Phase Transformation and Metastability of Hygroscopic Microparticles

Tang, I.N.; Fung, K. H.; Imre, Dan G.; Munkelwitz, H.R.

doi:10.1080/02786829508965327

Cited by 135 publications

(134 citation statements)

References 24 publications

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“…The hygroscopic properties of (NH 4 ) 2 SO 4 have been well understood and characterized by several different techniques Munkelwitz, 1993, 1994;Tang et al, 1995;Cziczo et al, 1997;Onasch et al, 1999;Gysel et al, 2002), and thus making it an ideal system to test the H-TDMA system. Fig.…”

Section: Resultsmentioning

confidence: 99%

Hygroscopicity of Inorganic Aerosols: Size and Relative Humidity Effects on the Growth Factor

Qiao

Chen

et al. 2010

Aerosol Air Qual. Res.

105

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The hygroscopic properties of inorganic salt particles, including (NH 4 ) 2 SO 4 , NaCl, Na 2 SO 4 and NaNO 3 , are investigated using a self-assembled hygroscopic tandem differential mobility analyzer (H-TDMA) system. The iso-GF (growth factor) curves are derived to illustrate the effects of the initial particle size (D 0 ) and relative humidity (RH) on the GFs. For those salt particles of 100 nm, the GFs measured agreed well with their theoretical Köhler curves. In the size range of 20-200 nm, the GFs of (NH 4 ) 2 SO 4 , NaCl and Na 2 SO 4 particles all continuously decrease with D 0 increasing below the deliquescence RH (DRH). However, when RH is higher than the DRH, the GFs of those salts aerosols increase with D 0 throughout the investigated size range. Similar increase trend of GFs with D 0 is also observed for NaNO 3 aerosols though they do not exhibit the abrupt deliquescence behavior. From iso-GF curves, it can be clearly observed that the GFs of (NH 4 ) 2 SO4, NaCl and Na 2 SO 4 particles all increase with the RH while the values decrease with D 0 below DRH. And above DRH, the GFs are more sensitive to D 0 for particles smaller than 60 nm, while the GFs are more sensitive to RH for particles larger than 80 nm. For NaNO 3 aerosols, the iso-GF curves indicate the size-effect becomes more prominent on their hygroscopicity as the RH increases. The iso-GF curves provide a lucid and explicit insight into the hygroscopic growth of salts particles. Through iso-GF curves, we can clearly elucidate the major factor that affects the ultimate particle diameter at ambient atmosphere.

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Section: Resultsmentioning

confidence: 99%

Hygroscopicity of Inorganic Aerosols: Size and Relative Humidity Effects on the Growth Factor

Qiao

Chen

et al. 2010

Aerosol Air Qual. Res.

105

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“…Since solution droplets tend to become highly supersaturated before efflorescence, the resulting solid may be in a metastable state that is not predicted from the bulk-phase thermodynamic equilibrium. In fact, some solid metastable states formed in hygroscopic particles may not even exist in the bulk phase (Tang et al, 1995). It follows that the hydration properties of hygroscopic aerosol particles can not always be predicted from their bulksolution properties.…”

Section: Hydration Behavior and Metastabilitymentioning

confidence: 96%

Phase Transformation and Growth of Hygroscopic Aerosols

Tang¹

2000

Aerosol Chemical Processes in the Environment

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DISCLAIMERPortions of this document may be illegible in electronic image products. Images are produced from the best available original document. AbstractAmbient aerosols frequently contain large portions of hygroscopic inorganic salts such as chlorides, nitrates, and sulfates in either pure or mixed forms. Such inorganic salt aerosols exhibit the properties of deliquescence and efflorescence in air. The phase transformation from a solid particle to a saline droplet usually occurs spontaneously when the relative humidity of the atmosphere reaches a level specific to the chemical composition of the aerosol particle. Conversely, when the relative humidity decreases and becomes low enough, the saline droplet will evaporate and suddenly crystallize, expelling all its water content. The phase transformation and growth of aerosols play an important role in many atmospheric processes affecting air quality, visibility degradation, and climate changes. In this chapter, an exposition of the underlying thermodynamic principles is given, and recent advances in experimental methods utilizing singleparticle levitation are discussed. In addition, pertinent and available thermodynamic data, which are needed for predicting the deliquescence properties of single and multi-component aerosols, are compiled. This chapter is useful to research scientists who are either interested in pursuing further studies of aerosol thermodynamics, or required to model the dynamic behavior of hygroscopic aerosols in a humid environment.

