Elemental composition of organic aerosol: The gap between ambient and laboratory measurements

Chen, Qi; Heald, Colette L.; Jimenez, José L.; Canagaratna, Manjula R.; Zhang, Qi; He, Longhui; Huang, Xinyi; Campuzano‐Jost, Pedro; Palm, Brett B.; Poulain, Laurent; Kuwata, Mikinori; Martin, Scot T.; Abbatt, Jonathan P. D.; Lee, Alex K. Y.; Liggio, John

doi:10.1002/2015gl063693

Cited by 93 publications

(105 citation statements)

References 66 publications

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“…Aerosol elemental ratios measured with the AMS have been previously used to distinguish between different types of organic aerosol Ng et al, 2010), examine the degree to which chamber SOA is able to simulate ambient SOA (Chhabra et al, 2010;Ng et al, 2010), and to constrain oxidation mechanisms used in theoretical models Kroll et al, 2011;Donahue et al, 2011;Daumit et al, 2013;Chen et al, 2014). Here we show that while the changes introduced by the Improved-Ambient method can be significant, they do not change any fundamental conclusions made from previous AMS studies.…”

Section: Atmospheric Implicationsmentioning

confidence: 50%

“…The Improved-Ambient method yields van Krevelen slopes that are approximately 20 % shallower than those determined with the Ambient-Aiken method. Details are discussed in Chen et al, 2014. These slopes (−0.8 for total OA and −0.4 for OOA) suggest that the ambient OA oxidative mechanisms involve different net addition of -OH and/or -OOH functionalities and fragmentation than previously assumed.…”

Section: Effect Of Improved-ambient Methods On Previous Measurements Omentioning

confidence: 78%

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Elemental ratio measurements of organic compounds using aerosol mass spectrometry: characterization, improved calibration, and implications

et al. 2015

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Abstract. Elemental compositions of organic aerosol (OA) particles provide useful constraints on OA sources, chemical evolution, and effects. The Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) is widely used to measure OA elemental composition. This study evaluates AMS measurements of atomic oxygento-carbon (O : C), hydrogen-to-carbon (H : C), and organic mass-to-organic carbon (OM : OC) ratios, and of carbon oxidation state (OS C ) for a vastly expanded laboratory data set of multifunctional oxidized OA standards. For the expanded standard data set, the method introduced by Aiken et al. (2008), which uses experimentally measured ion intensities at all ions to determine elemental ratios (referred to here as "Aiken-Explicit"), reproduces known O : C and H : C ratio values within 20 % (average absolute value of relative errors) and 12 %, respectively. The more commonly used method, which uses empirically estimated H 2 O + and CO + ion intensities to avoid gas phase air interferences at these ions (referred to here as "Aiken-Ambient"), reproduces O : C and H : C of multifunctional oxidized species within 28 and 14 % of known values. The values from the latter method are systematically biased low, however, with larger biases observed for alcohols and simple diacids. A detailed examination of the H 2 O + , CO + , and CO + 2 fragments in the high-resolution mass spectra of the standard compounds indicates that the Aiken-Ambient method underestimates the CO + and especially H 2 O + produced from many oxidized species. Combined AMS-vacuum ultraviolet (VUV) ionization measurements indicate that these ions are produced by dehydration and decarboxylation on the AMS vaporizer (usually operated at 600 • C). Thermal decomposition is observed to be efficient at vaporizer temperatures down to 200 • C. These results are used together to develop an "Improved-Ambient" elemental analysis method for AMS spectra measured in air. The Improved-Ambient method uses specific ion fragments as markers to correct for molecular functionality-dependent systematic biases and reproduces known O : C (H : C) ratios of individual oxidized standards within 28 % (13 %) of the known molecular values. The error in Improved-Ambient O : C (H : C) values is smaller for theoretical standard mixtures of the oxidized organic standards, which are more representative of the complex mix of species present in ambient Published by Copernicus Publications on behalf of the European Geosciences Union. M. R. Canagaratna et al.: Elemental ratio measurements of organic compoundsOA. For ambient OA, the Improved-Ambient method produces O : C (H : C) values that are 27 % (11 %) larger than previously published Aiken-Ambient values; a corresponding increase of 9 % is observed for OM : OC values. These results imply that ambient OA has a higher relative oxygen content than previously estimated. The OS C values calculated for ambient OA by the two methods agree well, however (average relative difference of 0.06 OS C units). This indicates that...

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Section: Atmospheric Implicationsmentioning

confidence: 50%

Section: Effect Of Improved-ambient Methods On Previous Measurements Omentioning

confidence: 78%

Elemental ratio measurements of organic compounds using aerosol mass spectrometry: characterization, improved calibration, and implications

et al. 2015

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“…The O : C vs. H : C ratios can be fitted by a line with a slope of −0.63 and an intercept of 1.95 by the reduced-major-axis (RMA) regression method. The V-K diagram for OA summarized by Chen et al (2015) is also given in Fig. 9 in order to make comparisons between OA measured in Beijing and in other atmospheric environments.…”

Section: Closure Between Particle Hygroscopicity and Chemical Componentsmentioning

confidence: 99%

“…9 in order to make comparisons between OA measured in Beijing and in other atmospheric environments. Chen et al (2015) found that ambient organic aerosols line up in the V-K space along a line with a slope of −0.6 by synthesizing a large data set of surface field observations covering urban, rural, and remote environments. The trajectory Atmos.…”

