scholarly journals Hygroscopic properties of different aerosol types over the Atlantic and Indian Oceans

2003 ◽  
Vol 3 (5) ◽  
pp. 1377-1397 ◽  
Author(s):  
A. Maßling ◽  
A. Wiedensohler ◽  
B. Busch ◽  
C. Neusüß ◽  
P. Quinn ◽  
...  
Keyword(s):  
Light Absorption ◽  
Mass Concentration ◽  
Elemental Carbon ◽  
Size Range ◽  
Field Studies ◽  
Cascade Impactor ◽  
Hygroscopic Growth ◽  
Air Masses ◽  
Hygroscopic Properties ◽  
Time Periods

Abstract. Hygroscopic properties of atmospheric particles were studied in the marine tropospheric boundary layer over the Atlantic and Indian Oceans during two consecutive field studies: the Aerosols99 cruise (Atlantic Ocean) from 15 January to 20 February 1999, and the INDOEX cruise (Indian Ocean Experiment) from 23 February to 30 March 1999. The hygroscopic properties were compared to optical and chemical properties, such as absorption, chemical inorganic composition, and mass concentration of organic and elemental carbon, to identify the influence of these parameters on hygroscopicity. During the two field studies, four types of aerosol-sampling instruments were used on board the NOAA (National Oceanic and Atmospheric Administration) Research Vessel Ronald H. Brown: Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA), seven-stage cascade impactor, two-stage cascade impactor, and Particle Soot Absorption Photometer (PSAP). The HTDMA was used to determine the hygroscopic properties of atmospheric particles at initial dry sizes (Dp) of 50, 150, and 250 nm and at relative humidities (RH) of 30, 55, 75, and 90%. Simultaneously, a seven-stage cascade impactor of which 3 stages were in the sub-mm size range was used to determine the molar composition of the major inorganic ions such as ammonium and sulfate ions. A two-stage cascade impactor (1 in the sub-mm size range, 1 in the sup-mm size range) was used to determine the mass concentration of organic and elemental carbon. The PSAP was used (at a wavelength of 565 nm) to measure the light absorption coefficient of the aerosol. During the two field studies, air masses of several different origins passed the ship's cruise path. The occurrence of different air masses was classified into special time periods signifying the origin of the observed aerosol. All time periods showed a group of particles with high hygroscopic growth. The measured average hygroscopic growth factors defined by the ratio of dry and wet particle diameter at 90% RH ranged from 1.6 to 2.0, depending on the dry particle size and on the type of air mass. Particles with low hygroscopic growth occurred only when continentally influenced air masses arrived at the ship's position. Distinctions in hygroscopic growth of particles of different air masses were more significant for small relative humidities (30% or 55% RH). High concentrations of elemental carbon corresponded with high light absorption coefficients and with the occurrence of less-hygroscopic and nearly hydrophobic particle fractions in the hygroscopic growth distributions. A key finding is that clean marine air masses that had no land contact for five to six days could clearly be distinguished from polluted air masses that had passed over a continent several days before reaching the ship.

scholarly journals Hygroscopic properties of different aerosol types over the Atlantic and Indian Oceans

2003 ◽  
Vol 3 (1) ◽  
pp. 135-185 ◽  
Author(s):  
A. Maßling ◽  
A. Wiedensohler ◽  
B. Busch ◽  
C. Neusüß ◽  
P. Quinn ◽  
...  
Keyword(s):  
Mass Concentration ◽  
Elemental Carbon ◽  
Size Range ◽  
Field Studies ◽  
Cascade Impactor ◽  
Hygroscopic Growth ◽  
Air Masses ◽  
Hygroscopic Properties ◽  
Time Periods ◽  
Marine Air

