Hygroscopic and phase separation properties of ammonium sulfate/organics/water ternary solutions

Abstract. Atmospheric aerosol particles are often partially or completely composed of inorganic salts, such as ammonium sulfate and sodium chloride, and therefore exhibit hygroscopic properties. Many inorganic salts have well-defined deliquescence and efflorescence points at which they take up and lose water, respectively. Field measurements have shown that atmospheric aerosols are not typically pure inorganic salt, instead, they often also contain organic species. There is ample evidence from laboratory studies that suggests that mixed particles exist in a phase-separated state, with an aqueous inorganic core and organic shell. Although phase separation has not been measured in situ, there is no reason it would not also take place in the atmosphere. Here, we investigate the deliquescence and efflorescence points, phase separation and ability to exchange gas-phase components of mixed organic and inorganic aerosol using a flow tube coupled with FTIR (Fourier transform infrared) spectroscopy. Ammonium sulfate aerosol mixed with organic polyols with different O : C ratios, including 1,4-butanediol, glycerol, 1,2,6-hexanetriol, 1,2-hexanediol, and 1,5-pentanediol have been investigated. Those constituents correspond to materials found in the atmosphere in great abundance and, therefore, particles prepared in this study should mimic atmospheric mixed-phase aerosol particles. Some results of this study tend to be in agreement with previous microscopy experiments, but others, such as phase separation properties of 1,2,6-hexanetriol, do not agree with previous work. Because the particles studied in this experiment are of a smaller size than those used in microscopy studies, the discrepancies found could be a size-related effect.

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Hygroscopic and phase separation properties of ammonium sulfate/organic/water ternary solutions

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-6537-2015 ◽

2015 ◽

Vol 15 (5) ◽

pp. 6537-6566 ◽

Cited By ~ 1

Author(s):

M. A. Zawadowicz ◽

S. R. Proud ◽

S. S. Seppalainen ◽

D. J. Cziczo

Keyword(s):

Phase Separation ◽

Ammonium Sulfate ◽

Atmospheric Aerosols ◽

Inorganic Salt ◽

Aerosol Particles ◽

Field Measurements ◽

Inorganic Salts ◽

Ample Evidence ◽

Hygroscopic Properties ◽

Inorganic Aerosol

Abstract. Atmospheric aerosol particles are often partially or completely composed of inorganic salts, such as ammonium sulfate and sodium chloride, and therefore exhibit hygroscopic properties. Many inorganic salts have well-defined deliquescence and efflorescence points at which they take up and lose water, respectively. Deliquescence and efflorescence of simple inorganic salt particles have been investigated by a variety of methods, such as IR spectroscopy, tandem mobility analysis and electrodynamic balance. Field measurements have shown that atmospheric aerosols are not typically pure inorganic salt, instead they often also contain organic species. There is ample evidence from laboratory studies that suggests that mixed particles exist in a phase-separated state, with an aqueous inorganic core and organic shell. Although phase separation has not been measured in situ, there is no reason it would not also take place in the atmosphere. Many recent studies have focused on microscopy techniques that require deposition of the aerosol on a glass slide, possibly changing its surface properties. Here, we investigate the deliquescence and efflorescence points, phase separation and ability to exchange gas-phase components of mixed organic and inorganic aerosol using a flow tube coupled with FTIR spectroscopy. Ammonium sulfate aerosol mixed with organic polyols with different O : C ratios, including 1,4-butanediol, glycerol, 1,2,6-hexanetriol, 1,2-hexanediol, and 1,5-pentanediol have been investigated. Those constituents correspond to materials found in the atmosphere in great abundance, and therefore, particles prepared in this study should mimic atmospheric mixed phase aerosol particles. The results of this study tend to be in agreement with previous microscopy experiments, with several key differences, which possibly reveal a size-dependent effect on phase separation in organic/inorganic aerosol particles.

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Microscopic Evidence for Phase Separation of Organic Species and Inorganic Salts in Fine Ambient Aerosol Particles

Environmental Science & Technology ◽

10.1021/acs.est.0c02333 ◽

2021 ◽

Vol 55 (4) ◽

pp. 2234-2242

Author(s):

Weijun Li ◽

Lei Liu ◽

Jian Zhang ◽

Liang Xu ◽

Yuanyuan Wang ◽

...

Keyword(s):

Phase Separation ◽

Aerosol Particles ◽

Inorganic Salts ◽

Ambient Aerosol ◽

Organic Species ◽

Microscopic Evidence

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Influence of Collecting Substrates on the Characterization of Hygroscopic Properties of Inorganic Aerosol Particles

Analytical Chemistry ◽

10.1021/ac4042075 ◽

2014 ◽

Vol 86 (5) ◽

pp. 2648-2656 ◽

Cited By ~ 28

Author(s):

Hyo-Jin Eom ◽

Dhrubajyoti Gupta ◽

Xue Li ◽

Hae-Jin Jung ◽

HyeKyeong Kim ◽

...

