Characterization of Sesquiterpene Secondary Organic Aerosol: Thermodynamic Properties, Aging Characteristics, CCN Activity, and Droplet Growth Kinetic Analysis

Cloud condensation nuclei (CCN) activity and the hygroscopicity of secondary organic aerosol (SOA) depends on the particle size and composition, explicitly, the thermodynamic properties of the aerosol solute and subsequent interactions with water. The gas-to-aerosol phase partitioning is critical for aerosol composition and thus gas-phase vapors and kinetics can play an important role in the CCN activity of SOA.

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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.

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CCN activity and volatility of β-caryophyllene secondary organic aerosol

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-20745-2012 ◽

2012 ◽

Vol 12 (8) ◽

pp. 20745-20783

Author(s):

M. Frosch ◽

M. Bilde ◽

A. Nenes ◽

A. P. Praplan ◽

Z. Jurányi ◽

...

Keyword(s):

Secondary Organic Aerosol ◽

Light Exposure ◽

Cloud Condensation Nuclei ◽

Organic Aerosol ◽

Droplet Growth ◽

Experimental Conditions ◽

Initial Injection ◽

Different Temperatures ◽

Kinetics Of ◽

Ccn Activity

Abstract. In a series of smog chamber experiments, the Cloud Condensation Nuclei (CCN) activity of Secondary Organic Aerosol (SOA) generated from ozonolysis of β-caryophyllene was characterized by determining the CCN derived hygroscopicity parameter, κCCN, from experimental data. Two types of CCN counters, operating at different temperatures, were used. The effect of semi-volatile organic compounds on the CCN activity of SOA was studied using a thermodenuder. Overall, SOA was only slightly CCN active (with κCCN in the range 0.001–0.16), and in dark experiments with no OH scavenger present, κCCN decreased when particles were sent through the thermodenuder (with a temperature up to 50 °C). SOA was generated under different experimental conditions: in some experiments, an OH scavenger (2-butanol) was added. SOA from these experiments was less CCN active than SOA produced in experiments without an OH scavenger (i.e. where OH was produced during ozonolysis). In other experiments, lights were turned on, either without or with the addition of HONO (OH source). This led to the formation of more CCN active SOA. SOA was aged up to 30 h through exposure to ozone and (in experiments with no OH scavenger present) to OH. In all experiments, the derived κCCN consistently increased with time after initial injection of β-caryophyllene, showing that chemical ageing increases the CCN activity of β-caryophyllene SOA. κCCN was also observed to depend on supersaturation, which was explained either as an evaporation artifact from semi-volatile SOA (only observed in experiments lacking light exposure) or, alternatively, by effects related to chemical composition depending on dry particle size. Using the method of Threshold Droplet Growth Analysis it was also concluded that the activation kinetics of the SOA do not differ significantly from calibration ammonium sulphate aerosol.

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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.

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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.

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

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-3937-2008 ◽

2008 ◽

Vol 8 (14) ◽

pp. 3937-3949 ◽

Cited By ~ 166

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. 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. Consistent with previous studies monoterpene SOA is quite active and would likely be a good source of cloud condensation nuclei (CCN) in the atmosphere. A decrease in CCN activation diameter for α-pinene SOA of approximately 3 nm hr−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. The estimated average molar mass of online SOA was determined to be 180±55 g mol−1 (consistent with existing SOA speciation studies) assuming complete solubility. KTA suggests that the aged aerosol (both from α-pinene and the mixed monoterpene oxidation) is primarily water-soluble (around 65%). CCN activity measurements of the SOA mixed with (NH4)2SO4 suggest that the organic can depress surface tension by as much as 10 N 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 activation diameter of α-pinene and mixed monoterpene SOA can be modelled to within 10–15% of experiments by a simple implementation of Köhler theory, assuming complete dissolution of the particles, no dissociation into ions, a molecular weight of 180 g mol−1, a density of 1.5 g cm−3, and the surface tension of water.

