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.
6 citations
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)...
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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 paper, the authors identify specific compounds that are likely to contribute to the water-soluble fraction by juxtaposing observations regarding the extraction characteristics and the molecular composition of atmospheric particulate organics with compound-specific solubility and condensibility for a wide variety of organics.
Abstract: Although organic compounds typically constitute a substantial fraction of the fine particulate matter (PM) in the atmosphere, their molecular composition remains poorly characterized. This is largely because atmospheric particles contain a myriad of diverse organic compounds, not all of which extract in a single solvent or elute through a gas chromatograph; therefore, a substantial portion typically remains unanalyzed. Most often the chemical analysis is performed on a fraction that extracts in organic solvents such as benzene, ether or hexane; consequently, information on the molecular composition of the water-soluble fraction is particularly sparse and incomplete. This paper investigates theoretically the characteristics of the water-soluble fraction by splicing together various strands of information from the literature. We identify specific compounds that are likely to contribute to the water-soluble fraction by juxtaposing observations regarding the extraction characteristics and the molecular composition of atmospheric particulate organics with compound-specific solubility and condensibility for a wide variety of organics. The results show that water-soluble organics, which constitute a substantial fraction of the total organic mass, include C2 to C7 multifunctional compounds (e.g., diacids, polyols, amino acids). The importance of diacids is already recognized; our results provide an impetus for new experiments to establish the atmospheric concentrations and sources of polyols, amino acids and other oxygenated multifunctional compounds.
1,115 citations
TL;DR: Gas- and particle-phase organic compounds present in the tailpipe emissions from an in-use fleet of gasoline-powered automobiles and light-duty trucks were quantified using a two-stage dilution source sampling system and six isoprenoids and two tricyclic terpanes have been identified as potential tracers for gasoline- powered motor vehicle emissions.
Abstract: Gas- and particle-phase organic compounds present in the tailpipe emissions from an in-use fleet of gasoline-powered automobiles and light-duty trucks were quantified using a two-stage dilution source sampling system. The vehicles were driven through the cold-start Federal Test Procedure (FTP) urban driving cycle on a transient dynamometer. Emission rates of 66 volatile hydrocarbons, 96 semi-volatile and particle-phase organic compounds, 27 carbonyls, and fine particle mass and chemical composition were quantified. Six isoprenoids and two tricyclic terpanes, which are quantified using new source sampling techniques for semi-volatile organic compounds, have been identified as potential tracers for gasoline-powered motor vehicle emissions. A composite of the commercially distributed California Phase II Reformulated Gasoline used in these tests was analyzed by several analytical methods to quantify the gasoline composition, including some organic compounds that are found in the atmosphere as semi-volatile and particle-phase organic compounds. These results allow a direct comparison of the semi-volatile and particle-phase organic compound emissions from gasoline-powered motor vehicles to the gasoline burned by these vehicles. The distribution of n-alkanes and isoprenoids emitted from the catalyst-equipped gasoline-powered vehicles is the same as the distribution of these compounds found in the gasoline used, whereas the distribution of these compounds in the emissions from the noncatalyst vehicles is very different from the distribution in the fuel. In contrast, the distribution of the polycyclic aromatic hydrocarbons and their methylated homologues in the gasoline is significantly different from the distribution of the PAH in the tailpipe emissions from both types of vehicles.
1,007 citations
TL;DR: In this paper, the IMPROVE and NIOSH thermal evolution protocols were applied to 60 ambient and source samples from different environments using the same instrument to quantify differences in implemented protocols.
Abstract: Organic carbon (OC) and elemental carbon (EC) are operationally defined by the analysis methods, and different methods give in different results. The IMPROVE (Interagency Monitoring of Protected Visual Environments) and NIOSH (National Institute of Occupational Safety and Health) thermal evolution protocols present different operational definitions. These protocols are applied to 60 ambient and source samples from different environments using the same instrument to quantify differences in implemented protocols on the same instrument. The protocols are equivalent for total carbon sampled on quartz-fiber filters. NIOSH EC was typically less than half of IMPROVE EC. The primary difference is the allocation of carbon evolving at the NIOSH 850°C temperature in a helium atmosphere to the OC rather than EC fraction. Increasing light transmission and reflectance during this temperature step indicate that this fraction should be classified as EC. When this portion of NIOSH OC is added to NIOSH EC, the IMPROVE and ...
857 citations
TL;DR: A dilution stack sampler specifically intended to collect fine organic aerosol from combustion sources while minimizing sample contamination has been designed and tested as mentioned in this paper, which simulates the cooling and dilution processes that occur in the plume downwind of a combustion source, so that the organic compounds which condense under ambient conditions will be collected as particulate matter.
Abstract: A dilution stack sampler specifically intended to collect fine organic aerosol from combustion sources while minimizing sample contamination has been designed and tested. The sampler simulates the cooling and dilution processes that occur in the plume downwind of a combustion source, so that the organic compounds which condense under ambient conditions will be collected as particulate matter. The special features of this sampler are described in detail, and compared with other stack sampling systems. The results of both laboratory and field tests of the system are discussed. Collection of organic aerosol using this sampler is compared with collection using EPA Method 5.
218 citations
TL;DR: In this article, the sensitivity of organic aerosol (OA, and its components) mass to changes in temperature were measured using a tandem thermodenuder-aerosol mass spectrometer (TD-AMS) system in Mexico City and the Los Angeles area.
Abstract: . Measurements of the sensitivity of organic aerosol (OA, and its components) mass to changes in temperature were recently reported by Huffman et al.~(2009) using a tandem thermodenuder-aerosol mass spectrometer (TD-AMS) system in Mexico City and the Los Angeles area. Here, we use these measurements to derive quantitative estimates of aerosol volatility within the framework of absorptive partitioning theory using a kinetic model of aerosol evaporation in the TD. OA volatility distributions (or "basis-sets") are determined using several assumptions as to the enthalpy of vaporization (ΔHvap). We present two definitions of "non-volatile OA," one being a global and one a local definition. Based on these definitions, our analysis indicates that a substantial fraction of the organic aerosol is comprised of non-volatile components that will not evaporate under any atmospheric conditions; on the order of 50–80% when the most realistic ΔHvap assumptions are considered. The sensitivity of the total OA mass to dilution and ambient changes in temperature has been assessed for the various ΔHvap assumptions. The temperature sensitivity is relatively independent of the particular ΔHvap assumptions whereas dilution sensitivity is found to be greatest for the low (ΔHvap = 50 kJ/mol) and lowest for the high (ΔHvap = 150 kJ/mol) assumptions. This difference arises from the high ΔHvap assumptions yielding volatility distributions with a greater fraction of non-volatile material than the low ΔHvap assumptions. If the observations are fit using a 1 or 2-component model the sensitivity of the OA to dilution is unrealistically high. An empirical method introduced by Faulhaber et al. (2009) has also been used to independently estimate a volatility distribution for the ambient OA and is found to give results consistent with the high and variable ΔHvap assumptions. Our results also show that the amount of semivolatile gas-phase organics in equilibrium with the OA could range from ~20% to 400% of the OA mass, with smaller values generally corresponding to the higher ΔHvap assumptions. The volatility of various OA components determined from factor analysis of AMS spectra has also been assessed. In general, it is found that the fraction of non-volatile material follows the pattern: biomass burning OA
216 citations