Abstract. Hygroscopic properties of atmospheric particles were studied in the marine tropospheric boundary layer over the Atlantic and Indian Oceans during two consecutive field studies: the Aerosols99 cruise (Atlantic Ocean) from 15 January to 20 February 1999, and the INDOEX cruise (Indian Ocean Experiment) from 23 February to 30 March 1999. The hygroscopic properties were compared to optical and chemical properties, such as absorption, chemical inorganic composition, and mass concentration of organic and elemental carbon, to identify the influence of these parameters on hygroscopicity. During the two field studies, four types of aerosol-sampling instruments were used on board the NOAA (Northern Organization Atlantic Administration) Research Vessel Ronald H Brown: Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA), seven-stage cascade impactor, two-stage cascade impactor, and Particle Soot Absorption Photometer (PSAP). The HTDMA was used to determine the hygroscopic properties of atmospheric particles at initial dry sizes (Dp) of 50, 150, and 250 nm and at relative humidities (RH) of 30, 55, 75, and 90%. The HTDMA data provide insight into the mixing state of the aerosol in terms of its hygroscopic behavior. Simultaneously, a seven-stage cascade impactor (3 in the sub-µm size range) was used to determine the molar composition of the major inorganic ions such as ammonium and sulfate ions. A two-stage cascade impactor (1 in the sub-µm size range, 1 in the sup-µm size range) was used to determine the mass concentration of organic and elemental carbon. The PSAP was used (at a wavelength of 565 nm) to measure the light absorption coefficient of the aerosol. During the two field studies, air masses of several different origins passed the ship's cruise path. The air mass back-trajectory analysis revealed marine air masses as well as air masses with continental influence from Africa, India, or Arabia. The occurrence of different air masses was classified into special time periods signifying the origin of the observed aerosol. All time periods showed a group of particles with high hygroscopic growth. The measured average hygroscopic growth factors ranged from 1.6 to 2.0, depending on the dry particle size and on the type of air mass. Particles with low hygroscopic growth occurred only when continentally influenced air masses arrived at the ship's position. Distinctions in hygroscopic growth of particles of different air masses were more significant for small relative humidities (30% or 55% RH). High concentrations of elemental carbon corresponded with high light absorption coefficients and with the occurrence of less-hygroscopic and nearly hydrophobic particle fractions in the hygroscopic growth distributions. Finally, a solubility model was used to calculate soluble particle volume fractions for air masses of different origin in the Northern and Southern Hemispheres. A key finding is that clean marine air masses that had no land contact for five to six days could clearly be distinguished from polluted air masses that had passed over a continent several days before reaching the ship. This distinction was based on results by taking into account only the hygroscopic characteristics and the solubility of the observed particles.

scholarly journals Particle hygroscopicity and its link to chemical composition in the urban atmosphere of Beijing, China during summertime

2015 ◽  
Vol 15 (8) ◽  
pp. 11495-11524 ◽  
Author(s):  
Z. J. Wu ◽  
J. Zheng ◽  
D. J. Shang ◽  
Z. F. Du ◽  
Y. S. Wu ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Mass Concentration ◽  
Cloud Condensation Nuclei ◽  
Empirical Relationship ◽  
Urban Atmosphere ◽  
High Time Resolution ◽  
Hygroscopic Growth ◽  
Hygroscopic Properties ◽  
Beijing China ◽  
Measurement Period

Abstract. Simultaneous measurements of particle number size distribution, particle hygroscopic properties, and size-resolved chemical composition were made during the summer of 2014 in Beijing, China. During the measurement period, the median hygroscopicity parameters (κ) of 50, 100, 150, 200, and 250 nm particles are respectively 0.15, 0.19, 0.22, 0.27, and 0.29, showing an increasing trend with increasing particle size. When PM2.5 mass concentration is greater than 50 μg m−3, the fractions of the hydrophilic mode for 150, 250, 350 nm particles increased towards 1 as PM2.5 mass concentration increased. This indicates that aged particles dominated during severe pollution periods in the atmosphere of Beijing. Particle hygroscopic growth can be well predicted using high time-resolution size-resolved chemical composition derived from AMS measurement on a basis of ZSR mixing rule. An empirical relationship between κ of organic fraction (κorg) and oxygen to carbon ratio (O : C) (κorg= 0.08·O : C+0.02) is obtained. During new particle formation event associating with strongly active photochemistry, the hygroscopic growth factor or κ of newly formed particles is greater than for particle with the same sizes during non-NPF periods. A quick transformation from external mixture to internal mixture for pre-existing particles (for example 250 nm particle) was observed. Such transformations can modify the state of mixture of pre-exiting particles and thus modify properties such as the light absorption coefficient and cloud condensation nuclei activation.