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“…Several laboratory and field studies have given attention to the relative humidity (RH) at which solid particles liquefy (deliquescence point), and the RH at which liquid particles form solids (crystallization point), because the phase (wet or dry) of the atmospheric aerosol particles can affect both their optical and radiative properties and gas-aerosol reactions Kim and Seinfeld, 1993;Tang et al 1995;Dougle et al, 1998 are difficult to form (Cizczo et al, 1997). Pure ammonium nitrate deliquesces at 62 % RH (298 K), but laboratory experiments show that they don't reach crystallization point also at 8 % RH (Dougle et al, 1998).…”

Section: Temporal Variationmentioning

confidence: 99%

Chemical characteristics of inorganic ammonium salts in PM<sub>2.5</sub> in the atmosphere of Beijing (China)

et al. 2011

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Abstract. The atmospheric concentrations of gaseous HNO 3 , HCl and NH 3 and their relative salts have been measured during two field campaigns in the winter and in the summer of 2007 at Beijing (China), as part of CARE-BEIJING (Campaigns of Air Quality Research in Beijing and Surrounding Region). In this study, annular denuder technique used with integration times of 2 and 24h to collect inorganic and soluble PM 2.5 without interferences from gas-particle and particle-particle interactions. The results were discussed from the standpoint of temporal and diurnal variations and meteorological effects. Fine particulate Cl − , NH 4 were higher during summer (12.30 µg m −3 and 18.24 µg m −3 , respectively) than during winter (6.51 µg m −3 and 7.50 µg m −3 , respectively). Daily mean concentrations of fine particulate Cl − were higher during winter (2.94 µg m −3 ) than during summer (0.79 µg m −3 ), while fine particulate NO − 3 showed similar both in winter (8.38 µg m −3 ) and in summer (9.62 µg m −3 ) periods. The presence of large amounts of fine particulate NO − 3 even in summer are due to higher local and regional concentrations of NH 3 in the atmosphere available to neutralize H 2 SO 4 and HNO 3 , which is consistent with the observation that the measured particulate species were neutralized. The composition of fine particulate matter indicated the domination of (NH 4 ) 2 SO 4 during winter and summer periods. In addition, the high relative humidity conditions in summer periodCorrespondence to: A. Ianniello (ianniello@iia.cnr.it) seemed to dissolve a significant fraction of HNO 3 and NH 3 enhancing fine particulate NO − 3 and NH + 4 in the atmosphere. All measured particulate species showed diurnal similar patterns during the winter and summer periods with higher peaks in the early morning, especially in summer, when humid and stable atmospheric conditions occurred. These diurnal variations were affected by wind direction suggesting regional and local source influences. The fine particulate species were correlated with NO x and PM 2.5 , supporting the hypothesis that traffic may be also an important source of secondary particles.

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Phase Transformation and Metastability of Hygroscopic Microparticles

Cited by 135 publications

References 24 publications

Hygroscopicity of Inorganic Aerosols: Size and Relative Humidity Effects on the Growth Factor

Hygroscopicity of Inorganic Aerosols: Size and Relative Humidity Effects on the Growth Factor

Phase Transformation and Growth of Hygroscopic Aerosols

Chemical characteristics of inorganic ammonium salts in PM<sub>2.5</sub> in the atmosphere of Beijing (China)

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Phase Transformation and Metastability of Hygroscopic Microparticles

Cited by 135 publications

References 24 publications

Hygroscopicity of Inorganic Aerosols: Size and Relative Humidity Effects on the Growth Factor

Hygroscopicity of Inorganic Aerosols: Size and Relative Humidity Effects on the Growth Factor

Phase Transformation and Growth of Hygroscopic Aerosols

Chemical characteristics of inorganic ammonium salts in PM&lt;sub&gt;2.5&lt;/sub&gt; in the atmosphere of Beijing (China)

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Chemical characteristics of inorganic ammonium salts in PM<sub>2.5</sub> in the atmosphere of Beijing (China)