Investigation of cloud condensation nuclei properties and droplet growth kinetics of the water-soluble aerosol fraction in Mexico City

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.

Download Full-text

Cloud condensation nuclei droplet growth kinetics of ultrafine particles during anthropogenic nucleation events

Atmospheric Environment ◽

10.1016/j.atmosenv.2011.10.049 ◽

2012 ◽

Vol 47 ◽

pp. 389-398 ◽

Cited By ~ 8

Author(s):

N.C. Shantz ◽

J.R. Pierce ◽

R.Y.-W. Chang ◽

A. Vlasenko ◽

I. Riipinen ◽

...

Keyword(s):

Growth Kinetics ◽

Ultrafine Particles ◽

Cloud Condensation Nuclei ◽

Droplet Growth ◽

Condensation Nuclei ◽

Kinetics Of

Download Full-text

Cloud condensation nuclei measurements in the eastern Mediterranean marine boundary layer: CCN closure and droplet growth kinetics

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-10303-2009 ◽

2009 ◽

Vol 9 (2) ◽

pp. 10303-10336 ◽

Cited By ~ 5

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 FAME-07 campaign. Virtually all the particles activate at 0.8% supersaturation, consistent with the very aged nature of the aerosol sampled. Application of Köhler theory, using measurements of bulk composition and size distribution, and assuming that organics are insoluble resulted in agreement between predicted and measured CCN concentrations within 3.4±11% for all supersaturations, with a tendency for CCN underprediction (15±8%; r2=0.92) at lower supersaturations (0.2-0.4%). Including the effects of the water-soluble organic fraction (which represents around 70% of the total organic content) reduces the underprediction bias at low supersaturations, but introduces a slight overprediction (around 5±15%) bias at higher supersaturations (0.6–0.8%), likely from size-dependent variations of the sulfate to organic ratio. 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 fraction is sufficient for the description of the CCN activity in this area.

Download Full-text

Cloud condensation nuclei activity, closure, and droplet growth kinetics of Houston aerosol during the Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS)

Journal of Geophysical Research Atmospheres ◽

10.1029/2008jd011699 ◽

2009 ◽

Vol 114 ◽

Cited By ~ 76

Author(s):

Sara Lance ◽

Athanasios Nenes ◽

Claudio Mazzoleni ◽

Manvendra K. Dubey ◽

Harmony Gates ◽

...

Keyword(s):

Gulf Of Mexico ◽

Growth Kinetics ◽

Cloud Condensation Nuclei ◽

Atmospheric Composition ◽

Droplet Growth ◽

Condensation Nuclei ◽

Kinetics Of ◽

Climate Study

Download Full-text

Relating CCN activity, volatility, and droplet growth kinetics of β-caryophyllene secondary organic aerosol

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-795-2009 ◽

2009 ◽

Vol 9 (3) ◽

pp. 795-812 ◽

Cited By ~ 141

Author(s):

A. Asa-Awuku ◽

G. J. Engelhart ◽

B. H. Lee ◽

S. N. Pandis ◽

A. Nenes

Keyword(s):