scholarly journals Quantifying black carbon light absorption enhancement by a novel statistical approach

2017 ◽  
Author(s):  
Cheng Wu ◽  
Dui Wu ◽  
Jian Zhen Yu
Keyword(s):  
Black Carbon ◽  
Light Absorption ◽  
Seasonal Pattern ◽  
Absorption Efficiency ◽  
Absorption Enhancement ◽  
Hygroscopic Growth ◽  
Pearl River Delta Region ◽  
Coating Materials ◽  
Air Masses ◽  
The Pearl River

Abstract. Black carbon (BC) particles in the atmosphere can absorb more light when coated by non-absorbing or weakly absorbing materials during atmospheric aging, due to the lensing effect. In this study, the light absorption enhancement factor, Eabs, was quantified using one year's measurement of mass absorption efficiency (MAE) in the Pearl River Delta region (PRD). A new approach for calculating primary MAE (MAEp), the key for Eabs estimation, is demonstrated using the Minimum R Squared (MRS) method, exploring the inherent source independency between BC and its coating materials. The annual average Eabs is found to be 1.52, exhibiting a clear seasonal pattern with higher values in summer and lower in the winter. Elevated Eabs in the rainy summer season is likely associated with aged air masses dominating from marine origin, along with long-range transport of biomass burning influenced air masses from Southeast Asia. Eabs induced by hygroscopic growth at elevated RH could be as high as 1.3. Core-shell Mie simulations along with measured Eabs and Angstrom absorption exponent (AAE) constraints suggest that in the PRD, the coating materials are unlikely to be dominated by brown carbon and the coating thickness is higher in the rainy season than the dry season. A negative correlation is found between AAE470–660 and RH, suggesting a dominant particle size of Dcore = 130 nm and Dshell/Dcore range of 2 to 4.

scholarly journals Hygroscopic properties of newly formed ultrafine particles at an urban site surrounded by a deciduous forest in northern Japan during the summer of 2011

2014 ◽  
Vol 14 (6) ◽  
pp. 8257-8285
Author(s):  
J. Jung ◽  
K. Kawamura
Keyword(s):  
Growth Factors ◽  
Ultrafine Particles ◽  
Deciduous Forest ◽  
Urban Site ◽  
Hygroscopic Growth ◽  
Air Masses ◽  
Hygroscopic Property ◽  
Nucleation Mode ◽  
Hygroscopic Properties ◽  
Northern Japan

Abstract. To investigate the hygroscopic property of ultrafine particles during the new particle formation event, hygroscopic growth factors (g(RH)) of size-segregated atmospheric particles were measured at an urban site in Sapporo, northern Japan, during the summer of 2011. Hygroscopic growth factors at 85% RH (g(85%)) of freshly formed nucleation mode particles were measured at a dry particle diameter (Dp) centered at 20 nm to be 1.11 to 1.28 (average 1.16 ± 0.06), which are equivalent to 1.17 to 1.35 (1.23 ± 0.06) for a dry Dp centered at 100 nm after considering the Kelvin effect. These values are comparable with those of secondary organic aerosols, suggesting that low-volatility organic vapors are important to the burst of nucleation mode particles at the measurement site surrounded by a deciduous forest. Gradual increases in mode diameter after the burst of nucleation mode particles were obtained under southerly wind condition with a dominant contribution of intermediately-hygroscopic particles. However, sharp increases in mode diameter were obtained when wind direction shifted to northwesterly or northeasterly with a sharp increase in highly-hygroscopic particle faction in the Aitken mode particles, indicating that local wind direction is an important factor controlling the growth of newly formed particles and their hygroscopic properties. Higher g(85%) values (1.27 ± 0.05) were obtained at a dry Dp of 120 nm when the air masses originated from the Asian Continent, whereas lower g(85%) values (1.19 ± 0.06) were obtained when clean marine air masses arrived at the urban site. These results indicate that the hygroscopic property of large Aitken and small accumulation mode particles (80–165 nm) is highly influenced by the long-range atmospheric transport of particles and their precursors.