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CCN activity and volatility of β-caryophyllene secondary organic aerosol

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-2283-2013 ◽

2013 ◽

Vol 13 (4) ◽

pp. 2283-2297 ◽

Cited By ~ 18

Author(s):

M. Frosch ◽

M. Bilde ◽

A. Nenes ◽

A. P. Praplan ◽

Z. Jurányi ◽

...

Keyword(s):

Secondary Organic Aerosol ◽

Light Exposure ◽

Cloud Condensation Nuclei ◽

Organic Aerosol ◽

Droplet Growth ◽

Experimental Conditions ◽

Initial Injection ◽

Different Temperatures ◽

Kinetics Of ◽

Ccn Activity

Abstract. In a series of smog chamber experiments, the cloud condensation nuclei (CCN) activity of secondary organic aerosol (SOA) generated from ozonolysis of β-caryophyllene was characterized by determining the CCN derived hygroscopicity parameter, κCCN, from experimental data. Two types of CCN counters, operating at different temperatures, were used. The effect of semi-volatile organic compounds on the CCN activity of SOA was studied using a thermodenuder. Overall, SOA was only slightly CCN active (with κCCN in the range 0.001–0.16), and in dark experiments with no OH scavenger present, κCCN decreased when particles were sent through the thermodenuder (with a temperature up to 50 °C). SOA was generated under different experimental conditions: In some experiments, an OH scavenger (2-butanol) was added. SOA from these experiments was less CCN active than SOA produced in experiments without an OH scavenger (i.e. where OH was produced during ozonolysis). In other experiments, lights were turned on, either without or with the addition of HONO (OH source). This led to the formation of more CCN active SOA. SOA was aged up to 30 h through exposure to ozone and (in experiments with no OH scavenger present) to OH. In all experiments, the derived κCCN consistently increased with time after initial injection of β-caryophyllene, showing that chemical ageing increases the CCN activity of β-caryophyllene SOA. κCCN was also observed to depend on supersaturation, which was explained either as an evaporation artifact from semi-volatile SOA (only observed in experiments lacking light exposure) or, alternatively, by effects related to chemical composition depending on dry particle size. Using the method of Threshold Droplet Growth Analysis it was also concluded that the activation kinetics of the SOA do not differ significantly from calibration ammonium sulphate aerosol for particles aged for several hours.

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Cloud condensation nuclei activity, droplet growth kinetics, and hygroscopicity of biogenic and anthropogenic secondary organic aerosol (SOA)

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-1105-2016 ◽

2016 ◽

Vol 16 (2) ◽

pp. 1105-1121 ◽

Cited By ~ 19

Author(s):

D. F. Zhao ◽

A. Buchholz ◽

B. Kortner ◽

P. Schlag ◽

F. Rubach ◽

...

Keyword(s):

