scholarly journals Cloud condensation nuclei activity of CaCO<sub>3</sub> particles with oleic acid and malonic acid coatings

2018 ◽  
Vol 18 (10) ◽  
pp. 7345-7359 ◽  
Author(s):  
Mingjin Wang ◽  
Tong Zhu ◽  
Defeng Zhao ◽  
Florian Rubach ◽  
Andreas Wahner ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Malonic Acid ◽  
Volume Fraction ◽  
Cloud Condensation Nuclei ◽  
Water Soluble ◽  
Coating Process ◽  
Condensation Nuclei ◽  
Mineral Particles ◽  
Acid Coating ◽  
Ccn Activity

Abstract. Condensation of carboxylic acids on mineral particles leads to coatings and impacts the particles' potential to act as cloud condensation nuclei (CCN). To determine how the CCN activity of mineral particles is impacted by carboxylic acid coatings, the CCN activities of CaCO3 particles and CaCO3 particles with oleic acid and malonic acid coatings were compared in this study. The results revealed that small amounts of oleic acid coating (volume fraction (vf) ≤4.3 %) decreased the CCN activity of CaCO3 particles, while more oleic acid coating (vf ≥16 %) increased the CCN activity of CaCO3 particles. This phenomenon has not been reported before. In contrast, the CCN activity of CaCO3 particles coated with malonic acid increased with the thickness of the malonic acid coating (vf =0.4–40 %). Even the smallest amounts of malonic acid coating (vf =0.4 %) significantly enhanced the CCN activity of CaCO3 particles from κ=0.0028±0.0001 to κ=0.0123±0.0005. This indicates that a small amount of water-soluble organic acid coating may significantly enhance the CCN activity of mineral particles. The presence of water vapor during the coating process with malonic acid additionally increased the CCN activity of the coated CaCO3 particles, probably because more CaCO3 reacts with malonic acid when sufficient water is available.

scholarly journals Cloud Condensation Nuclei Activity of CaCO<sub>3</sub> Particles with Oleic Acid and Malonic Acid Coatings

2017 ◽  
Author(s):  
Mingjin Wang ◽  
Tong Zhu ◽  
Defeng Zhao ◽  
Florian Rubach ◽  
Andreas Wahner ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Relative Humidity ◽  
Malonic Acid ◽  
Volume Fraction ◽  
Cloud Condensation Nuclei ◽  
Water Soluble ◽  
Condensation Nuclei ◽  
Mineral Particles ◽  
Acid Coating ◽  
Ccn Activity

Abstract. Condensation of carboxylic acids on mineral particles will lead to coatings, and impact on the particles' potential to act as cloud condensation nuclei (CCN). To determine how the CCN activity of mineral particles is impacted by carboxylic acid coatings, the CCN activity of CaCO3 particles and CaCO3 particles with oleic acid and malonic acid coatings were compared in this study. The results revealed that small amounts of oleic acid coating (volume fraction (vf) ≤ 4.1 %) decreased the CCN activity of CaCO3 particles, while more oleic acid coating (vf ≥ 14.8 %) increased the CCN activity of CaCO3 particles. This phenomenon has not been reported before. On the other hand, malonic acid coating (vf = 0.4–42 %) increased the CCN activity of CaCO3 particles regardless of the amount of the coating. The CCN activity of CaCO3 particles with malonic acid coating increased with the amount of malonic acid coating. Even smallest amounts of malonic acid coating (vf = 0.4 %) significantly enhanced the CCN activity of CaCO3 particles from κ = 0.0028 ± 0.0001 to κ = 0.0123 ± 0.0005. This supports that a small amount of water-soluble organic acid coating may significantly enhance the CCN activity of mineral particles. The presence of about 50 % relative humidity during the coating process with malonic acid additionally increased the CCN activity of the coated CaCO3 particles, probably because more CaCO3 reacts with malonic acid at higher relative humidity.

scholarly journals Cloud condensation nuclei measurements in the marine boundary layer of the Eastern Mediterranean: CCN closure and droplet growth kinetics

2009 ◽  
Vol 9 (18) ◽  
pp. 7053-7066 ◽  
Author(s):  
A. Bougiatioti ◽  
C. Fountoukis ◽  
N. Kalivitis ◽  
S. N. Pandis ◽  
A. Nenes ◽  
...  
Keyword(s):  
Size Distribution ◽  
Growth Kinetics ◽  
Eastern Mediterranean ◽  
Cloud Condensation Nuclei ◽  
Bulk Composition ◽  
Organic Content ◽  
Water Soluble ◽  
Aerosol Size Distribution ◽  
Droplet Growth ◽  
Condensation Nuclei