scholarly journals Hygroscopic properties of atmospheric aerosol particles over the Eastern Mediterranean: implications for regional direct radiative forcing under clean and polluted conditions

2011 ◽  
Vol 11 (9) ◽  
pp. 4251-4271 ◽  
Author(s):  
M. Stock ◽  
Y. F. Cheng ◽  
W. Birmili ◽  
A. Massling ◽  
B. Wehner ◽  
...  
Keyword(s):  
Growth Factors ◽  
Radiative Forcing ◽  
Eastern Mediterranean ◽  
Hygroscopic Growth ◽  
Differential Mobility ◽  
Air Mass ◽  
Air Masses ◽  
Hygroscopic Properties ◽  
Direct Radiative Forcing ◽  
Marine Air

Abstract. This work examines the effect of direct radiative forcing of aerosols in the eastern Mediterranean troposphere as a function of air mass composition, particle size distribution and hygroscopicity, and relative humidity (RH). During intensive field measurements on the island of Crete, Greece, the hygroscopic properties of atmospheric particles were determined using a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) and a Hygroscopicity Differential Mobility Analyzer-Aerodynamic Particle Sizer (H-DMA-APS). Similar to former studies, the H-TDMA identified three hygroscopic sub-fractions of particles in the sub-μm range: a more hygroscopic group, a less hygroscopic group and a nearly hydrophobic particle group. The average hygroscopic particle growth factors at 90 % RH were a significant function of particle mobility diameter (Dp): 1.42 (± 0.05) at 30 nm compared to 1.63 (± 0.07) at 250 nm. The H-DMA-APS identified up to three hygroscopic sub-fractions at mobility diameters of 1.0 and 1.2 μm. The data recorded between 12 August and 20 October 2005 were classified into four distinct synoptic-scale air mass types distinguishing between different regions of origin (western Mediterranean vs. the Aegean Sea) as well as the degree of continental pollution (marine vs. continentally influenced). The hygroscopic properties of particles with diameter Dp≥150 nm showed the most pronounced dependency on air mass origin, with growth factors in marine air masses exceeding those in continentally influenced air masses. Particle size distributions and hygroscopic growth factors were used to calculate aerosol light scattering coefficients at ambient RH using a Mie model. A main result was the pronounced enhancement of particle scattering over the eastern Mediterranean due to hygroscopic growth, both in the marine and continentally influenced air masses. When RH reached its summer daytime values around 70–80 %, up to 50–70 % of the calculated visibility reduction was due to the hygroscopic growth of the particles by water compared to the effect of the dry particles alone. The estimated aerosol direct radiative forcings for both, marine and continentally influenced air masses were negative indicating a net cooling of the atmosphere due to the aerosol. The radiative forcing ΔFr was nevertheless governed by the total aerosol concentration most of the time: ΔFr was typically more negative for continentally influenced aerosols (ca. −4 W m−2) compared to rather clean marine aerosols (ca. −1.5 W m−2). When RH occasionally reached 90 % in marine air masses, ΔFr even reached values down to −7 W m−2. Our results emphasize, on the basis of explicit particle hygroscopicity measurements, the relevance of ambient RH for the radiative forcing of regional atmospheres.

scholarly journals Hygroscopic properties of atmospheric aerosol particles over the Eastern Mediterranean: implications for regional direct radiative forcing under clean and polluted conditions

2010 ◽  
Vol 10 (11) ◽  
pp. 25991-26044
Author(s):  
M. Stock ◽  
Y. F. Cheng ◽  
W. Birmili ◽  
A. Massling ◽  
B. Wehner ◽  
...  
Keyword(s):  
Growth Factors ◽  
Radiative Forcing ◽  
Eastern Mediterranean ◽  
Hygroscopic Growth ◽  
Differential Mobility ◽  
Air Mass ◽  
Air Masses ◽  
Hygroscopic Properties ◽  
Direct Radiative Forcing ◽  
Marine Air

