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Organics alter hygroscopic behavior of atmospheric particles

Saxena, Pradeep and Hildemann, Lynn M. and McMurry, Peter H. and Seinfeld, John H. (1995) Organics alter hygroscopic behavior of atmospheric particles. Journal of Geophysical Research. Atmospheres, 100 (D9). pp. 18755-18770. ISSN 2169-897X. doi:10.1029/95jd01835.

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The optical and chemical properties of atmospheric particles and their ability to act as cloud condensation nuclei (CCN) depend strongly upon their affinity for water. Laboratory experiments have shown that water soluble substances such as ammonium sulfate, ammonium nitrate, and sodium chloride, which are major inorganic components of atmospheric particles, absorb water in an amount proportional to water vapor pressure. Analogous information about the interactions between water and organics, which are another major component of atmospheric particles, is lacking. Here we analyze concurrent observations of particle chemical composition and water content from a continental nonurban (Grand Canyon) and an urban (Los Angeles) location to determine whether the water content of atmospheric particles is influenced by the presence of organics. By comparing the observed water content with the water content expected to be associated with the inorganic fraction, we find that the aggregate hygroscopic properties of inorganic particles are altered substantially when organics are also present. Furthermore, the alterations can be positive or negative. For the nonurban location, organics enhance water absorption by inorganics. In the relative humidity (RH) range of 80–88% organics account for 25–40% of the total water uptake, on average. For the urban location, on the other hand, the net effect of organics is to diminish water absorption of the inorganics by 25–35% in the RH range of 83–93%.

Item Type:Article
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URLURL TypeDescription
Hildemann, Lynn M.0000-0003-4772-915X
Seinfeld, John H.0000-0003-1344-4068
Additional Information:We are grateful to Peter K. Mueller of Electric Power Research Institute (EPRI) for proposing the problem addressed in this paper; to Prabir Burman of University of California, Davis, for helping with the statistical analyses; and to Barbara J. Turpin (formerly at University of Minnesota and now at Rutgers University) for discussing our queries concerning the data used in this work and for critiquing the manuscript. We thank Petros Koutrakis and George Allen of Harvard School of Public Health for HEADS observations and Bart Croes of California Air Resources Board (ARB) for SCAQS data and reports. This work was supported by EPRI. Some of the observations used in this analysis were collected in prior studies with support from the ARB, Coordinated Research Council, U.S. Environmental Protection Agency, Southern California Edison, and Salt River Project.
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Electric Power Research Institute (EPRI)UNSPECIFIED
Issue or Number:D9
Record Number:CaltechAUTHORS:20230226-708566600.1
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:119509
Deposited By: Tony Diaz
Deposited On:28 Feb 2023 17:12
Last Modified:28 Feb 2023 17:12

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