Ambient black carbon particle hygroscopic properties controlled by mixing state and composition

Liu, Dantong; Allan, J. D.; Whitehead, J. D.; Young, D. E.; Flynn, Michael J.; Coe, Hugh; McFiggans, G.; Fleming, Zoë L.; Bandy, B. J.

doi:10.5194/acp-13-2015-2013

Cited by 181 publications

(223 citation statements)

References 56 publications

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“…Both regional background sources and urban (local) emissions contribute to these particles (Swietlicki et al, 2008), which can result in more complex situations. The whole explanation is also consistent with the fact that the mixing state of soot particles is largely determined at their sources (Liu et al, 2013). The relative concentration of Vmode particles was increased from 66% to 79% with diameter, and this was accompanied by a modest decrease in volatility.…”

supporting

confidence: 70%

“…It is worth realising that the GFs for pure (NH4)2SO4 and NH4NO3 (Park et al, 2009) are substantially larger than the measured values, which indicate considerable abundance of less hygroscopic species that are internally mixed with the inorganic salts. These particles can be composed of moderately transformed aged soot-containing combustion particles comprising also partly oxygenated organics and inorganic salts (Duplissy et al, 2011; 20 Liu et al, 2013). This view is further confirmed by a high-resolution TEM/EDS study of individual particles at the BpART facility (Németh et al, 2015).…”

supporting

confidence: 50%

“…The studies also reported the presence of a MH mode, which was not present in our data set. This mode is attributed in most cases either to the aged continental mostly soot-free background aerosol particles (Liu et al, 2013) entering the urban air or to particles from efficient biomass burning (BB; Swietlicki et al, 2008). The missing MH mode in the Budapest data suggests that the particles from local urban and rural regional sources seem more important inside the city than that from 5 continental background sources, and the distance from the sea can possibly play a role as well.…”

mentioning

confidence: 96%

“…The situation was similar for the LV mode, thus the mean GF stayed constant at approximately 0.96 independently of the particle size, while the particle number fraction in the mode was decreasing, although its extent was less pronounced, from 34% to 21%. The NH mode and the LV mode were related to freshly emitted combustion 40 particles consisting of large mass fractions of soot and some water-insoluble organic compounds (Liu et al, 2013). The latter species can be a mixture of non-hygroscopic Hydrocarbon-like Organic Aerosol (HOA) in the condensed phase and adsorbed Volatile Organic Compounds (VOCs) in a huge number from the gas phase.…”

mentioning

confidence: 99%

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Winter time hygroscopicity and volatility of ambient urban aerosol particles

Enroth¹,

Mikkilä²,

Németh³

et al. 2017

Preprint

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Abstract. Hygroscopic and volatile properties of atmospheric aerosol particles with dry diameters of (20), 50, 75, 110 and 145 nm were determined in situ by using a VH-TDMA system with a relative humidity of 90% and denuding temperature of 270 C in central Budapest during two months in winter 2014-2015. The probability density function of the hygroscopic growth factor (GF) showed a distinct bimodal distribution. One of the modes was characterised by an overall mean GF of 10 approximately 1.07 (the corresponding hygroscopicity parameter  of 0.033) independently of the particle size, and was assigned to nearly hydrophobic (NH) particles. Its mean particle number fraction was large, and it was decreasing monotonically from 71% to 41% with particle diameter. The other mode showed a mean GF increasing slightly from 1.31 to 1.38 ( values from 0.186 to 0.196) with particle diameter, and it was attributed to less hygroscopic (LH) particles. These hygroscopicity values are low in general. The mode with more hygroscopic particles was not identified. The probability density 15 function of the volatility GF also exhibited a distinct bimodal distribution with an overall mean volatility GF of approximately 0.96 independently of the particle size, and with another mean GF increasing from 0.49 to 0.55 with particle diameter. The two modes were associated with less volatile (LV) and volatile (V) particles. The mean particle number fraction for the LV mode was decreasing from 34% to 21% with particle diameter. The bimodal distributions in the GF spectrum indicated that the urban atmospheric aerosol contained an external mixture of particles with a diverse chemical composition. The mean 20 diurnal variability of the particle number fractions for the NH and LV modes, and of the volatility GF for the LV mode followed the diurnal pattern of the vehicular road traffic, while the mean diurnal variability of the hygroscopicity parameter for the NH, and of the particle number fractions for the V mode on workdays were inversely linked to the road traffic. The particles corresponding to the NH and LV modes were assigned mainly to freshly emitted combustion particles, more specifically to vehicle emissions consisting of large mass fractions of soot likely coated with or containing some water-insoluble organic 25 compounds such as non-hygroscopic hydrocarbon-like organics. The particles related to the LH and V modes could be composed of moderately transformed aged combustion particles consisting of partly oxygenated organics, inorganic salts and soot. Both regional background sources and urban (local) emissions contribute to these particles. Dependency of the volatility GF and the volume fraction remaining after the thermal treatment on the mean hygroscopic GF suggested that the hygroscopic compounds were ordinarily volatile, and that the larger particles contained internally mixed non-volatile chemical species as 30 refractory residuals in 20-25% of the aerosol material (by volume), which could be core-like soot or organic polymers.

