Physical and Chemical Properties of Laboratory and Ambient Aerosols Related to Climate Change
Kus, Pinar
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https://hdl.handle.net/2142/83217
Description
Title
Physical and Chemical Properties of Laboratory and Ambient Aerosols Related to Climate Change
Author(s)
Kus, Pinar
Issue Date
2003
Doctoral Committee Chair(s)
Rood, Mark J.
Department of Study
Civl and Environmental Engineering
Discipline
Civl and Environmental Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Environmental
Language
eng
Abstract
This study summarizes the evaluation of closure when measuring and modeling aerosol optical properties as a function of RH in a laboratory and reports measured ambient aerosol optical and chemical properties for an anthropogenically perturbed continental US site from 1995 to 2000. The optical closure experiment was completed in a laboratory set-up for NaCl, (NH4)2SO 4 and NH4NO3 aerosol using an RH scanning nephelometry system. Correcting for nephelometer non-idealities and RH of the sample improved the agreement between measured and predicted total scattering coefficients (sigmasp) at RH = 80% from 35% to 11%. The closure experiment revealed the importance of keeping the nephelometry system isothermal when measuring particle scattering coefficients as a function of RH or as particles exist in the ambient environment. Corrections based on the laboratory results were applied to ambient optical measurements. The averaged hygroscopic growth factor (f(RH = 82%)) at 550 nm was 1.74 +/- 0.31 for sub-micrometer particles for the site. Chemical analysis of submicrometer particles revealed that approximately 50% of the ambient aerosol mass was SO4 and NH4. Direct aerosol radiative forcing (DARF) for the site was estimated to be -1.3 W/m2 at an ambient RH of 72%. Therefore the net effect of ambient aerosols at the site is to cool the atmosphere.
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