Abstract. This work examines the effect of direct radiative forcing of aerosols in the eastern Mediterranean troposphere as a function of air mass composition, particle size distribution and hygroscopicity, and relative humidity (RH). During intensive field measurements on the island of Crete, Greece, the hygroscopic properties of atmospheric particles were determined using a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) and a Hygroscopicity Differential Mobility Analyzer – Aerodynamic Particle Sizer (H-DMA-APS). Like in several studies before, the H-TDMA identified three hygroscopic sub-fractions of particles in the sub-μm range: a more hygroscopic group, a less hygroscopic group and a nearly hydrophobic particle group. The hygroscopic particle growth factors at 90% RH were a significant function of particle mobility diameter (Dp): 1.42 (± 0.05) at 30 nm compared to 1.63 (± 0.07) at 250 nm. The H-DMA-APS identified up to three hygroscopic sub-fractions at mobility diameters of 1.0 and 1.2 μm. All data recorded between 12 August and 20 October, 2005 were classified into four distinct synoptic-scale air mass types distinguishing between different regions of origin (western Mediterranean vs. the Aegean Sea) as well as the degree of continental pollution (marine vs. continentally influenced). The hygroscopic properties of particles with diameter Dp ≥ 150 nm showed the most pronounced dependency on air mass origin, with growth factors in marine air masses exceeding those in more continentally influenced air masses. Particle size distributions and hygroscopic growth factors were employed to calculate aerosol light scattering coefficients at ambient RH using a Mie model. A main result was the pronounced enhancement of particle scattering over the eastern Mediterranean due to hygroscopic growth, both in the marine and continentally influenced air masses. When RH reached its daytime values around 70–80% in summer, up to 50–70% of the calculated visibility reduction was due to the hygroscopic growth of the particles by water compared to the effect of the dry particles alone. The estimated aerosol direct radiative forcings for both, marine and continentally influenced air masses were negative indicating a net cooling of the atmosphere due to the aerosol. The radiative forcing ΔFr was, nevertheless, dominated by the total aerosol concentration most of the time: ΔFr was typically more negative for continentally influenced aerosols (ca. −4 W m−2) compared to rather clean marine aerosols (ca. −1.5 W m−2). When RH occasionally reached 90% in marine air, ΔFr even reached values down to −7 W m−2. Our results emphasize, on the basis of explicit particle hygroscopicity measurements, the relevance of ambient relative humidity for the radiative forcing of regional atmospheres.

scholarly journals Particle hygroscopicity and its link to chemical composition in the urban atmosphere of Beijing, China, during summertime

2016 ◽  
Vol 16 (2) ◽  
pp. 1123-1138 ◽  
Author(s):  
Z. J. Wu ◽  
J. Zheng ◽  
D. J. Shang ◽  
Z. F. Du ◽  
Y. S. Wu ◽  
...  
Keyword(s):  
Particle Size ◽  
Chemical Composition ◽  
Growth Factor ◽  
Mass Concentration ◽  
Particle Formation ◽  
High Time Resolution ◽  
New Particle Formation ◽  
Hygroscopic Growth ◽  
Hygroscopic Properties ◽  
Beijing China

Abstract. Simultaneous measurements of particle number size distribution, particle hygroscopic properties, and size-resolved chemical composition were made during the summer of 2014 in Beijing, China. During the measurement period, the mean hygroscopicity parameters (κs) of 50, 100, 150, 200, and 250 nm particles were respectively 0.16  ±  0.07, 0.19  ±  0.06, 0.22  ±  0.06, 0.26  ±  0.07, and 0.28  ±  0.10, showing an increasing trend with increasing particle size. Such size dependency of particle hygroscopicity was similar to that of the inorganic mass fraction in PM1. The hydrophilic mode (hygroscopic growth factor, HGF  >  1.2) was more prominent in growth factor probability density distributions and its dominance of hydrophilic mode became more pronounced with increasing particle size. When PM2.5 mass concentration was greater than 50 μg m−3, the fractions of the hydrophilic mode for 150, 250, and 350 nm particles increased towards 1 as PM2.5 mass concentration increased. This indicates that aged particles dominated during severe pollution periods in the atmosphere of Beijing. Particle hygroscopic growth can be well predicted using high-time-resolution size-resolved chemical composition derived from aerosol mass spectrometer (AMS) measurements using the Zdanovskii–Stokes–Robinson (ZSR) mixing rule. The organic hygroscopicity parameter (κorg) showed a positive correlation with the oxygen to carbon ratio. During the new particle formation event associated with strongly active photochemistry, the hygroscopic growth factor or κ of newly formed particles is greater than for particles with the same sizes not during new particle formation (NPF) periods. A quick transformation from external mixture to internal mixture for pre-existing particles (for example, 250 nm particles) was observed. Such transformations may modify the state of the mixture of pre-existing particles and thus modify properties such as the light absorption coefficient and cloud condensation nuclei activation.