Growth Kinetics ◽

Secondary Organic Aerosol ◽

Active Material ◽

Organic Aerosol ◽

Droplet Formation ◽

Water Soluble ◽

Cloud Condensation Nucleus ◽

Droplet Growth ◽

Kinetics Of ◽

Ccn Activity

Abstract. This study investigates the droplet formation characteristics of secondary organic aerosol (SOA) formed during the ozonolysis of sesquiterpene β-caryophyllene (with and without hydroxyl radicals present). Emphasis is placed on understanding the role of semi-volatile material on Cloud Condensation Nucleus (CCN) activity and droplet growth kinetics. Aging of β-caryophyllene SOA significantly affects all CCN-relevant properties measured throughout the experiments. Using a thermodenuder and two CCN instruments, we find that CCN activity is a strong function of temperature (activation diameter at ~0.6% supersaturation: 100±10 nm at 20°C and 130±10 nm at 35°C), suggesting that the hygroscopic fraction of the SOA is volatile. The water-soluble organic carbon (WSOC) is extracted from the SOA and characterized with Köhler Theory Analysis (KTA); the results suggest that the WSOC is composed of low molecular weight (<200 g mol−1) slightly surface-active material that constitute 5–15% of the SOA mass. These properties are similar to the water-soluble fraction of monoterpene SOA, suggesting that predictive understanding of SOA CCN activity requires knowledge of the WSOC fraction but not its exact speciation. Droplet growth kinetics of the CCN are found to be strongly anticorrelated with WSOC fraction, suggesting that the insoluble material in the SOA forms a kinetic barrier that delays droplet growth. Overall, volatilization effects can increase activation diameters by 30%, and depress droplet growth rate by a factor of two; these results may have important implications for the droplet formation characteristics of SOA, and the atmospheric relevance of CCN measurements carried out at temperatures different from ambient.

Download Full-text

Measurements of cloud condensation nuclei activity and droplet activation kinetics of fresh unprocessed regional dust samples and minerals

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-3527-2011 ◽

2011 ◽

Vol 11 (7) ◽

pp. 3527-3541 ◽

Cited By ~ 88

Author(s):

P. Kumar ◽

I. N. Sokolik ◽

A. Nenes

Keyword(s):

Ammonium Sulfate ◽

Mineral Dust ◽

Cloud Condensation Nuclei ◽

Dust Particles ◽

Droplet Growth ◽

Condensation Nuclei ◽

Activation Kinetics ◽

Droplet Activation ◽

Kinetics Of ◽

Ccn Activity

Abstract. This study reports laboratory measurements of cloud condensation nuclei (CCN) activity and droplet activation kinetics of aerosols dry generated from clays, calcite, quartz, and desert soil samples from Northern Africa, East Asia/China, and Northern America. Based on the observed dependence of critical supersaturation, sc, with particle dry diameter, Ddry, we found that FHH (Frenkel, Halsey and Hill) adsorption activation theory is a far more suitable framework for describing fresh dust CCN activity than Köhler theory. One set of FHH parameters (AFHH ∼ 2.25 ± 0.75, BFHH ∼ 1.20 ± 0.10) can adequately reproduce the measured CCN activity for all species considered, and also explains the large range of hygroscopicities reported in the literature. Based on a threshold droplet growth analysis, mineral dust aerosols were found to display retarded activation kinetics compared to ammonium sulfate. Comprehensive simulations of mineral dust activation and growth in the CCN instrument suggest that this retardation is equivalent to a reduction of the water vapor uptake coefficient (relative to that for calibration ammonium sulfate aerosol) by 30–80%. These results suggest that dust particles do not require deliquescent material to act as CCN in the atmosphere.

Download Full-text

Measurements of cloud condensation nuclei activity and droplet activation kinetics of fresh unprocessed regional dust samples and minerals

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-31039-2010 ◽

2010 ◽

Vol 10 (12) ◽

pp. 31039-31081 ◽

Cited By ~ 5

Author(s):

P. Kumar ◽

I. N. Sokolik ◽

A. Nenes

Keyword(s):

