TY - JOUR
T1 - Estimation of water uptake by organic compounds in submicron aerosols measured during the Southeastern Aerosol and Visibility Study
AU - Dick, William D.
AU - Saxena, Pradeep
AU - McMurry, Peter H.
N1 - Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2000
Y1 - 2000
N2 - In situ measurements of size-dependent water uptake by atmospheric particles made with a tandem differential mobility analyzer (TDMA) and size-resolved chemical composition of aerosol samples collected with cascade impactors in the Smoky Mountains have been examined in order to ascertain the influence of organic carbon compounds on aerosol hygroscopicity. Particles were dried to ∼5% relative humidity (RH) before entering the TDMA, leading us to believe that salts of ammonium and sulfate were in crystalline states for relative humidities below their expected deliquescent points. TDMA-measured water content was found to be in excess of the sulfate-associated water modeled using laboratory data for binary aqueous solutions and the method of Zdanovskii-Stokes-Robinson for multicomponent solutions over a wide range of humidities (RH=5-85%). Furthermore, excess water was observed to increase in proportion to the organic fraction of mass associated with each examined size in the range 0.05 to 0.4 μm. These data are used to obtain an empirical relationship between the amount of water associated with particulate organics and relative humidity. This analysis shows that organic-associated water content is considerably less than that of sulfate compounds, on a volume basis, for high RH, but comparable or greater for low RH. These results are consistent with laboratory data for water absorption by a range of organics vis-à-vis ammonium salts of sulfate.
AB - In situ measurements of size-dependent water uptake by atmospheric particles made with a tandem differential mobility analyzer (TDMA) and size-resolved chemical composition of aerosol samples collected with cascade impactors in the Smoky Mountains have been examined in order to ascertain the influence of organic carbon compounds on aerosol hygroscopicity. Particles were dried to ∼5% relative humidity (RH) before entering the TDMA, leading us to believe that salts of ammonium and sulfate were in crystalline states for relative humidities below their expected deliquescent points. TDMA-measured water content was found to be in excess of the sulfate-associated water modeled using laboratory data for binary aqueous solutions and the method of Zdanovskii-Stokes-Robinson for multicomponent solutions over a wide range of humidities (RH=5-85%). Furthermore, excess water was observed to increase in proportion to the organic fraction of mass associated with each examined size in the range 0.05 to 0.4 μm. These data are used to obtain an empirical relationship between the amount of water associated with particulate organics and relative humidity. This analysis shows that organic-associated water content is considerably less than that of sulfate compounds, on a volume basis, for high RH, but comparable or greater for low RH. These results are consistent with laboratory data for water absorption by a range of organics vis-à-vis ammonium salts of sulfate.
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U2 - 10.1029/1999JD901001
DO - 10.1029/1999JD901001
M3 - Article
AN - SCOPUS:0033785044
SN - 0148-0227
VL - 105
SP - 1471
EP - 1479
JO - Journal of Geophysical Research Atmospheres
JF - Journal of Geophysical Research Atmospheres
IS - D1
M1 - 1999JD901001
ER -