Presentation Title

A Temperature Dependent of Brown Carbon Aerosol Formation and Optical Properties

Faculty Mentor

Paula K Hudson, Daniel B Curtis

Start Date

17-11-2018 3:00 PM

End Date

17-11-2018 5:00 PM

Location

CREVELING 5

Session

POSTER 3

Type of Presentation

Poster

Subject Area

behavioral_social_sciences

Abstract

Aerosol particles, solid particles or liquid droplets suspended in Earth’s atmosphere, have an effect on climate through cloud formation or the interaction with light. A particular aerosol type of interest is brown carbon, named for the yellow to dark brown appearance during its formation. Brown carbon has been proposed to form through the reaction of an aldehyde and a nitrogen containing compound. Common reactants used in the laboratory are glyoxal with either glycine or ammonium sulfate. Although the reactants are transparent in color, as brown carbon aerosol particles form, they absorb visible light, causing a shift in aerosol properties from an cooling to warming effect. This study focuses on using glyoxal and glycine as reactants while varying reaction temperature and relative concentrations of the reactants. Ultraviolet/visible (UV/Vis) absorbance spectra, temperature, and pH are measured as a function of time during brown carbon formation over a period of 48 hours. As brown carbon forms, the absorbance from 200-900nm increases over time where the rate of increasing absorbance decreases as a function of time. Results show a positive correlation between brown carbon absorbance and temperature when absorbance rates increase from 0.046 AU/hour to 0.48 AU/hour as temperature increases from 25℃to 60℃. Because the presence of brown carbon aerosol will likely have a warming effect on climate, the increasing rate of formation with increasing temperature will create a positive feedback loop where increasing temperatures will increase the rate of brown carbon aerosol formation which will further increase the temperature. Experiments to determine the effect of initial reactant concentration and pH on brown carbon formation are currently underway.

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Nov 17th, 3:00 PM Nov 17th, 5:00 PM

A Temperature Dependent of Brown Carbon Aerosol Formation and Optical Properties

CREVELING 5

Aerosol particles, solid particles or liquid droplets suspended in Earth’s atmosphere, have an effect on climate through cloud formation or the interaction with light. A particular aerosol type of interest is brown carbon, named for the yellow to dark brown appearance during its formation. Brown carbon has been proposed to form through the reaction of an aldehyde and a nitrogen containing compound. Common reactants used in the laboratory are glyoxal with either glycine or ammonium sulfate. Although the reactants are transparent in color, as brown carbon aerosol particles form, they absorb visible light, causing a shift in aerosol properties from an cooling to warming effect. This study focuses on using glyoxal and glycine as reactants while varying reaction temperature and relative concentrations of the reactants. Ultraviolet/visible (UV/Vis) absorbance spectra, temperature, and pH are measured as a function of time during brown carbon formation over a period of 48 hours. As brown carbon forms, the absorbance from 200-900nm increases over time where the rate of increasing absorbance decreases as a function of time. Results show a positive correlation between brown carbon absorbance and temperature when absorbance rates increase from 0.046 AU/hour to 0.48 AU/hour as temperature increases from 25℃to 60℃. Because the presence of brown carbon aerosol will likely have a warming effect on climate, the increasing rate of formation with increasing temperature will create a positive feedback loop where increasing temperatures will increase the rate of brown carbon aerosol formation which will further increase the temperature. Experiments to determine the effect of initial reactant concentration and pH on brown carbon formation are currently underway.