Investigation of the optical properties of secondary organic aerosols generated from hydrocarbon ozonolysis

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Title: Investigation of the optical properties of secondary organic aerosols generated from hydrocarbon ozonolysis
Author: Redmond, Haley E.
Abstract: This thesis describes and evaluates a simple scheme by which the refractive index (at 589 nm ) of non -absorbing components common to secondary organic aerosols (SOA ) may be predicted from molecular formula and density (g / cm3 ) . The QSPR approach described is based on three parameters linked to refractive index – molecular polarizability , the ratio of mass density to molecular weight , and degree of unsaturation . After computing these quantities for a training set of 111 compounds common to atmospheric aerosols , multi -linear regression analysis was conducted to establish a quantitative relationship between the parameters and accepted value of refractive index . The resulting quantitative relationship can often estimate refractive index to ± 0 .01 when averaged across a variety of compound classes . A notable exception is for alcohols for which the model consistently underestimates refractive index . Homogenous internal mixtures can conceivably be addressed through use of either the volume or mole fraction mixing rules commonly used in the aerosol community . Predicted refractive indices reconstructed from composition data presented in the literature generally agree with previous reports of SOA refractive index . Additionally , the predicted refractive indices lie near measured values we report for SOA generated from vapors of α -pinene and toluene provided the concentration of the precursor hydrocarbon is low . This method may find use in reconstructing optical scattering of organic aerosols if mass composition data is known . Alternatively , the method described could be incorporated into in models of organic aerosol formation / phase partitioning to better constrain organic aerosol optical properties .
URI: http : / /hdl .handle .net /2346 /ETD -TTU -2011 -05 -1457
Date: 2011-05

Citation

Investigation of the optical properties of secondary organic aerosols generated from hydrocarbon ozonolysis. Master's thesis, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /ETD -TTU -2011 -05 -1457 .

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