scholarly journals Hygroscopic growth of sub-micrometer and one-micrometer aerosol particles measured during ACE-Asia

2007 ◽  
Vol 7 (12) ◽  
pp. 3249-3259 ◽  
Author(s):  
A. Massling ◽  
S. Leinert ◽  
A. Wiedensohler ◽  
D. Covert
Keyword(s):  
Particle Size ◽  
Growth Factors ◽  
Size Range ◽  
Sea Salt ◽  
Dust Particles ◽  
Particle Fraction ◽  
Hygroscopic Growth ◽  
Air Masses ◽  
The One ◽  
Micrometer Size

Abstract. Hygroscopic properties of aerosol particles in the sub-micrometer and one-micrometer size ranges were measured during the ACE-Asia study (Aerosol Characterization Experiment-Asia) in spring 2001. The measurements took place off the coasts of Japan, Korea, and China. All instruments contributing to this study were deployed in a container on the forward deck of the NOAA Research Vessel Ronald H. Brown. Air masses with primarily marine influence and air masses from the Asian continent affected by both anthropogenic sources and by the transport of desert dust aerosol were encountered during the cruise. Results showed very different hygroscopic behavior in the sub-micrometer size range compared to the one-micrometer size range. In general, for all continentally influenced air masses, the one-micrometer particle population was characterized by two different particle groups – a nearly hydrophobic fraction with growth factors around 1.0 representative of dust particles and a sea salt fraction with hygroscopic growth factors around 2.0. The number fraction of dust particles was generally about 60% independent of long-range air mass origin. For sub-micrometer particles, a dominant, more hygroscopic particle fraction with growth factors between 1.5 and 1.9 (depending on dry particle size) consistent with ammonium sulfate or non-neutralized sulfates as major component was always found. In marine air masses and for larger sizes within the sub-micrometer range (Dp=250 and 350 nm), a sea salt fraction with growth factors between 2.0 and 2.1 was also observed. For all other air masses, the more hygroscopic particle fraction in the sub-micrometer size range was mostly accompanied by a less hygroscopic particle fraction with growth factors between 1.20 and 1.55 depending on both the continental sources and the dry particle size. Number fractions of this particle group varied between 4 and 39% depending on dry particle size and air mass type. Nearly hydrophobic particles indicating dust particles in the sub-micrometer size regime were only found for particles with Dp=250 and 350 nm during a time period when the aerosol was influenced by transport from Asian desert regions.

scholarly journals Hygroscopic growth of sub-micrometer and one-micrometer aerosol particles measured during ACE-Asia

2006 ◽  
Vol 6 (6) ◽  
pp. 12267-12300 ◽  
Author(s):  
A. Massling ◽  
S. Leinert ◽  
A. Wiedensohler ◽  
D. Covert
Keyword(s):  
Particle Size ◽  
Growth Factors ◽  
Size Range ◽  
Aerosol Particles ◽  
Dust Particles ◽  
Particle Fraction ◽  
Hygroscopic Growth ◽  
Air Masses ◽  
The One ◽  
Micrometer Size