Keyword(s):

Aerosol Particles ◽

Hygroscopic Properties ◽

Inorganic Aerosol

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Liquid–liquid phase separation in particles containing organics mixed with ammonium sulfate, ammonium bisulfate, ammonium nitrate or sodium chloride

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-11723-2013 ◽

2013 ◽

Vol 13 (23) ◽

pp. 11723-11734 ◽

Cited By ~ 63

Author(s):

Y. You ◽

L. Renbaum-Wolff ◽

A. K. Bertram

Keyword(s):

Phase Separation ◽

Sodium Chloride ◽

Liquid Phase ◽

Relative Humidity ◽

Ammonium Sulfate ◽

Inorganic Salt ◽

Liquid Phase Separation ◽

Inorganic Salts ◽

Organic Species ◽

Liquid Liquid Phase Separation

Abstract. As the relative humidity varies from high to low values in the atmosphere, particles containing organic species and inorganic salts may undergo liquid–liquid phase separation. The majority of the laboratory work on this subject has used ammonium sulfate as the inorganic salt. In the following we studied liquid–liquid phase separation in particles containing organics mixed with the following salts: ammonium sulfate, ammonium bisulfate, ammonium nitrate and sodium chloride. In each experiment one organic was mixed with one inorganic salt and the liquid–liquid phase separation relative humidity (SRH) was determined. Since we studied 23 different organics mixed with four different salts, a total of 92 different particle types were investigated. Out of the 92 types, 49 underwent liquid–liquid phase separation. For all the inorganic salts, liquid–liquid phase separation was never observed when the oxygen-to-carbon elemental ratio (O : C) &geq; 0.8 and was always observed for O : C < 0.5. For 0.5 &leq; O : C < 0.8, the results depended on the salt type. Out of the 23 organic species investigated, the SRH of 20 organics followed the trend: (NH4)2SO4 &geq; NH4HSO4 &geq; NaCl &geq; NH4NO3. This trend is consistent with previous salting out studies and the Hofmeister series. Based on the range of O : C values found in the atmosphere and the current results, liquid–liquid phase separation is likely a frequent occurrence in both marine and non-marine environments.

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Hygroscopic properties of ammonium sulfate aerosol particles mixed with slightly soluble organic compound

Journal of Aerosol Science ◽

10.1016/s0021-8502(98)00385-1 ◽

1998 ◽

Vol 29 ◽

pp. S587-S588 ◽

Cited By ~ 4

Author(s):

K. Ha¨meri ◽

R.J. Charlson ◽

H.-C. Hansson ◽

M. Jacobson

Keyword(s):

Organic Compound ◽

Ammonium Sulfate ◽

Aerosol Particles ◽

Sulfate Aerosol ◽

Hygroscopic Properties

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Review and uncertainty assessment of size-resolved scavenging coefficient formulations for snow scavenging of atmospheric aerosols

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-14823-2013 ◽

2013 ◽

Vol 13 (6) ◽

pp. 14823-14869 ◽

Cited By ~ 1

Author(s):

L. Zhang ◽

X. Wang ◽

M. D. Moran ◽

J. Feng

Keyword(s):

Atmospheric Aerosols ◽

Atmospheric Aerosol ◽

Collection Efficiency ◽

Aerosol Particles ◽

Field Measurements ◽

Cross Sectional ◽

Atmospheric Aerosol Particles ◽

Order Of Magnitude ◽

Snow Particle ◽

Scavenging Coefficient

Abstract. Theoretical parameterizations for the size-resolved scavenging coefficient for atmospheric aerosol particles scavenged by snow (Λsnow) need assumptions regarding (i) snow particle–aerosol particle collection efficiency E, (ii) snow particle size distribution N(Dp), (iii) snow particle terminal velocity VD, and (iv) snow particle cross-sectional area A. Existing formulas for these parameters are reviewed in the present study and uncertainties in Λsnow caused by various combinations of these parameters are assessed. Different formulations of E can cause uncertainties in Λsnow of more than one order of magnitude for all aerosol sizes for typical snowfall intensities. E is the largest source of uncertainty among all the input parameters, similar to rain scavenging of atmospheric aerosols (Λrain) as was found in a previous study by Wang et al. (2010). However, other parameters can also cause significant uncertainties in Λsnow, and the uncertainties from these parameters are much larger than for Λrain. Specifically, different N(Dp) formulations can cause one-order-of-magnitude uncertainties in Λsnow for all aerosol sizes, as is also the case for a combination of uncertainties from both VD and A. In comparison, uncertainties in Λrain from N(Dp) are smaller than a factor of 5 and those from VD are smaller than a factor of 2. Λsnow estimated from one empirical formula generated from field measurements falls in the upper range of, or is slightly higher than, theoretically estimated values. The predicted aerosol concentrations obtained using different Λsnow formulas can differ by a factor of two for just a one-centimeter snowfall (liquid water equivalent of approximately 1 mm). It is likely that, for typical rain and snow event the removal of atmospheric aerosol particles by snow is more effective than removal by rain for equivalent precipitation amounts, although a firm conclusion requires much more evidence.

