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The Influence of Formation Temperatu...

Smith, Katherine.

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The Influence of Formation Temperature on Secondary Organic Aerosol Volatility.

Record Type:	Electronic resources : Monograph/item
Title/Author:	The Influence of Formation Temperature on Secondary Organic Aerosol Volatility./
Author:	Smith, Katherine.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2018,
Description:	39 p.
Notes:	Source: Masters Abstracts International, Volume: 57-05.
Contained By:	Masters Abstracts International57-05(E).
Subject:	Environmental engineering. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10687734
ISBN:	9780355967500

The Influence of Formation Temperature on Secondary Organic Aerosol Volatility.
Smith, Katherine.

The Influence of Formation Temperature on Secondary Organic Aerosol Volatility. - Ann Arbor : ProQuest Dissertations & Theses, 2018 - 39 p.

Source: Masters Abstracts International, Volume: 57-05.

Thesis (M.S.)--University of California, Davis, 2018.

The volatility of secondary organic aerosol (SOA) formed from the dark ozonolysis of alpha-pinene in a flow tube at temperatures ranging from 275 to 298 K has been characterized by thermally induced evaporation. The SOA was heated from the formation temperature (Tf) in a thermodenuder and the temperature-dependent volume loss was measured. The resulting thermograms for the SOA formed at the different temperatures were nearly identical when considered as a function of DeltaT (= T -- Tf), rather than absolute temperature. A kinetic model of aerosol evaporation was used to derive Tf-specific effective volatility distributions for the SOA. The derived distributions indicate SOA formed at lower temperatures is composed of compounds having higher effective volatilities compared to that formed at higher temperatures. However, the increased abundance of compounds having higher effective volatilities at lower Tf cannot be explained solely due to increased partitioning into the particle phase due to a decrease in vapor pressures. Instead, much of the dependence on Tf likely results from T-dependent changes in the fraction of the particles that is monomers versus dimers (or higher order oligomers). The relatively short formation time (<1 min) appears to have prohibited the system from reaching equilibrium with respect to the monomer-dimer distribution in the condensed phase. While dimer formation is more thermodynamically favorable at lower temperatures, the increased rate of dimer formation at higher temperatures led to the dimer fraction being larger. Because dimers are less volatile than monomers, the increased dimer fraction at higher Tf leads to the SOA appearing to be less volatile and helps to explain the differences in volatility distributions between different formation temperatures. These observations provide further evidence that dimer formation within alpha-pinene SOA occurs on short timescales and indicates that the temperature dependence of SOA volatility depends on dimer formation kinetic.

ISBN: 9780355967500Subjects--Topical Terms:

548583
Environmental engineering.

The Influence of Formation Temperature on Secondary Organic Aerosol Volatility.
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500 $a Source: Masters Abstracts International, Volume: 57-05.
500 $a Adviser: Christopher D. Cappa.
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520 $a The volatility of secondary organic aerosol (SOA) formed from the dark ozonolysis of alpha-pinene in a flow tube at temperatures ranging from 275 to 298 K has been characterized by thermally induced evaporation. The SOA was heated from the formation temperature (Tf) in a thermodenuder and the temperature-dependent volume loss was measured. The resulting thermograms for the SOA formed at the different temperatures were nearly identical when considered as a function of DeltaT (= T -- Tf), rather than absolute temperature. A kinetic model of aerosol evaporation was used to derive Tf-specific effective volatility distributions for the SOA. The derived distributions indicate SOA formed at lower temperatures is composed of compounds having higher effective volatilities compared to that formed at higher temperatures. However, the increased abundance of compounds having higher effective volatilities at lower Tf cannot be explained solely due to increased partitioning into the particle phase due to a decrease in vapor pressures. Instead, much of the dependence on Tf likely results from T-dependent changes in the fraction of the particles that is monomers versus dimers (or higher order oligomers). The relatively short formation time (<1 min) appears to have prohibited the system from reaching equilibrium with respect to the monomer-dimer distribution in the condensed phase. While dimer formation is more thermodynamically favorable at lower temperatures, the increased rate of dimer formation at higher temperatures led to the dimer fraction being larger. Because dimers are less volatile than monomers, the increased dimer fraction at higher Tf leads to the SOA appearing to be less volatile and helps to explain the differences in volatility distributions between different formation temperatures. These observations provide further evidence that dimer formation within alpha-pinene SOA occurs on short timescales and indicates that the temperature dependence of SOA volatility depends on dimer formation kinetic.
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