Abstract. Hygroscopic properties of aerosol particles in the sub-micrometer and one-micrometer size range were measured during the ACE-Asia study (Aerosol Characterization Experiment-Asia) in spring 2001. The measurements took place off the coasts of Japan, Korea, and China. All instruments contributing to this study were deployed in a container on the forward deck of the NOAA Research Vessel Ronald H. Brown. Air masses with primarily marine influence and air masses from the Asian continent affected by both anthropogenic sources and by the transport of desert dust aerosol were encountered during the cruise. Two different systems were used to determine hygroscopic growth of the ambient marine boundary layer aerosol at 90% relative humidity (RH). An H-TDMA-system (Hygroscopicity-Tandem Differential Mobility Analyzer) (Massling et al., 2003) and a newly developed H-DMA-APS-system (Hygroscopicity-Differential Mobility Analyzer-Aerodynamic Particle Sizer) (Leinert and Wiedensohler, 2006) were applied to analyze sub-micrometer and one-micrometer aerosol particles, respectively. Results showed very different hygroscopic behavior in the sub-micrometer size range compared to the one-micrometer size range. In general, for all continentally influenced air masses, the one-micrometer particle population was characterized by two different particle fractions – a nearly hydrophobic fraction with growth factors around 1.0 representative of dust particles and a sea salt fraction with hygroscopic growth factors around 2.0. The number fraction of dust particles was generally about 60% independent of long-range air mass origin. For sub-micrometer particles, a dominant, more hygroscopic particle fraction with growth factors between 1.5 and 1.9 (depending on dry particle size) indicating ammonium sulfate as major component was always found. In marine air masses and for larger sizes within the sub-micrometer range (Dp=250 and 350 nm), a sea salt fraction with growth factors between 2.0 and 2.1 was also observed. For all other air masses, the more hygroscopic particle fraction in the sub-micrometer size range was mostly accompanied by a less hygroscopic particle fraction with growth factors between 1.20 and 1.55 depending on both the continental sources and the dry particle size. Number fractions of this particle group varied between 4 and 39% depending on dry particle size and air mass type. Nearly hydrophobic particles indicating dust particles in the sub-micrometer size regime were only found for particles with Dp=250 and 350 nm during a time period when the aerosol was significantly influenced by transport from Asian desert regions.

scholarly journals Hygroscopicity and chemical composition of Antarctic sub-micrometre aerosol particles and observations of new particle formation

2010 ◽  
Vol 10 (9) ◽  
pp. 4253-4271 ◽  
Author(s):  
E. Asmi ◽  
A. Frey ◽  
A. Virkkula ◽  
M. Ehn ◽  
H. E. Manninen ◽  
...  
Keyword(s):  
Growth Factors ◽  
Southern Ocean ◽  
Volume Fraction ◽  
Particle Formation ◽  
Chemical Data ◽  
Special Focus ◽  
New Particle Formation ◽  
Hygroscopic Growth ◽  
Air Masses ◽  
Hygroscopic Properties

Abstract. The Antarctic near-coastal sub-micrometre aerosol particle features in summer were characterised based on measured data on aerosol hygroscopicity, size distributions, volatility and chemical ion and organic carbon mass concentrations. Hysplit model was used to calculate the history of the air masses to predict the particle origin. Additional measurements of meteorological parameters were utilised. The hygroscopic properties of particles mostly resembled those of marine aerosols. The measurements took place at 130 km from the Southern Ocean, which was the most significant factor affecting the particle properties. This is explained by the lack of additional sources on the continent of Antarctica. The Southern Ocean was thus a likely source of the particles and nucleating and condensing vapours. The particles were very hygroscopic (HGF 1.75 at 90 nm) and very volatile. Most of the sub-100 nm particle volume volatilised below 100 °C. Based on chemical data, particle hygroscopic and volatile properties were explained by a large fraction of non-neutralised sulphuric acid together with organic material. The hygroscopic growth factors assessed from chemical data were similar to measured. Hygroscopicity was higher in dry continental air masses compared with the moist marine air masses. This was explained by the aging of the marine organic species and lower methanesulphonic acid volume fraction together with the changes in the inorganic aerosol chemistry as the aerosol had travelled long time over the continental Antarctica. Special focus was directed in detailed examination of the observed new particle formation events. Indications of the preference of negative over positive ions in nucleation could be detected. However, in a detailed case study, the neutral particles dominated the particle formation process. Freshly nucleated particles had the smallest hygroscopic growth factors, which increased subsequent to particle aging.

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