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: 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.
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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)...
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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 article, the authors reviewed existing knowledge with regard to organic aerosol (OA) of importance for global climate modelling and defined critical gaps needed to reduce the involved uncertainties, and synthesized the information to provide a continuous analysis of the flow from the emitted material to the atmosphere up to the point of the climate impact of the produced organic aerosols.
Abstract: The present paper reviews existing knowledge with regard to Organic Aerosol (OA) of importance for global climate modelling and defines critical gaps needed to reduce the involved uncertainties. All pieces required for the representation of OA in a global climate model are sketched out with special attention to Secondary Organic Aerosol (SOA): The emission estimates of primary carbonaceous particles and SOA precursor gases are summarized. The up-to-date understanding of the chemical formation and transformation of condensable organic material is outlined. Knowledge on the hygroscopicity of OA and measurements of optical properties of the organic aerosol constituents are summarized. The mechanisms of interactions of OA with clouds and dry and wet removal processes parameterisations in global models are outlined. This information is synthesized to provide a continuous analysis of the flow from the emitted material to the atmosphere up to the point of the climate impact of the produced organic aerosol. The sources of uncertainties at each step of this process are highlighted as areas that require further studies.
2,863 citations
TL;DR: This article presented a bottom-up estimate of uncertainties in source strength by combining uncertainties in particulate matter emission factors, emission characterization, and fuel use, with uncertainty ranges of 4.3-22 Tg/yr for BC and 17-77 Tg /yr for OC.
Abstract: [1] We present a global tabulation of black carbon (BC) and primary organic carbon (OC) particles emitted from combustion. We include emissions from fossil fuels, biofuels, open biomass burning, and burning of urban waste. Previous ‘‘bottom-up’’ inventories of black and organic carbon have assigned emission factors on the basis of fuel type and economic sector alone. Because emission rates are highly dependent on combustion practice, we consider combinations of fuel, combustion type, and emission controls and their prevalence on a regional basis. Central estimates of global annual emissions are 8.0 Tg for black carbon and 33.9 Tg for organic carbon. These estimates are lower than previously published estimates by 25–35%. The present inventory is based on 1996 fuel-use data, updating previous estimates that have relied on consumption data from 1984. An offset between decreased emission factors and increased energy use since the base year of the previous inventory prevents the difference between this work and previous inventories from being greater. The contributions of fossil fuel, biofuel, and open burning are estimated as 38%, 20%, and 42%, respectively, for BC, and 7%, 19%, and 74%, respectively, for OC. We present a bottom-up estimate of uncertainties in source strength by combining uncertainties in particulate matter emission factors, emission characterization, and fuel use. The total uncertainties are about a factor of 2, with uncertainty ranges of 4.3–22 Tg/yr for BC and 17–77 Tg/yr for OC. Low-technology combustion contributes greatly to both the emissions and the uncertainties. Advances in emission characterization for small residential, industrial, and mobile sources and topdown analysis combining field measurements and transport modeling with iterative inventory development will be required to reduce the uncertainties further. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0360 Atmospheric Composition and Structure: Transmission and scattering of radiation; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; KEYWORDS: emission, black carbon, organic carbon, fossil fuel, biofuel, biomass burning
2,180 citations
TL;DR: In this article, a thermal-optical technique for analysis of the carbonaceous fraction of particulate diesel exhaust is reported, and the speciation of organic and elemental carbon is accomplished through temperature and atmosphere control, and by an optical feature that corrects for pyrolytically generated carbon.
Abstract: Diesel exhaust has been classified a probable human carcinogen, and the National Institute for Occupational Safety and Health (NIOSH) has recommended that employers reduce workers' exposures. Because diesel exhaust is a chemically complex mixture containing thousands of compounds, some measure of exposure must be selected. Previously used methods involving gravimetry or analysis of the soluble organic fraction of diesel soot lack adequate sensitivity and selectivity for low-level determination of particulate diesel exhaust; a new analytical approach was therefore needed. In this paper, results of investigation of a thermal-optical technique for analysis of the carbonaceous fraction of particulate diesel exhaust are reported. With this technique, speciation of organic and elemental carbon is accomplished through temperature and atmosphere control, and by an optical feature that corrects for pyrolytically generated carbon, or “char,” which is formed during the analysis of some materials. The therma...
1,749 citations
TL;DR: In this article, two important aerosol species, sulfate and organic particles, have large natural biogenic sources that depend in a highly complex fashion on environmental and ecological parameters and therefore are prone to influence by global change.
Abstract: Atmospheric aerosols play important roles in climate and atmospheric chemistry: They scatter sunlight, provide condensation nuclei for cloud droplets, and participate in heterogeneous chemical reactions. Two important aerosol species, sulfate and organic particles, have large natural biogenic sources that depend in a highly complex fashion on environmental and ecological parameters and therefore are prone to influence by global change. Reactions in and on sea-salt aerosol particles may have a strong influence on oxidation processes in the marine boundary layer through the production of halogen radicals, and reactions on mineral aerosols may significantly affect the cycles of nitrogen, sulfur, and atmospheric oxidants.
1,589 citations
TL;DR: Accounting for partitioning and photochemical processing of primary emissions creates a more regionally distributed aerosol and brings model predictions into better agreement with observations, attribute this unexplained secondary organic-aerosol production to the oxidation of low-volatility gas-phase species.
Abstract: Most primary organic-particulate emissions are semivolatile; thus, they partially evaporate with atmospheric dilution, creating substantial amounts of low-volatility gas-phase material. Laboratory experiments show that photo-oxidation of diesel emissions rapidly generates organic aerosol, greatly exceeding the contribution from known secondary organic-aerosol precursors. We attribute this unexplained secondary organic-aerosol production to the oxidation of low-volatility gas-phase species. Accounting for partitioning and photochemical processing of primary emissions creates a more regionally distributed aerosol and brings model predictions into better agreement with observations. Controlling organic particulate-matter concentrations will require substantial changes in the approaches that are currently used to measure and regulate emissions.
1,563 citations