Ammonium Sulfate ◽

Mineral Dust ◽

Cloud Condensation Nuclei ◽

Dust Particles ◽

Droplet Growth ◽

Condensation Nuclei ◽

Activation Kinetics ◽

Droplet Activation ◽

Kinetics Of ◽

Ccn Activity

Abstract. This study reports laboratory measurements of cloud condensation nuclei (CCN) activity and droplet activation kinetics of aerosols dry-generated from clays, calcite, quartz, and desert soil samples from Northern Africa, East Asia/China, and Northern America. Based on the observed dependence of critical supersaturation, sc, with particle dry diameter, Ddry, we find that FHH adsorption activation theory is a far more suitable framework for describing fresh dust CCN activity than Köhler theory. One set of FHH parameters (AFFH ~ 2.25 ± 0.75, BFFH ~ 1.20 ± 0.10) can adequately reproduce the measured CCN activity for all species considered, and also explains the large range of hygroscopicities reported in the literature. Based on threshold droplet growth analysis, mineral dust aerosols were found to display retarded activation kinetics compared to ammonium sulfate. Comprehensive simulations of mineral dust activation and growth in the CCN instrument suggest that this retardation is equivalent to a reduction of the water vapor uptake coefficient (relative to that for calibration ammonium sulfate aerosol) by 30–80%. These results suggest that dust particles do not require deliquescent material to act as CCN in the atmosphere.

Download Full-text

Cloud condensation nuclei activity and droplet activation kinetics of wet processed regional dust samples and minerals

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-8661-2011 ◽

2011 ◽

Vol 11 (16) ◽

pp. 8661-8676 ◽

Cited By ~ 49

Author(s):

P. Kumar ◽

I. N. Sokolik ◽

A. Nenes

Keyword(s):

Cloud Condensation Nuclei ◽

Aqueous Suspension ◽

Droplet Growth ◽

Generation Process ◽

Size Distributions ◽

Condensation Nuclei ◽

Activation Kinetics ◽

Droplet Activation ◽

Kinetics Of ◽

Ccn Activity

Abstract. This study reports laboratory measurements of particle size distributions, cloud condensation nuclei (CCN) activity, and droplet activation kinetics of wet generated aerosols from clays, calcite, quartz, and desert soil samples from Northern Africa, East Asia/China, and Northern America. The dependence of critical supersaturation, sc, on particle dry diameter, Ddry, is used to characterize particle-water interactions and assess the ability of Frenkel-Halsey-Hill adsorption activation theory (FHH-AT) and Köhler theory (KT) to describe the CCN activity of the considered samples. Wet generated regional dust samples produce unimodal size distributions with particle sizes as small as 40 nm, CCN activation consistent with KT, and exhibit hygroscopicity similar to inorganic salts. Wet generated clays and minerals produce a bimodal size distribution; the CCN activity of the smaller mode is consistent with KT, while the larger mode is less hydrophilic, follows activation by FHH-AT, and displays almost identical CCN activity to dry generated dust. Ion Chromatography (IC) analysis performed on regional dust samples indicates a soluble fraction that cannot explain the CCN activity of dry or wet generated dust. A mass balance and hygroscopicity closure suggests that the small amount of ions (from low solubility compounds like calcite) present in the dry dust dissolve in the aqueous suspension during the wet generation process and give rise to the observed small hygroscopic mode. Overall these results identify an artifact that may question the atmospheric relevance of dust CCN activity studies using the wet generation method. Based on the method of threshold droplet growth analysis, wet generated mineral aerosols display similar activation kinetics compared to ammonium sulfate calibration aerosol. Finally, a unified CCN activity framework that accounts for concurrent effects of solute and adsorption is developed to describe the CCN activity of aged or hygroscopic dusts.

Download Full-text

CCN activity and droplet growth kinetics of fresh and aged monoterpene secondary organic aerosol

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-8-95-2008 ◽

2008 ◽

Vol 8 (1) ◽

pp. 95-135 ◽

Cited By ~ 5

Author(s):

G. J. Engelhart ◽

A. Asa-Awuku ◽

A. Nenes ◽

S. N. Pandis

Keyword(s):