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supporting

confidence: 70%

supporting

confidence: 50%

mentioning

confidence: 96%

mentioning

confidence: 99%

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Winter time hygroscopicity and volatility of ambient urban aerosol particles

Enroth¹,

Mikkilä²,

Németh³

et al. 2017

Preprint

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“…Organic coatings can be formed on BC through condensation and/or coagulation of co-emitted primary organic aerosol (POA) and secondary organic aerosol (SOA) produced via photochemical processing. The hydrophilic nature of SOA coating has been shown to modify hygroscopicity of ambient BC for cloud droplet activation (Kuwata et al, 2009;McMeeking et al, 2011;Laborde et al, 2013;Liu et al, 2013). Increasing coating thickness may enhance light absorption of BC due to a "lensing effect" depending on the degree of particle aging (Jacobson, 2001;Cappa et al, 2012;Peng et al, 2016;Liu et al, 2017) and alter BC morphology from highly fractal to compact structures and thus their aerodynamic properties (Moffet and Prather, 2009;Schnitzler et al, 2014;Guo et al, 2016;Peng et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Formation of secondary organic aerosol coating on black carbon particles near vehicular emissions

Lee

Chen

et al. 2017

Atmos. Chem. Phys.

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Abstract. Black carbon (BC) emitted from incomplete combustion can result in significant impacts on air quality and climate. Understanding the mixing state of ambient BC and the chemical characteristics of its associated coatings is particularly important to evaluate BC fate and environmental impacts. In this study, we investigate the formation of organic coatings on BC particles in an urban environment (Fontana, California) under hot and dry conditions using a soot-particle aerosol mass spectrometer (SP-AMS). The SP-AMS was operated in a configuration that can exclusively detect refractory BC (rBC) particles and their coatings. Using the −log(NO x / NO y ) ratio as a proxy for photochemical age of air masses, substantial formation of secondary organic aerosol (SOA) coatings on rBC particles was observed due to active photochemistry in the afternoon, whereas primary organic aerosol (POA) components were strongly associated with rBC from fresh vehicular emissions in the morning rush hours. There is also evidence that cooking-related organic aerosols were externally mixed from rBC. Positive matrix factorization and elemental analysis illustrate that most of the observed SOA coatings were freshly formed, providing an opportunity to examine SOA coating formation on rBCs near vehicular emissions. Approximately 7-20 wt % of secondary organic and inorganic species were estimated to be internally mixed with rBC on average, implying that rBC is unlikely the major condensation sink of SOA in this study. Comparison of our results to a co-located standard high-resolution time-offlight aerosol mass spectrometer (HR-ToF-AMS) measurement suggests that at least a portion of SOA materials condensed on rBC surfaces were chemically different from oxygenated organic aerosol (OOA) particles that were externally mixed with rBC, although they could both be generated from local photochemistry.

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Predicting hygroscopic growth using single particle chemical composition estimates

et al. 2014

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Single particle mass spectral data, collected in Paris, France, have been used to predict hygroscopic growth at the single particle level. The mass fractions of black carbon, organic aerosol, ammonium, nitrate, and sulphate present in each particle were estimated using a combination of single particle mass spectrometer and bulk aerosol chemical composition measurements. The Zdanovskii-Stokes-Robinson (ZSR) approach was then applied to predict hygroscopic growth factors based on these mass fraction estimates. Smaller particles with high black carbon mass fractions and low inorganic ion mass fractions exhibited the lowest predicted growth factors, while larger particles with high inorganic ion mass fractions exhibited the highest growth factors. Growth factors were calculated for subsaturated relative humidity (90%) to enable comparison with hygroscopic tandem differential mobility analyzer measurements. Mean predicted and measured hygroscopic growth factors for 110, 165, and 265 nm particles were found to agree within 6%. Single particle-based ZSR hygroscopicity estimates offer an advantage over bulk aerosol composition-based hygroscopicity estimates by providing additional chemical mixing state information. External mixing can be determined for particles of a given diameter through examination of the predicted hygroscopic growth factor distributions. Using this approach, 110 nm and 265 nm particles were found to be predominantly internally mixed; however, external mixing of 165 nm particles was observed periodically when thinly coated and thickly coated black carbon particles were simultaneously detected. Single particle-resolved chemical information will be useful for modeling efforts aimed at constraining cloud condensation nuclei activity and hygroscopic growth.

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Ambient black carbon particle hygroscopic properties controlled by mixing state and composition

Cited by 181 publications

References 56 publications

Winter time hygroscopicity and volatility of ambient urban aerosol particles

Winter time hygroscopicity and volatility of ambient urban aerosol particles

Formation of secondary organic aerosol coating on black carbon particles near vehicular emissions

Predicting hygroscopic growth using single particle chemical composition estimates

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