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A new experimental approach to study the hygroscopic and optical properties of aerosols: application to ammonium sulfate particles

Atmospheric Measurement Techniques ◽

10.5194/amt-7-183-2014 ◽

2014 ◽

Vol 7 (1) ◽

pp. 183-197 ◽

Cited By ~ 18

Author(s):

C. Denjean ◽

P. Formenti ◽

B. Picquet-Varrault ◽

Y. Katrib ◽

E. Pangui ◽

...

Keyword(s):

Particle Size ◽

Optical Properties ◽

Size Distribution ◽

Ammonium Sulfate ◽

Residence Time ◽

Mie Scattering ◽

Continuous Increase ◽

Continuous Growth ◽

Hygroscopic Properties

Abstract. A new methodology for the determination of the changes due to hygroscopic growth with relative humidity of the number size distribution and optical properties of polydispersed aerosols is described. This method uses the simulation chamber CESAM where the hygroscopic properties of polydispersed aerosol particles can be investigated in situ by exposing them to RH ranging from 0 to 100% for approximately 1 h. In situ humidification is used to provide simultaneous information on the RH-dependence of the particle size and the corresponding scattering coefficient (σscat), and that for the entire size distribution. Optical closure studies, based on integrated nephelometer and aethalometer measurements, Mie scattering calculations and measured particle size distributions, can therefore be performed to yield derived parameters such as the complex refractive index (CRI) at λ = 525 nm. The CRI can also be retrieved in the visible spectrum by combining differential mobility analyzer (DMA) and white light aerosol spectrometer (Palas Welas®) measurements. We have applied this methodology to ammonium sulfate particles, which have well known optical and hygroscopic properties. The CRI obtained from the two methods (1.54–1.57) compared favourably to each other and are also in reasonable agreement with the literature values. The particle's growth was compared to values obtained for one selected size of particles (150 nm) with a H-TDMA and the effect of the residence time for particles humidification was investigated. When the humidification was performed in the chamber for a few minutes, a continuous increase of the ammonium sulfate particle's size and σscat was observed from RH values as low as 30% RH. Comparison of the measured and modelled values based on Köhler and Mie theories shows that layers of water are adsorbed on ammonium sulfate particles below the deliquescence point. In contradiction, the particle's growth reported with H-TDMAs showed a prompt deliquescence of ammonium sulfate particles with no continuous growth in size at low RH. These findings highlight the need to allow sufficient time for particle-water vapour equilibrium in investigating the aerosols hygroscopic properties. H-TDMA instruments induce limited residence time for humidification and seem to be insufficient for water adsorption on ammonium sulfate particles.

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Prediction of activity coefficients in liquid aerosol particles containing organic compounds, dissolved inorganic salts, and water—Part 2: Consideration of phase separation effects by an X-UNIFAC model

Atmospheric Environment ◽

10.1016/j.atmosenv.2006.04.031 ◽

2006 ◽

Vol 40 (33) ◽

pp. 6422-6436 ◽

Cited By ~ 61

Author(s):

Elsa I. Chang ◽

James F. Pankow

Keyword(s):

Phase Separation ◽

Organic Compounds ◽

Activity Coefficients ◽

Aerosol Particles ◽

Inorganic Salts ◽

Unifac Model

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Increased inorganic aerosol fraction contributes to air pollution and haze in China

10.5194/acp-2018-968 ◽

2018 ◽

Author(s):

Yonghong Wang ◽

Yuesi Wang ◽

Lili Wang ◽

Tuukka Petäjä ◽

Qiaozhi Zha ◽

...

Keyword(s):

Aerosol Particles ◽

Satellite Observation ◽

Pollution Level ◽

Mass Fractions ◽

Particle Pollution ◽

Aerosol Fraction ◽

Inorganic Aerosol ◽

Haze Days ◽

Reduced Surface

Abstract. The detailed formation mechanism of increased number of haze events in China is still not very clear. Here, we found that reduced surface visibility and an increase in satellite derived columnar concentration of inorganic precursor concentrations are connected with each other. Typically higher inorganic mass fractions lead to increased aerosol water uptake and light scattering ability in elevated relative humidity. Satellite observation of aerosol precursors of NO2 and SO2 showed increased concentrations during study period. Our in-situ measurement of aerosol chemical composition in Beijing also confirmed increased contribution of inorganic aerosol fraction as a function of increased particle pollution level. Our investigations demonstrate that the increased inorganic fraction in the aerosol particles is a key component in the frequently occurring haze days during studying period, and particularly the reduction of nitrate, sulfate and their precursor gases would contribute towards better air quality in China.

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