Surface Tension ◽

Growth Kinetics ◽

Molar Mass ◽

Secondary Organic Aerosol ◽

Organic Aerosol ◽

Water Soluble ◽

Droplet Growth ◽

Kohler Theory ◽

Kinetics Of ◽

Ccn Activity

Abstract. The ability of secondary organic aerosol (SOA) produced from the ozonolysis of α-pinene and monoterpene mixtures (α-pinene, β-pinene, limonene and 3-carene) to become cloud droplets was investigated. Monoterpene SOA is quite active and would likely be a good source of cloud condensation nuclei (CCN) in the atmosphere. A static CCN counter and a Scanning Mobility CCN Analyser (a Scanning Mobility Particle Sizer coupled with a Continuous Flow counter) were used for the CCN measurements. A decrease in CCN activation diameter for α-pinene SOA of approximately 3 nm h−1 was observed as the aerosol continued to react with oxidants. Hydroxyl radicals further oxidize the SOA particles thereby enhancing the particle CCN activity with time. The initial concentrations of ozone and monoterpene precursor (for concentrations lower than 40 ppb) do not appear to affect the activity of the resulting SOA. Köhler Theory Analysis (KTA) is used to infer the molar mass of the SOA sampled online and offline from atomized filter samples. KTA suggests that the aged aerosol (both from α-pinene and the mixed monoterpene oxidation) is primarily water-soluble (around 70–80%), with an estimated average molar mass of 180±55 g mol−1 (consistent with existing SOA speciation studies). CCN activity measurements of the SOA mixed with (NH4)2SO4 suggest that the organic can depress surface tension by as much as 10 nM m−1 (with respect to pure water). The droplet growth kinetics of SOA samples are similar to (NH4)2SO4, except at low supersaturation, where SOA tends to grow more slowly. The CCN activity of α-pinene and mixed monoterpene SOA can be modelled by a very simple implementation of Köhler theory, assuming complete dissolution of the particles, no dissociation into ions, molecular weight of 180 g mol−1, density of 1.5 g cm−3, and surface tension to within 10–15% of water.

Download Full-text

Relating CCN activity, volatility, and droplet growth kinetics of β-caryophyllene secondary organic aerosol

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-8-10105-2008 ◽

2008 ◽

Vol 8 (3) ◽

pp. 10105-10151 ◽

Cited By ~ 5

Author(s):

A. Asa-Awuku ◽

G. J. Engelhart ◽

B. H. Lee ◽

S. N. Pandis ◽

A. Nenes

Keyword(s):

Growth Kinetics ◽

Secondary Organic Aerosol ◽

Active Material ◽

Organic Aerosol ◽

Droplet Formation ◽

Water Soluble ◽

Cloud Condensation Nucleus ◽

Droplet Growth ◽

Kinetics Of ◽

Ccn Activity

Abstract. This study investigates the droplet formation characteristics of secondary organic aerosol (SOA) formed during the ozonolysis of sesquiterpene β-caryophyllene (with and without hydroxyl radicals present). Emphasis is placed on understanding the role of semi-volatile material on Cloud Condensation Nucleus (CCN) activity and droplet growth kinetics. Aging of β-caryophyllene SOA significantly affects all CCN-relevant properties measured throughout the experiments. Using a thermodenuder and two CCN instruments, we find that CCN activity is a strong function of temperature (activation diameter at ~0.6% supersaturation: 100±10 nm at 20°C and 130±10 nm at 35°C), suggesting that the hygroscopic fraction of the SOA is volatile. The water-soluble organic carbon (WSOC) is extracted from the SOA and characterized with Köhler Theory Analysis (KTA); the results suggest that the WSOC is composed of low molecular weight (<200 g mol−1) slightly surface-active material that constitute 5–15% of the SOA mass. These properties are similar to the water-soluble fraction of monoterpene SOA, suggesting that predictive understanding of SOA CCN activity requires knowledge of the WSOC fraction but not its exact speciation. Droplet growth kinetics of the CCN are found to be strongly anticorrelated with WSOC fraction, suggesting that the insoluble material in the SOA forms a kinetic barrier that delays droplet growth. These results have important implications for the droplet formation characteristics of SOA, and the atmospheric relevance of CCN measurements carried out at temperatures different from ambient.

Download Full-text