Studies of propane flame soot acting as heterogeneous ice nuclei in conjunction with single particle soot photometer measurements

Crawford, Ian; Möhler, Ottmar; Schnaiter, M.; Saathoff, H.; Liu, Dantong; McMeeking, G. R.; Linke, Christian; Flynn, Michael J.; Bower, Keith; Connolly, Paul; Gallagher, Martin; Coe, Hugh

doi:10.5194/acp-11-9549-2011

Cited by 69 publications

(102 citation statements)

References 58 publications

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“…with respect to their organic carbon content, depending on the combustible and the combustion technique. Möhler et al (2005b) and Crawford et al (2011) found a significant decrease in ice nucleation activity with increasing organic carbon content at temperatures around −65 • C and −47 • C, respectively. However, no systematic trends related to the soot type are seen from the experiments at higher temperatures.…”

Section: Sootmentioning

confidence: 99%

Heterogeneous ice nucleation on atmospheric aerosols: a review of results from laboratory experiments

2012

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Abstract.A small subset of the atmospheric aerosol population has the ability to induce ice formation at conditions under which ice would not form without them (heterogeneous ice nucleation). While no closed theoretical description of this process and the requirements for good ice nuclei is available, numerous studies have attempted to quantify the ice nucleation ability of different particles empirically in laboratory experiments. In this article, an overview of these results is provided. Ice nucleation "onset" conditions for various mineral dust, soot, biological, organic and ammonium sulfate particles are summarized. Typical temperaturesupersaturation regions can be identified for the "onset" of ice nucleation of these different particle types, but the various particle sizes and activated fractions reported in different studies have to be taken into account when comparing results obtained with different methodologies. When intercomparing only data obtained under the same conditions, it is found that dust mineralogy is not a consistent predictor of higher or lower ice nucleation ability. However, the broad majority of studies agrees on a reduction of deposition nucleation by various coatings on mineral dust. The ice nucleation active surface site (INAS) density is discussed as a simple and empirical normalized measure for ice nucleation activity. For most immersion and condensation freezing measurements on mineral dust, estimates of the temperature-dependent INAS density agree within about two orders of magnitude. For deposition nucleation on dust, the spread is significantly larger, but a general trend of increasing INAS densities with increasing supersaturation is found. For soot, the presently available results are divergent. Estimated average INAS densities are high for ice-nucleation active bacteria at high subzero temperatures. At the same time, it is shown that INAS densities of some other biological aerosols, like certain pollen grains, fungal spores and diatoms, tend to be similar to those of dust. These particles may owe their high ice nucleation onsets to their large sizes. Surface-area-dependent parameterizations of heterogeneous ice nucleation are discussed. For immersion freezing on mineral dust, fitted INAS densities are available, but should not be used outside the temperature interval of the data they were based on. Classical nucleation theory, if employed with only one fitted contact angle, does not reproduce the observed temperature dependence for immersion nucleation, the temperature and supersaturation dependence for deposition nucleation, and the time dependence of ice nucleation. Formulations of classical nucleation theory with distributions of contact angles offer possibilities to overcome these weaknesses.

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Section: Sootmentioning

confidence: 99%

Heterogeneous ice nucleation on atmospheric aerosols: a review of results from laboratory experiments

2012

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“…Consequently, the size modes and concentrations reported here may differ from results obtained with other experimental setups. This is particularly true for studies that employ a stagnation chamber to enhance coagulation and grow the soot agglomerates to large sizes (Schnaiter et al 2006;Crawford et al 2011). Schnaiter et al (2006) characterized a CAST burner and observed modal diameters of 300-340 nm for Q mix = 0.0 L min −1 and flame C:O ∼0.25-0.29.…”

Section: Soot Size and Concentrationmentioning

confidence: 99%

“…However, since the soot mode size and OC/TC both seem to scale with Q oxi (i.e., flame C:O ratio) and Q mix (Figure 4b), OC/TC collapses neatly into a monotonic curve when plotted versus soot modal size (Figure 4a). Since we neglect the influence of particle coagulation on the soot modal diameter, this relationship may not hold under conditions where coagulation processes significantly alter the soot size distribution (e.g., when using a mixing volume as in Crawford et al 2011). Consequently, relationships based on Q oxi and Q mix should be used.…”

Section: Soot Chemical Compositionmentioning

confidence: 99%

“…They observe the same bimodal size distribution reported here in Figure 2, and attribute the increased OC fraction to the presence of these nucleation mode particles. Crawford et al (2011) extended the CAST data of Schnaiter et al (2006) by looking at the OC fraction of Mini-CAST soot under similar conditions. They find a shift in OC/TC compared with the CAST burner, with OC fractions of ∼30% and ∼70%-80% (2013) report OC/TC ratios for both denuded and undenuded Mini-CAST 5200 soot, and find an undenuded soot organic fraction of ∼77% for C:O = 0.44 (Q oxi = 1.00 L min −1 and Q mix = 0.00 L min −1 ), which is higher than in the present study (SI).…”

Section: Soot Chemical Compositionmentioning

confidence: 99%

“…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%

See 2 more Smart Citations

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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Ice nucleation activity of diesel soot particles at cirrus relevant temperature conditions: Effects of hydration, secondary organics coating, soot morphology, and coagulation

Kulkarni

China

Liu

et al. 2016

Geophysical Research Letters

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Ice formation by diesel soot particles was investigated at temperatures ranging from −40 to −50°C. Size‐selected soot particles were physically and chemically aged in an environmental chamber, and their ice nucleating properties were determined using a continuous flow diffusion type ice nucleation chamber. Bare (freshly formed), hydrated, and compacted soot particles, as well as α‐pinene secondary organic aerosol (SOA)‐coated soot particles at high relative humidity conditions, showed ice formation activity at subsaturation conditions with respect to water but below the homogeneous freezing threshold conditions. However, SOA‐coated soot particles at dry conditions were observed to freeze at homogeneous freezing threshold conditions. Overall, our results suggest that heterogeneous ice nucleation activity of freshly emitted diesel soot particles are sensitive to some of the aging processes that soot can undergo in the atmosphere.

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Studies of propane flame soot acting as heterogeneous ice nuclei in conjunction with single particle soot photometer measurements

Cited by 69 publications

References 58 publications

Heterogeneous ice nucleation on atmospheric aerosols: a review of results from laboratory experiments

Heterogeneous ice nucleation on atmospheric aerosols: a review of results from laboratory experiments

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

Ice nucleation activity of diesel soot particles at cirrus relevant temperature conditions: Effects of hydration, secondary organics coating, soot morphology, and coagulation

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