Impacts of Cloud‐Processing on Ice Nucleation of Soot Particles Internally Mixed With Sulfate and Organics

Gao, Kunfeng; Kanji, Zamin A.

doi:10.1029/2022jd037146

Cited by 8 publications

(4 citation statements)

References 114 publications

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“…It is therefore possible that aromatics may also facilitate freezing of fresh soot particles. Organics and sulfuric acid in the particle phase can have a large influence on the IN ability of soot particles, for example, by filling pores and thus, inhibiting pore condensation freezing, or by increasing particles' hygroscopicities due to sulfuric acid coatings (Gao & Kanji, 2022).…”

Section: In Activitymentioning

confidence: 99%

Marine Fuel Regulations and Engine Emissions: Impacts on Physicochemical Properties, Cloud Activity and Emission Factors

Santos,

Salo,

Kong

et al. 2024

JGR Atmospheres

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Marine regulations aim to reduce sulfur and nitrogen exhaust emissions from maritime shipping. Here, two compliance pathways for reducing sulfur dioxide emissions, fuel sulfur content reduction and exhaust wet scrubbing, are studied for their effects on physicochemical properties and cloud forming abilities of engine exhaust particles. A test‐bed diesel engine was utilized to study fresh exhaust emissions from combustion of non‐compliant, high sulfur content fuel with (WS) and without (HiS) the usage of a wet scrubber as well as a regulatory compliant, low sulfur content fuel (LoS). Particle number emissions are decreased by ≈99% when switching to LoS due to absence of 20–30 nm sulfate rich particles. While number emissions for WS are also decreased, a shift in the sulfate mode toward larger sizes was found to increase particle mass emission factors by at least 31%. Changes in the mixing state induced by the compliance measures are reflected in the hygroscopicity of the exhaust particles. Fuel sulfur reduction decreased cloud condensation nuclei emissions by at least 97% due to emissions of primarily hydrophobic soot particles. Wet scrubbing increased those emissions, mainly driven by changes in particle size distributions. Our results indicate that both compliance alternatives have no obvious impact on the ice forming abilities of 200 nm exhaust particles. These detailed results are relevant for atmospheric processes and might be useful input parameters for cloud‐resolving models to investigate ship aerosol‐cloud interactions and to quantify the impact of shipping on radiative budgets from local to global scales.

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Section: In Activitymentioning

confidence: 99%

Marine Fuel Regulations and Engine Emissions: Impacts on Physicochemical Properties, Cloud Activity and Emission Factors

Santos,

Salo,

Kong

et al. 2024

JGR Atmospheres

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“…Laboratory studies have shown that coating of particles may reduce or inhibit their ice nucleation at cirrus temperatures, depending on the composition and thickness of the coating (Cziczo et al, 2009;Gao & Kanji, 2022b;Koehler et al, 2010;Möhler et al, 2008;Primm et al, 2017). When particles form ice via PCF, coatings should hamper ice nucleation when they block pores, as measured in the case of soot (Gao & Kanji, 2022a). Yet, a thin coating may even facilitate water condensation and ice growth in case of wider pores or when the adsorbed material renders the particle surface more hydrophilic (Marcolli, 2017;Marcolli et al, 2021).…”

Section: Ice Activities Of Mineral Dust and Aviation Sootmentioning

confidence: 99%

The Role of Mineral Dust Aerosol Particles in Aviation Soot‐Cirrus Interactions

Kärcher¹,

Marcolli

Mahrt

2023

JGR Atmospheres

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Predicting cirrus cloud properties with confidence requires a sound understanding of the relative roles of homogeneous and heterogeneous ice formation. This study explores the effect of mineral dust and contrail‐processed aviation soot particles as ice‐nucleating particles (INPs) competing with liquid solution droplets in cirrus formation. We study aerosol‐cirrus interactions by accounting for atmospheric variability in updraft speeds and INP number concentrations. Our results confirm the dominant role of mineral dust in ice nucleation events in cirrus clouds. In addition, we show that pre‐existing thin cirrus may suppress ice formation when updraft speeds are low. We find that homogeneous freezing of liquid solution droplets dominates clear‐sky aerosol‐cirrus interaction above a threshold updraft speed determined by total number concentrations and ice nucleation abilities of INPs. When mineral dust particles exceed number concentrations of 10 L−1, they reduce homogeneously nucleated ice crystal numbers significantly and even prevent homogeneous freezing for frequently observed local updraft speeds between 10 and 20 cm s−1. When both mineral dust and aviation soot particles coexist with solution droplets, dust typically prevents ice nucleation by aviation soot. Aviation soot exerts a notable impact on cirrus ice numbers only if updrafts are weak, large soot particles are present in number concentrations that are considerably higher than typically observed in emission measurements, and/or number concentrations of mineral dust and other INPs are low. Overall, our results elucidate the role of aviation soot‐cirrus interactions in the presence of other INP types.

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“…According to the Kelvin equation, wettable soot particles ( θ < 90°) are needed to promote capillary condensation, followed by freezing below the homogeneous nucleation temperature (HNT). Soot particles of higher porosity and surface wettability were reported to be more active INPs (Mahrt et al., 2018; Nichman et al., 2019) and after increasing the porosity of soot particles by compaction or removing organics, ice nucleation by PCF is enhanced (Gao, Friebel, et al., 2022; Gao & Kanji, 2022a, 2022b; Gao, Koch, et al., 2022; Mahrt et al., 2020; Testa et al., 2024). The results also suggest that PCF of an organic‐lean soot (PR90) might be limited by its insufficient surface wettability (Gao, Friebel, et al., 2022).…”

Section: Introductionmentioning

confidence: 99%

Influence of Lowering Soot‐Water Contact Angle on Ice Nucleation of Ozone‐Aged Soot

Gao,

Kanji

2024

Geophysical Research Letters

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Organic‐lean and organic‐rich size‐selected soot particles were exposed to a varying O3 concentration, progressively decreasing the soot‐water contact angle (θ) to study its impact on ice nucleation (IN). The IN ability of fresh and O3‐aged soot between 218 and 233 K was observed while monitoring the particle mass and size distributions. The properties of fresh and O3‐aged bulk organic‐lean soot samples with a low and high O3‐adsorption were characterized for soot‐water θ, chemical composition, functional groups, soot‐water interaction ability and porosity. By retaining the soot porosity between aged and unaged samples, we demonstrate that a decrease in θ after O3‐aging enhances organic‐lean soot IN via pore condensation and freezing. Fresh organic‐rich soot exhibits suppressed homogeneous freezing, but after O3‐aging it freezes within uncertainty of the homogeneous freezing threshold of solution drops, because of increased hydrophilicity.

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Impacts of Cloud‐Processing on Ice Nucleation of Soot Particles Internally Mixed With Sulfate and Organics

Abstract: Soot particles, also known as black carbon particles, are characterized as one of the strongest anthropogenic radiative forcers on Earth, exhibiting a net-warming effect on climate (

Cited by 8 publications

References 114 publications

Marine Fuel Regulations and Engine Emissions: Impacts on Physicochemical Properties, Cloud Activity and Emission Factors

Marine Fuel Regulations and Engine Emissions: Impacts on Physicochemical Properties, Cloud Activity and Emission Factors

The Role of Mineral Dust Aerosol Particles in Aviation Soot‐Cirrus Interactions

Influence of Lowering Soot‐Water Contact Angle on Ice Nucleation of Ozone‐Aged Soot

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