Hygroscopic growth and droplet activation of soot particles: uncoated, succinic or sulfuric acid coated

Henning, S.; Ziese, Markus; Kiselev, Alexei; Saathoff, H.; Möhler, Ottmar; Mentel, Thomas F.; Buchholz, Angela; Spindler, C.; Michaud, V.; Monier, Marie; Sellegri, Karine; Stratmann, Frank

doi:10.5194/acp-12-4525-2012

Cited by 62 publications

(48 citation statements)

References 58 publications

(66 reference statements)

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“…These results are consistent with past studies that failed to find sub-saturated hygroscopic growth or supersaturated CCN activation (s ≤ 1%) for uncoated Mini-CAST soot (Friedman et al 2011;Henning et al 2012). Popovicheva et al (2008) used a gravimetric method to measure sub-saturated water uptake on CAST burner soot at two conditions: flame C/O ratio of 0.29 (4% OC) and 0.4 (27% OC), which are the same conditions examined by Möhler et al (2005).…”

Section: Soot Hygroscopicitysupporting

confidence: 79%

“…Operation is safe, stable, and capable of generating high concentrations of soot (Jing 1999). Consequently, a large number of studies have used the Mini-CAST (or a similar, larger CAST) burner to study coated or uncoated soot in terms of optical properties, ice nucleation, and cloud droplet nucleation (Möhler et al 2005;Schnaiter et al 2006;Crawford et al 2011;Henning et al 2012). Typically, a few burner conditions are used to create soot of varying OC:EC ratios, which are well characterized.…”

Section: Introductionmentioning

confidence: 99%

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Mapping the Operation of the Miniature Combustion Aerosol Standard (Mini-CAST) Soot Generator

Moore

Ziemba

Dutcher

et al. 2014

Aerosol Science and Technology

107

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The Jing Ltd. miniature combustion aerosol standard (Mini-CAST) soot generator is a portable, commercially available burner that is widely used for laboratory measurements of soot processes. While many studies have used the Mini-CAST to generate soot with known size, concentration, and organic carbon fraction under a single or few conditions, there has been no systematic study of the burner operation over a wide range of operating conditions. Here, we present a comprehensive characterization of the microphysical, chemical, morphological, and hygroscopic properties of Mini-CAST soot over the full range of oxidation air and mixing N 2 flow rates. Very fuel-rich and fuel-lean flame conditions are found to produce organic-dominated soot with mode diameters of 10-60 nm, and the highest particle number concentrations are produced under fuel-rich conditions. The lowest organic fraction and largest diameter soot (70-130 nm) occur under slightly fuel-lean conditions. Moving from fuel-rich to fuel-lean conditions also increases the O:C ratio of the soot coatings from ∼0.05 to ∼0.25, which causes a small fraction of the particles to act as cloud condensation nuclei near the Kelvin limit (κ ∼ 0-10 −3 ). Comparison of these property ranges to those reported in the literature for aircraft and diesel engine soots indicates that the Mini-CAST soot is similar to real-world primary soot particles, which lends itself to a variety of process-based soot studies. The trends in soot properties uncovered here will guide selection of burner operating conditions to achieve optimum soot properties that are most relevant to such studies.

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Section: Soot Hygroscopicitysupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Mapping the Operation of the Miniature Combustion Aerosol Standard (Mini-CAST) Soot Generator

Moore

Ziemba

Dutcher

et al. 2014

Aerosol Science and Technology

107

View full text Add to dashboard Cite

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“…The cloud forming properties of soot can be altered, and climate forcing can be influenced (albeit indirectly), by coating the soot with soluble material. For example, atmospheric ageing of coated soot enhances the hygroscopicity of the coatings and, hence, aged soot particles can act as efficient cloud condensation nuclei (CCN) or ice nuclei (IN) (Ammann et al, 1998;Henning et al, 2012). Transformation from fresh hydrophobic soot to processed hygroscopic soot can also have adverse health effects as, compared with hydrophobic fresh soot, aged hygroscopic soot has an altered deposition in the lungs (Löndahl et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Morphological transformation of soot: investigation of microphysical processes during the condensation of sulfuric acid and limonene ozonolysis product vapors

