Water Uptake by NaCl Particles Prior to Deliquescence and the Phase Rule

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Water Uptake by NaCl Particles Prior to Deliquescence and the Phase Rule

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dc.contributor.author Martin, Scot
dc.contributor.author Buseck, Peter R.
dc.contributor.author Russell, Lynn M.
dc.contributor.author Wise, Matthew E.
dc.date.accessioned 2009-08-04T17:52:16Z
dc.date.issued 2008
dc.identifier.citation Wise, Matthew E., Scot T. Martin, Lynn M. Russell, and Peter R. Buseck. 2008. Water uptake by NaCl particles prior to deliquescence and the phase rule. Aerosol Science and Technology 42, no. 4: 281-294. en
dc.identifier.issn 1521-7388 en
dc.identifier.issn 0278-6826 en
dc.identifier.uri http://nrs.harvard.edu/urn-3:HUL.InstRepos:3203273
dc.description.abstract Using an environmental transmission electron microscope (ETEM), we show that a significant amount of water, far exceeding the multilayers caused by surface adsorption, is reversibly associated prior to deliquescence with substrate-supported NaCl particles (dry diameters of ∼ 40 nm to 1.5 μ m; ∼ 18°C). We hypothesize that the water is present as an aqueous solution containing dissolved Na and Cl ions. Water uptake occurs at relative humidities (RH) as low as 70%, and the resulting liquid layer coating the particles is stable over extended times if the RH is held constant. We exposed CaSO<sub>4</sub> and CaSO<sub>4</sub> · 2H<sub>2</sub>O particles to elevated RH values in the ETEM to show that chemically nonspecific condensation of gas-phase water on the TEM substrate does not explain our observations. Furthermore, damage to the NaCl surface induced by the electron beam and small fluctuations in RH do not seem to contribute to or otherwise affect water uptake. We have similar observations of water association for other alkali halide particles, including NaBr and CsCl, prior to deliquescence. To explain the observations, we derive the phase rule for this geometry and show that it allows for the coexistence of liquid, solid, and vapor for the binary NaCl/H<sub>2</sub>O system across a range of RH values. The derivation includes the effects of heterogeneous pressure because of the Laplace-Young relations for the subsystems. Furthermore, in view of the lever rule and the absence of similar observations for free-floating pure NaCl aerosol particles, we hypothesize that the surface energy necessary to support these effects is provided by sample-substrate interactions. Thus, the results of this study may be relevant to atmospheric systems in which soluble compounds are associated with insoluble materials. en
dc.description.sponsorship Engineering and Applied Sciences en
dc.language.iso en_US en
dc.publisher Taylor & Francis en
dc.relation.isversionof http://dx.doi.org/10.1080/02786820802047115 en
dc.relation.hasversion http://www.seas.harvard.edu/environmental-chemistry/index.php?select=3 en
dash.license META_ONLY
dc.title Water Uptake by NaCl Particles Prior to Deliquescence and the Phase Rule en
dc.relation.journal Aerosol Science and Technology en
dash.depositing.author Martin, Scot
dash.embargo.until 10000-01-01

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  • FAS Scholarly Articles [7219]
    Peer reviewed scholarly articles from the Faculty of Arts and Sciences of Harvard University

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