Abstract. Measurements of cloud condensation nuclei (CCN) concentrations (cm−3) between 0.2 and 1.0% supersaturation, aerosol size distribution and chemical composition were performed at a remote marine site in the eastern Mediterranean, from September to October 2007 during the FAME07 campaign. Most of the particles activate at ~0.6% supersaturation, characteristic of the aged nature of the aerosol sampled. Application of Köhler theory, using measurements of bulk composition, size distribution, and assuming that organics are insoluble resulted in agreement between predicted and measured CCN concentrations within 7±11% for all supersaturations, with a tendency for CCN underprediction (16±6%; r2=0.88) at the lowest supersaturations (0.21%). Including the effects of the water-soluble organic fraction (which represent around 70% of the total organic content) reduces the average underprediction bias at the low supersaturations, resulting in a total closure error of 0.6±6%. Using threshold droplet growth analysis, the growth kinetics of ambient CCN is consistent with NaCl calibration experiments; hence the presence of aged organics does not suppress the rate of water uptake in this environment. The knowledge of the soluble salt fraction is sufficient for the description of the CCN activity in this area.

scholarly journals Analysis of CCN activity of Arctic aerosol and Canadian biomass burning during summer 2008

2013 ◽  
Vol 13 (5) ◽  
pp. 2735-2756 ◽  
Author(s):  
T. L. Lathem ◽  
A. J. Beyersdorf ◽  
K. L. Thornhill ◽  
E. L. Winstead ◽  
M. J. Cubison ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Biomass Burning ◽  
Industrial Pollution ◽  
Physical Aging ◽  
Volume Fraction ◽  
Cloud Condensation Nuclei ◽  
Water Soluble ◽  
The Arctic ◽  
High Concentration ◽  
Air Masses

Abstract. The NASA DC-8 aircraft characterized the aerosol properties, chemical composition, and cloud condensation nuclei (CCN) concentrations of the summertime Arctic during the 2008 NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. Air masses characteristic of fresh and aged biomass burning, boreal forest, Arctic background, and anthropogenic industrial pollution were sampled. Observations were spatially extensive (50–85° N and 40–130° W) and exhibit significant variability in aerosol and CCN concentrations. The chemical composition was dominated by highly oxidized organics (66–94% by volume), with a water-soluble mass fraction of more than 50%. The aerosol hygroscopicity parameter, κ, ranged between κ = 0.08–0.32 for all air mass types. Industrial pollution had the lowest κ of 0.08 ± 0.01, while the Arctic background had the highest and most variable κ of 0.32 ± 0.21, resulting from a lower and more variable organic fraction. Both fresh and aged (long-range transported) biomass burning air masses exhibited remarkably similar κ (0.18 ± 0.13), consistent with observed rapid chemical and physical aging of smoke emissions in the atmosphere, even in the vicinity of fresh fires. The organic hygroscopicity (κorg) was parameterized by the volume fraction of water-soluble organic matter (εWSOM), with a κ = 0.12, such that κorg = 0.12εWSOM. Assuming bulk (size-independent) composition and including the κorg parameterization enabled CCN predictions to within 30% accuracy for nearly all environments sampled. The only exception was for industrial pollution from Canadian oil sands exploration, where an external mixture and size-dependent composition was required. Aerosol mixing state assumptions (internal vs. external) in all other environments did not significantly affect CCN predictions; however, the external mixing assumption provided the best results, even though the available observations could not determine the true degree of external mixing and therefore may not always be representative of the environments sampled. No correlation was observed between κorg and O : C. A novel correction of the CCN instrument supersaturation for water vapor depletion, resulting from high concentrations of CCN, was also employed. This correction was especially important for fresh biomass burning plumes where concentrations exceeded 1.5×104 cm−3 and introduced supersaturation depletions of &amp;geq;25%. Not accounting for supersaturation depletion in these high concentration environments would therefore bias CCN closure up to 25% and inferred κ by up to 50%.

scholarly journals Droplet activation of wet particles: development of the Wet CCN approach

