Analysis of Mass Absorption Coefficients (MAC) of Selected Anthropogenic Secondary Organic Aerosols extracted using Selected Solvents

Aditya Iyengar, University of California, Irvine

Abstract

Secondary organic aerosols (SOA) result from atmospheric reactions characterized by aqueous-phase or gas-phase oxidation of volatile organic compounds (Romonosky et. al. 2015), and have important health and environmental implications. This particular study focus on comparing the mass absorption coefficients (MAC) of SOAs formed from the oxidation of three anthropogenic VOCs. The chemicals used were three VOCs: benzene, toluene, and p-xylene. The three solvents used were nanopure water, acetonitrile, and methanol. This work is one part of a longer study aimed to test the assumption that many atmospheric scientists routinely use: the absorption coefficients measured in dilute solutions of SOA-extracts are representative of the actual absorption coefficients of SOA in their natural, highly viscous state. This study focuses on testing this assumption. In this study, the procedure involved individually oxidizing the VOC, extracting each oxidized VOC in a solvent, obtaining the absorption spectrum of the extracted SOA, and the calculating the MAC. The procedure was repeated until each oxidized VOC had been individually extracted using each solvent. The results were interesting and thus far indicate that the choice of solvent does not significantly impact the absorbance spectra of the diluted SOA. Even more intriguing, different diluted SOA tend to produce similar spectra when dissolved in the same solvent. The results of this study will help determine if using extractions to study SOA is as reliable a method as it is currently assumed to be. The study is important since it will offer information on, impact, and shape the experimental methods currently employed in the realm of atmospheric aerosol research.

 
Nov 12th, 4:00 PM Nov 12th, 5:00 PM

Analysis of Mass Absorption Coefficients (MAC) of Selected Anthropogenic Secondary Organic Aerosols extracted using Selected Solvents

HUB 302-#97

Secondary organic aerosols (SOA) result from atmospheric reactions characterized by aqueous-phase or gas-phase oxidation of volatile organic compounds (Romonosky et. al. 2015), and have important health and environmental implications. This particular study focus on comparing the mass absorption coefficients (MAC) of SOAs formed from the oxidation of three anthropogenic VOCs. The chemicals used were three VOCs: benzene, toluene, and p-xylene. The three solvents used were nanopure water, acetonitrile, and methanol. This work is one part of a longer study aimed to test the assumption that many atmospheric scientists routinely use: the absorption coefficients measured in dilute solutions of SOA-extracts are representative of the actual absorption coefficients of SOA in their natural, highly viscous state. This study focuses on testing this assumption. In this study, the procedure involved individually oxidizing the VOC, extracting each oxidized VOC in a solvent, obtaining the absorption spectrum of the extracted SOA, and the calculating the MAC. The procedure was repeated until each oxidized VOC had been individually extracted using each solvent. The results were interesting and thus far indicate that the choice of solvent does not significantly impact the absorbance spectra of the diluted SOA. Even more intriguing, different diluted SOA tend to produce similar spectra when dissolved in the same solvent. The results of this study will help determine if using extractions to study SOA is as reliable a method as it is currently assumed to be. The study is important since it will offer information on, impact, and shape the experimental methods currently employed in the realm of atmospheric aerosol research.