems at realistic conditions.
149 citations