2014 ◽  
Vol 7 (1) ◽  
pp. 257-292
Author(s):  
S. Nakao ◽  
S. R. Suda ◽  
M. Camp ◽  
M. D. Petters ◽  
S. M. Kreidenweis
Keyword(s):  
Experimental Approach ◽  
Cloud Condensation Nuclei ◽  
Ammonium Oxalate ◽  
Water Soluble ◽  
Spherical Particles ◽  
Primary Means ◽  
Wet Particles ◽  
Physical And Chemical ◽  
The Impact ◽  
Ccn Activity

Abstract. Relationships between critical supersaturation required for activation and particle dry diameter have been the primary means for experimentally characterizing cloud condensation nuclei (CCN) activity; however, use of the dry diameter inherently limits the application to cases where the dry diameter can be used to accurately estimate solute volume. This study challenges the requirement and proposes a new experimental approach, Wet CCN, for studying CCN activity without the need for a drying step. The new approach directly measures Köhler curves under sub-saturated conditions. The experimental setup consists of a humidity-controlled differential mobility analyzer and a CCN counter; wet diameter equilibrated at known relative humidity is used to characterize CCN activity instead of the dry diameter. The experimental approach was validated against ammonium sulfate, glucose and non-spherical ammonium oxalate monohydrate. Further, the approach was applied to a mixture of non-spherical iodine oxide particles. The Wet CCN approach successfully determined the hygroscopicity of non-spherical particles by collapsing them into spherical, deliquesced droplets. We further show that the Wet CCN approach offers unique insights to the physical and chemical impacts of the aqueous phase on CCN activity; a potential application is to investigate the impact of evaporation/co-condensation of water-soluble semi-volatile species on CCN activity.

scholarly journals Impact of aerosol composition on cloud condensation nuclei activity

2012 ◽  
Vol 12 (8) ◽  
pp. 3783-3790 ◽  
Author(s):  
Q. Zhang ◽  
J. Meng ◽  
J. Quan ◽  
Y. Gao ◽  
D. Zhao ◽  
...  
Keyword(s):  
Size Distribution ◽  
Field Experiments ◽  
Cloud Condensation Nuclei ◽  
Diffusion Chamber ◽  
Aerosol Size Distribution ◽  
Condensation Nuclei ◽  
Aerosol Composition ◽  
Rate Of Increase ◽  
The Impact ◽  
Ccn Activity

Abstract. The impact of aerosol composition on cloud condensation nuclei (CCN) activity were analyzed in this study based on field experiments carried out at downtown Tianjin, China in September 2010. In the experiments, the CCN measurements were performed at supersaturation (SS) of 0.1%, 0.2% and 0.4% using a thermal-gradient diffusion chamber (DMT CCNC), whereas the aerosol size distribution and composition were simultaneously measured with a TSI SMPS and an Aerodyne Aerosol Mass Spectrometer (AMS), respectively. The results show that the influence of aerosol composition on CCN activity is notable under low SS (0.1%), and their influence decreased with increasing SS. For example, under SS of 0.1%, the CCN activity increases from 4.5±2.6% to 12.8±6.1% when organics fraction decrease from 30–40% to 10–20%. The rate of increase reached up to 184%. While under SS of 0.4%, the CCN activity increases only from 35.7±19.0% to 46.5±12.3% correspondingly. The calculated NCCN based on the size-resolved activation ratio and aerosol number size distribution correlated well with observed NCCN at high SS (0.4%), but this consistence decreased with the falling of SS. The slopes of linear fitted lines between calculated and observed NCCN are 0.708, 0.947, and 0.995 at SS of 0.1%, 0.2% and 0.4% respectively. Moreover, the stand deviation (SD) of calculated NCCN increased with the decreasing of SS. A case study of CCN closure analyses indicated that the calculated error of NCCN could reach up to 34% at SS of 0.1% if aerosol composition were not included, and the calculated error decreased with the raising of SS. It is decreased to 9% at SS of 0.2%, and further decreased to 4% at SS of 0.4%.

scholarly journals Cloud droplet activation of black carbon particles coated with organic compounds of varying solubility

2018 ◽  
Vol 18 (16) ◽  
pp. 12477-12489 ◽  
Author(s):  
Maryam Dalirian ◽  
Arttu Ylisirniö ◽  
Angela Buchholz ◽  
Daniel Schlesinger ◽  
Johan Ström ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Black Carbon ◽  
Glutaric Acid ◽  
Theoretical Calculations ◽  
Water Soluble ◽  
Climate Effect ◽  
Organic Species ◽  
Surprising Effect ◽  
Study Laboratory ◽  
Ccn Activity

