scholarly journals Molar mass, surface tension, and droplet growth kinetics of marine organics from measurements of CCN activity

2008 ◽  
Vol 35 (7) ◽  
pp. n/a-n/a ◽  
Author(s):  
R. H. Moore ◽  
E. D. Ingall ◽  
A. Sorooshian ◽  
A. Nenes
Keyword(s):  
Surface Tension ◽  
Growth Kinetics ◽  
Molar Mass ◽  
Droplet Growth ◽  
Kinetics Of ◽  
Ccn Activity

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

2008 ◽  
Vol 8 (1) ◽  
pp. 95-135 ◽  
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.

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

2008 ◽  
Vol 8 (14) ◽  
pp. 3937-3949 ◽  
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.

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

2009 ◽  
Vol 9 (3) ◽  
pp. 795-812 ◽  
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.

scholarly journals Alkene ozonolysis SOA: inferences of composition and droplet growth kinetics from Köhler theory analysis

2007 ◽  
Vol 7 (3) ◽  
pp. 8983-9011 ◽  
Author(s):  
A. Asa-Awuku ◽  
A. Nenes ◽  
S. Gao ◽  
R. C. Flagan ◽  
J. H. Seinfeld
Keyword(s):  
Surface Tension ◽  
Growth Kinetics ◽  
Organic Aerosol ◽  
Water Soluble ◽  
Total Carbon ◽  
Droplet Growth ◽  
Theory Analysis ◽  
Kohler Theory ◽  
Surface Active ◽  
Ccn Activity

Abstract. The CCN properties, surfactant characteristics, and droplet growth kinetics of secondary organic aerosol (SOA) formed from the ozonolysis of three parent alkene hydrocarbons (terpinolene, 1-methlycycloheptene and cycloheptene) are explored. Based on measurements of CCN activity, total carbon and inorganic ion concentrations, we estimate the average molar volume of the water-soluble organic component using Köhler Theory Analysis (KTA). The results suggest that the water-soluble organics in the SOA are composed of relatively low molecular weight species, with an effective molar mass less than 200 g mol−1. This finding is consistent with the speciated fraction for some of the SOA, and suggests that KTA can be applied to complex organic aerosol, such as that found in the atmosphere. From measurements of CCN activity and Köhler Theory, we apply a novel method to infer the surface tension at the point of activation; this is used to infer the presence of surface-active organics. It is found that the water-soluble carbon can be surface-active, depressing surface tension 10–15% from that of pure water at concentrations relevant for CCN activation. Although important, this level of surface tension depression is lower than expected for HULIS, which suggest that they are not likely in the SOA examined. In all cases, the CCN exhibit droplet growth kinetics similar to (NH4)2SO4.

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

2008 ◽  
Vol 8 (3) ◽  
pp. 10105-10151 ◽  
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.

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

2016 ◽  
Vol 16 (2) ◽  
pp. 1105-1121 ◽  
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.

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

2015 ◽  
Vol 15 (14) ◽  
pp. 19903-19945 ◽  
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.

scholarly journals Mixing state and compositional effects on CCN activity and droplet growth kinetics of size-resolved CCN in an urban environment

2012 ◽  
Vol 12 (21) ◽  
pp. 10239-10255 ◽  
Author(s):  
L. T. Padró ◽  
R. H. Moore ◽  
X. Zhang ◽  
N. Rastogi ◽  
R. J. Weber ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Water Soluble ◽  
Anthropogenic Sources ◽  
Droplet Growth ◽  
Mixing State ◽  
Aerosol Composition ◽  
Activation Kinetics ◽  
Aerosol Mixing State ◽  
Kinetics Of ◽  
Ccn Activity

Abstract. Aerosol composition and mixing state near anthropogenic sources can be highly variable and can challenge predictions of cloud condensation nuclei (CCN). The impacts of chemical composition on CCN activation kinetics is also an important, but largely unknown, aspect of cloud droplet formation. Towards this, we present in-situ size-resolved CCN measurements carried out during the 2008 summertime August Mini Intensive Gas and Aerosol Study (AMIGAS) campaign in Atlanta, GA. Aerosol chemical composition was measured by two particle-into-liquid samplers measuring water-soluble inorganic ions and total water-soluble organic carbon. Size-resolved CCN data were collected using the Scanning Mobility CCN Analysis (SMCA) method and were used to obtain characteristic aerosol hygroscopicity distributions, whose breadth reflects the aerosol compositional variability and mixing state. Knowledge of aerosol mixing state is important for accurate predictions of CCN concentrations and that the influence of an externally-mixed, CCN-active aerosol fraction varies with size from 31% for particle diameters less than 40 nm to 93% for accumulation mode aerosol during the day. Assuming size-dependent aerosol mixing state and size-invariant chemical composition decreases the average CCN concentration overprediction (for all but one mixing state and chemical composition scenario considered) from over 190–240% to less than 20%. CCN activity is parameterized using a single hygroscopicity parameter, κ, which averages to 0.16 ± 0.07 for 80 nm particles and exhibits considerable variability (from 0.03 to 0.48) throughout the study period. Particles in the 60–100 nm range exhibited similar hygroscopicity, with a κ range for 60 nm between 0.06–0.076 (mean of 0.18 ± 0.09). Smaller particles (40 nm) had on average greater κ, with a range of 0.20–0.92 (mean of 0.3 ± 0.12). Analysis of the droplet activation kinetics of the aerosol sampled suggests that most of the CCN activate as rapidly as calibration aerosol, suggesting that aerosol composition exhibits a minor (if any) impact on CCN activation kinetics.

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

2012 ◽  
Vol 47 ◽  
pp. 389-398 ◽  
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
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