Growth Kinetics ◽

Secondary Organic Aerosol ◽

Cloud Condensation Nuclei ◽

Cloud Droplet ◽

Organic Aerosol ◽

Droplet Growth ◽

Biogenic Voc ◽

Degree Of Oxidation ◽

Kinetics Of ◽

Ccn Activity

Abstract. Interaction of biogenic volatile organic compounds (VOCs) with Anthropogenic VOC (AVOC) affects the physicochemical properties of secondary organic aerosol (SOA). We investigated cloud droplet activation (CCN activity), droplet growth kinetics, and hygroscopicity of mixed anthropogenic and biogenic SOA (ABSOA) compared to pure biogenic SOA (BSOA) and pure anthropogenic SOA (ASOA). Selected monoterpenes and aromatics were used as representative precursors of BSOA and ASOA, respectively.We found that BSOA, ASOA, and ABSOA had similar CCN activity despite the higher oxygen to carbon ratio (O/C) of ASOA compared to BSOA and ABSOA. For individual reaction systems, CCN activity increased with the degree of oxidation. Yet, when considering all different types of SOA together, the hygroscopicity parameter, κCCN, did not correlate with O/C. Droplet growth kinetics of BSOA, ASOA, and ABSOA were comparable to that of (NH4)2SO4, which indicates that there was no delay in the water uptake for these SOA in supersaturated conditions.In contrast to CCN activity, the hygroscopicity parameter from a hygroscopic tandem differential mobility analyzer (HTDMA) measurement, κHTDMA, of ASOA was distinctively higher (0.09–0.10) than that of BSOA (0.03–0.06), which was attributed to the higher degree of oxidation of ASOA. The ASOA components in mixed ABSOA enhanced aerosol hygroscopicity. Changing the ASOA fraction by adding biogenic VOC (BVOC) to ASOA or vice versa (AVOC to BSOA) changed the hygroscopicity of aerosol, in line with the change in the degree of oxidation of aerosol. However, the hygroscopicity of ABSOA cannot be described by a simple linear combination of pure BSOA and ASOA systems. This indicates that additional processes, possibly oligomerization, affected the hygroscopicity.Closure analysis of CCN and HTDMA data showed κHTDMA was lower than κCCN by 30–70 %. Better closure was achieved for ASOA compared to BSOA. This discrepancy can be attributed to several reasons. ASOA seemed to have higher solubility in subsaturated conditions and/or higher surface tension at the activation point than that of BSOA.

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Cloud condensation nuclei activity, droplet growth kinetics and hygroscopicity of biogenic and anthropogenic Secondary Organic Aerosol (SOA)

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-19903-2015 ◽

2015 ◽

Vol 15 (14) ◽

pp. 19903-19945 ◽

Cited By ~ 5

Author(s):

D. F. Zhao ◽

A. Buchholz ◽

B. Kortner ◽

P. Schlag ◽

F. Rubach ◽

...

Keyword(s):

Growth Kinetics ◽

Secondary Organic Aerosol ◽

Cloud Condensation Nuclei ◽

Cloud Droplet ◽

Organic Aerosol ◽

Droplet Growth ◽

Degree Of Oxidation ◽

Kinetics Of ◽

Aerosol Hygroscopicity ◽

Ccn Activity

Abstract. Interaction of biogenic volatile organic compounds (VOC) with anthropogenic VOC affects the physicochemical properties of secondary organic aerosol (SOA). We investigated cloud droplet activation (CCN activity), droplet growth kinetics, and hygroscopicity of mixed anthropogenic and biogenic SOA (ABSOA) compared to pure biogenic SOA (BSOA) and pure anthropogenic SOA (ASOA). Selected monoterpenes and aromatics were used as representative precursors of BSOA and ASOA, respectively. We found that BSOA, ASOA, and ABSOA had similar CCN activity despite the higher oxygen to carbon ratio (O/C) of ASOA compared to BSOA and ABSOA. For individual reaction systems, CCN activity increased with the degree of oxidation. Yet, when considering all different types of SOA together, the hygroscopicity parameter, κCCN, did not correlate with O/C. Droplet growth kinetics of BSOA, ASOA, and ABSOA was comparable to that of (NH4)2SO4, which indicates that there was no delay in the water uptake for these SOA in supersaturated conditions. In contrast to CCN activity, the hygroscopicity parameter from hygroscopic tandem differential mobility analyzer (HTDMA) measurement, κHTDMA, of ASOA was distinctively higher (0.09–0.10) than that of BSOA (0.03–0.06), which was attributed to the higher degree of oxidation of ASOA. The ASOA components in mixed ABSOA enhanced aerosol hygroscopicity. Changing the ASOA fraction by adding BVOC to ASOA or vice versa AVOC to BSOA changed the hygroscopicity of aerosol, in line with the change in the degree of oxidation of aerosol. However, the hygroscopicity of ABSOA cannot be described by a simple linear combination of pure BSOA and ASOA systems. This indicates that additional processes, possibly oligomerization, affected the hygroscopicity. Closure analysis of CCN and HTDMA data showed κHTDMA was lower than κCCN by 30–70 %. Better closure was achieved for ASOA compared to BSOA. This discrepancy can be attributed to several reasons. ASOA seemed to have higher solubility in subsaturated conditions and/or higher surface tension at the activation point than that of BSOA.

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