Abstract. Atmospheric black carbon (BC) particles are a concern due to their impact on air quality and climate. Their net climate effect is, however, still uncertain. This uncertainty is partly related to the contribution of coated BC particles to the global cloud condensation nuclei (CCN) budgets. In this study, laboratory measurements were performed to investigate CCN activity of BC (REGAL 400R pigment black) particles, in pure state or coated through evaporating and subsequent condensation of glutaric acid, levoglucosan (both water-soluble organics) or oleic acid (an organic compound with low solubility). A combination of soot particle aerosol mass spectrometer (SP-AMS) measurements and size distribution measurements with a scanning mobility particle sizer (SMPS) showed that the studied BC particles were nearly spherical agglomerates with a fractal dimension of 2.79 and that they were coated evenly by the organic species. The CCN activity of BC particles increased after coating with all the studied compounds and was governed by the fraction of organic material. The CCN activation of the BC particles coated by glutaric acid and levoglucosan were in good agreement with the theoretical calculations using the shell-and-core model, which is based on a combination of the CCN activities of the pure compounds. The oleic acid coating enhanced the CCN activity of the BC particles, even though the pure oleic acid particles were CCN inactive. The surprising effect of oleic acid might be related to the arrangement of the oleic acid molecules on the surface of the BC cores or other surface phenomena facilitating water condensation onto the coated particles. Our results show that present theories have potential for accurately predicting the CCN activity of atmospheric BC coated with organic species, given that the identities and amounts of the coating species are known. Furthermore, our results suggest that even relatively thin soluble coatings (around 2 nm for the compounds studied here) are enough to make the insoluble BC particles CCN active at typical atmospheric supersaturations and thus be efficiently taken up by cloud droplets. This highlights the need for an accurate description of the composition of atmospheric particles containing BC to unravel their net impact on climate.

scholarly journals Impact of isolated atmospheric aging processes on the cloud condensation nuclei activation of soot particles

2019 ◽  
Vol 19 (24) ◽  
pp. 15545-15567 ◽  
Author(s):  
Franz Friebel ◽  
Prem Lobo ◽  
David Neubauer ◽  
Ulrike Lohmann ◽  
Saskia Drossaart van Dusseldorp ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Climate Model ◽  
Cloud Condensation Nuclei ◽  
Particle Diameter ◽  
Cloud Droplet ◽  
High Sensitivity ◽  
Condensation Nuclei ◽  
Soot Particles ◽  
Atmospheric Aging ◽  
Ccn Activity

Abstract. The largest contributors to the uncertainty in assessing the anthropogenic contribution in radiative forcing are the direct and indirect effects of aerosol particles on the Earth's radiative budget. Soot particles are of special interest since their properties can change significantly due to aging processes once they are emitted into the atmosphere. Probably the largest obstacle for the investigation of these processes in the laboratory is the long atmospheric lifetime of 1 week, requiring tailored experiments that cover this time span. This work presents results on the ability of two types of soot, obtained using a miniCAST soot generator, to act as cloud condensation nuclei (CCN) after exposure to atmospherically relevant levels of ozone (O3) and humidity. Aging times of up to 12 h were achieved by successful application of the continuous-flow stirred tank reactor (CSTR) concept while allowing for size selection of particles prior to the aging step. Particles of 100 nm diameter and rich in organic carbon (OC) that were initially CCN inactive showed significant CCN activity at supersaturations (SS) down to 0.3 % after 10 h of exposure to 200 ppb of O3. While this process was not affected by different levels of relative humidity in the range of 5 %–75 %, a high sensitivity towards the ambient/reaction temperature was observed. Soot particles with a lower OC content required an approximately 4-fold longer aging duration to show CCN activity at the same SS. Prior to the slow change in the CCN activity, a rapid increase in the particle diameter was detected which occurred within several minutes. This study highlights the applicability of the CSTR approach for the simulation of atmospheric aging processes, as aging durations beyond 12 h can be achieved in comparably small aerosol chamber volumes (<3 m3). Implementation of our measurement results in a global aerosol-climate model, ECHAM6.3-HAM2.3, showed a statistically significant increase in the regional and global CCN burden and cloud droplet number concentration.

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