Keywords

syringic acid aerosol particles; vanillic acid aerosol particles; CCN activity; effective uptake coefficient; ozonolysis

Abstract

In recent years, the incidence of wildfires has considerably increased, with fire seasons starting earlier and ending later than usual due to changes in snowpack, precipitation, and temperature, which are attributed in part to climate change. Wildfires are responsible for the emission of a variety of gases and organic aerosol particles in the atmosphere with profound impacts on air quality, visibility, and human health. The aerosol particles produced by wildfires can contribute to climate change by scattering or absorbing solar radiation, affecting the radiative balance of the planet through cooling or warming effects, or by acting as cloud condensation nuclei (CCN). Phenolic acids aerosol particles are abundant products of biomass burning and have been often used as tracers for the type of biomass burned. Despite their abundance, little is known about their reactivity and CCN activity. Here, we report on the CCN activity of fresh and aged vanillic acid and syringic acid aerosol particles to assess their impact on the mechanism of cloud formation. The reactivity of vanillic acid and syringic acid aerosol particles with ozone and their CCN activity before and after the reaction with ozone is investigated in a flow tube reactor in conjunction with a high-resolution Orbitrap mass spectrometer, a scanning mobility particle sizer, and a CCN counter. An atomizer and an electrostatic classifier are used to produce monodisperse aerosol particles from aqueous solutions of vanillic acid or syringic acid. The monodisperse particles are subsequently injected into the flow tube reactor and exposed to controlled amounts of ozone at a well-defined residence time. Although vanillic acid and syringic acid aerosol particles are found to slowly react with ozone, with effective uptake coefficients in the order of 10-7, the oxidation of both vanillic acid and syringic acid aerosol particles leads to an increase in their CCN activity. For instance, the CCN activity of aged syringic acid aerosol particles was found to be five times higher compared to fresh particles. This study emphasizes the importance of investigating the rate of change in CCN activity of phenolic acids under the combined effects of several atmospheric parameters such as oxidants and relative humidity to accurately describe their role in cloud formation.

Thesis Completion Year

2025

Thesis Completion Semester

Spring

Thesis Chair

Popolan-Vaida, Denisia M.

College

College of Sciences

Department

Chemistry

Thesis Discipline

Chemistry

Language

English

Access Status

Open Access

Length of Campus Access

None

Campus Location

Orlando (Main) Campus

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Rights Statement

In Copyright