Section: Closure Between Particle Hygroscopicity and Chemical Componentsmentioning

confidence: 99%

Particle hygroscopicity and its link to chemical composition in the urban atmosphere of Beijing, China, during summertime

et al. 2016

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Abstract. Simultaneous measurements of particle number size distribution, particle hygroscopic properties, and size-resolved chemical composition were made during the summer of 2014 in Beijing, China. During the measurement period, the mean hygroscopicity parameters (κs) of 50, 100, 150, 200, and 250 nm particles were respectively 0.16 ± 0.07, 0.19 ± 0.06, 0.22 ± 0.06, 0.26 ± 0.07, and 0.28 ± 0.10, showing an increasing trend with increasing particle size. Such size dependency of particle hygroscopicity was similar to that of the inorganic mass fraction in PM 1 . The hydrophilic mode (hygroscopic growth factor, HGF > 1.2) was more prominent in growth factor probability density distributions and its dominance of hydrophilic mode became more pronounced with increasing particle size. When PM 2.5 mass concentration was greater than 50 µg m −3 , the fractions of the hydrophilic mode for 150, 250, and 350 nm particles increased towards 1 as PM 2.5 mass concentration increased. This indicates that aged particles dominated during severe pollution periods in the atmosphere of Beijing. Particle hygroscopic growth can be well predicted using hightime-resolution size-resolved chemical composition derived from aerosol mass spectrometer (AMS) measurements using the Zdanovskii-Stokes-Robinson (ZSR) mixing rule. The organic hygroscopicity parameter (κ org ) showed a positive correlation with the oxygen to carbon ratio. During the new particle formation event associated with strongly active photochemistry, the hygroscopic growth factor or κ of newly formed particles is greater than for particles with the same sizes not during new particle formation (NPF) periods. A quick transformation from external mixture to internal mixture for pre-existing particles (for example, 250 nm particles) was observed. Such transformations may modify the state of the mixture of pre-existing particles and thus modify properties such as the light absorption coefficient and cloud condensation nuclei activation.

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“…Modeling has shown that including cloud processing reactions improves prediction of secondary organic aerosol (SOA) mass concentrations . However, there is substantial inconsistency between the chemical composition of laboratory-generated and ambient organic aerosol, in part likely due to aqueous processing (Chen et al, 2015). Potential products of aqueous processing include carboxylic acids, esters, organosulfur compounds, polyols, amines, amino acids, and highly oxygenated oligomeric species (Blando and Turpin, 2000;Ervens et al, 2011).…”

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confidence: 99%

Biogenic, urban, and wildfire influences on the molecular composition of dissolved organic compounds in cloud water

Cook¹,

Lin²,

Peng³

et al. 2017

Atmos. Chem. Phys.

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Abstract. Organic aerosol formation and transformation occurs within aqueous aerosol and cloud droplets, yet little is known about the composition of high molecular weight organic compounds in cloud water. Cloud water samples collected at Whiteface Mountain, New York, during AugustSeptember 2014 were analyzed by ultra-high-resolution mass spectrometry to investigate the molecular composition of dissolved organic carbon, with a focus on sulfur-and nitrogen-containing compounds. Organic molecular composition was evaluated in the context of cloud water inorganic ion concentrations, pH, and total organic carbon concentrations to gain insights into the sources and aqueous-phase processes of the observed high molecular weight organic compounds. Cloud water acidity was positively correlated with the average oxygen : carbon ratio of the organic constituents, suggesting the possibility for aqueous acid-catalyzed (prior to cloud droplet activation or during/after cloud droplet evaporation) and/or radical (within cloud droplets) oxidation processes. Many tracer compounds recently identified in laboratory studies of bulk aqueous-phase reactions were identified in the cloud water. Organosulfate compounds, with both biogenic and anthropogenic volatile organic compound precursors, were detected for cloud water samples influenced by air masses that had traveled over forested and populated areas. Oxidation products of long-chain (C 10−12 ) alkane precursors were detected during urban influence. Influence of Canadian wildfires resulted in increased numbers of identified sulfur-containing compounds and oligomeric species, including those formed through aqueous-phase reactions involving methylglyoxal. Light-absorbing aqueous-phase products of syringol and guaiacol oxidation were observed in the wildfire-influenced samples, and dinitroaromatic compounds were observed in all cloud water samples (wildfire, biogenic, and urban-influenced). Overall, the cloud water molecular composition depended on air mass source influence and reflected aqueous-phase reactions involving biogenic, urban, and biomass burning precursors.

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Elemental composition of organic aerosol: The gap between ambient and laboratory measurements

Cited by 93 publications

References 66 publications

Elemental ratio measurements of organic compounds using aerosol mass spectrometry: characterization, improved calibration, and implications

Elemental ratio measurements of organic compounds using aerosol mass spectrometry: characterization, improved calibration, and implications

Particle hygroscopicity and its link to chemical composition in the urban atmosphere of Beijing, China, during summertime

Biogenic, urban, and wildfire influences on the molecular composition of dissolved organic compounds in cloud water

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