et al. 2018

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Abstract. The morphological transformation of soot particles via condensation of low-volatility materials constitutes a dominant atmospheric process with serious implications for the optical and hygroscopic properties, as well as atmospheric lifetime of the soot. We consider the morphological transformation of soot aggregates under the influence of condensation of vapors of sulfuric acid, and/or limonene ozonolysis products. This influence was systematically investigated using a Differential Mobility Analyzer coupled with an Aerosol Particle Mass Analyzer (DMA-APM) and the Tandem DMA techniques integrated with a laminar flowtube system. We hypothesize that the morphology transformation of soot results (in general) from a two-step process, i.e., (i) filling of void space within the aggregate and (ii) growth of the particle diameter. Initially, the transformation was dominated by the filling process followed by growth, which led to the accumulation of sufficient material that exerted surface forces, which eventually facilitated further filling. The filling of void space was constrained by the initial morphology of the fresh soot as well as the nature and the amount of condensed material. This process continued in several sequential steps until all void space within the soot aggregate was filled. And then "growth" of a spherical particle continued as long as vapors condensed on it. We developed a framework for quantifying the microphysical transformation of soot upon the condensation of various materials. This framework used experimental data and the hypothesis of "ideal sphere growth" and void filling to quantify the distribution of condensed materials in the complementary filling and growth processes. Using this framework, we quantified the percentage of material consumed by these processes at each step of the transformation. For the largest coating experiments, 6, 10, 24, and 58 % of condensed material went to filling process, while 94, 90, 76, and 42 % of condensed material went to growth process for 75, 100, 150, and 200 nm soot particles, respectively. We also used the framework to estimate the fraction of internal voids and open voids. This information was then used to estimate the volume-equivalent diameter of the soot aggregate containing internal voids and to calculate the dynamic shape factor, accounting for internal voids. The dynamic shape factor estimated based on the traditional assumption (of no internal voids) differed significantly from the value obtained in this study. Internal voids are accounted for in the experimentally derived dynamic shape factor determined in the present study. In fact, the dynamic shape factor adjusted for internal voids was close to 1 for the fresh soot particles considered in this study, indicating the particles were largely spherical. The effective density was strongly correlated with the morphological transformation responses to the condensed material on the soot particle, and the resultant effective density was determined by the (i) nature of the condensed material an...

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“…The interaction also included hygroscopic shrinkage. Hygroscopic GFs up to 1.11 were obtained with succinic acid at 98% RH for particles with 375 and 500 nm dry diameter (Henning et al, 2012). It has to be noted that succinic acid coating on soot particles appears to be a good example for oxygenated organic substances in atmospheric environments strongly influenced by biogenic activities, while the situation with the coatings in urban environments can be different.…”

mentioning

confidence: 99%

“…The tendencies in the hygroscopic and volatile properties, and in the particle number fraction of modes mentioned above are ordinarily observed in urban VH-TDMA studies (e.g., Ferron et al, 2005) since the particle number size distribution of soot from traffic emissions peaks between 50 and 100 nm (Weingartner et al, 1997). It was previously concluded that uncoated fresh soot particles (although of somewhat larger diameters than 145 nm) showed neither hygroscopic growth nor water activation, while their coating with succinic acid, sulphuric acid or polyaromatic hydrocarbons (PAHs) influenced the hygroscopic growth in a complex way (Henning et al, 2012). The diameter change depended on the amount and type of the coatings, on the "humidity history" of particles (coating 5 by solution layer or solid film) and on the carrier gas used in the experiments.…”

mentioning

confidence: 99%

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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Hygroscopic growth and droplet activation of soot particles: uncoated, succinic or sulfuric acid coated

Abstract: Abstract. The hygroscopic growth and droplet activation of uncoated soot particles and such coated with succinic acid and sulfuric acid were investigated during the IN-11 cam-

Cited by 62 publications

References 58 publications

Mapping the Operation of the Miniature Combustion Aerosol Standard (Mini-CAST) Soot Generator

Mapping the Operation of the Miniature Combustion Aerosol Standard (Mini-CAST) Soot Generator

Morphological transformation of soot: investigation of microphysical processes during the condensation of sulfuric acid and limonene ozonolysis product vapors

Winter time hygroscopicity and volatility of ambient urban aerosol particles

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