Presentation Title

Hygroscopicity of brown carbon aerosol particles: implication for cloud formation

Faculty Mentor

Paula K Hudson

Start Date

17-11-2018 12:30 PM

End Date

17-11-2018 2:30 PM

Location

CREVELING 6

Session

POSTER 2

Type of Presentation

Poster

Subject Area

physical_mathematical_sciences

Abstract

Aerosol particles are liquid or solid particles found in the atmosphere that originate from natural or anthropogenic (man-made) sources. The composition of aerosol particles can play a significant role in cloud formation: the type of cloud formed and the resulting effect on climate. For example, white clouds, made up of a large number of small droplets, reflect solar radiation and have a cooling effect, whereas dark clouds, made up of a small number of large droplets, have a smaller climate effect. One class of aerosol particles of interest is brown carbon (BrC), a key particulate product from biomass burning events. BrC aerosol form through the reaction of an aldehyde and a nitrogen containing compound emitted during fires and, therefore, have highly variable composition. To better understand the role of BrC aerosol in cloud formation, and ultimately, the effect on climate, the hygroscopicity (water uptake) was measured using a quartz crystal microbalance (QCM). Brown carbon aerosol particles generated by reacting glyoxal (GX) and ammonium sulfate (AS) in varying concentrations, were deposited on the quartz crystal, dried, then exposed to increasing relative humidity (RH). The measured deliquescence relative humidity (DRH), the relative humidity at which the solid particles change to aqueous droplets, is strongly dependent on the relative ratio of reactants and the total concentration. The DRH of BrC reaction mixtures is lower than either of the individual reactants (DRHAS = 82% and DRHGX = 68%) and reaches a minimum when the relative concentration of glyoxal is twice that of ammonium sulfate (DRH2GX:1AS = 55%). When the relative ratio of GX or AS is increased, the DRH increases (DRH1GX:2AS = 62% and DRH2GX:0.1AS = 59%). These results suggest that as BrC forms from the initial reactants, aerosol hygroscopicity increases resulting in the formation of white clouds and a cooling effect on climate.

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Nov 17th, 12:30 PM Nov 17th, 2:30 PM

Hygroscopicity of brown carbon aerosol particles: implication for cloud formation

CREVELING 6

Aerosol particles are liquid or solid particles found in the atmosphere that originate from natural or anthropogenic (man-made) sources. The composition of aerosol particles can play a significant role in cloud formation: the type of cloud formed and the resulting effect on climate. For example, white clouds, made up of a large number of small droplets, reflect solar radiation and have a cooling effect, whereas dark clouds, made up of a small number of large droplets, have a smaller climate effect. One class of aerosol particles of interest is brown carbon (BrC), a key particulate product from biomass burning events. BrC aerosol form through the reaction of an aldehyde and a nitrogen containing compound emitted during fires and, therefore, have highly variable composition. To better understand the role of BrC aerosol in cloud formation, and ultimately, the effect on climate, the hygroscopicity (water uptake) was measured using a quartz crystal microbalance (QCM). Brown carbon aerosol particles generated by reacting glyoxal (GX) and ammonium sulfate (AS) in varying concentrations, were deposited on the quartz crystal, dried, then exposed to increasing relative humidity (RH). The measured deliquescence relative humidity (DRH), the relative humidity at which the solid particles change to aqueous droplets, is strongly dependent on the relative ratio of reactants and the total concentration. The DRH of BrC reaction mixtures is lower than either of the individual reactants (DRHAS = 82% and DRHGX = 68%) and reaches a minimum when the relative concentration of glyoxal is twice that of ammonium sulfate (DRH2GX:1AS = 55%). When the relative ratio of GX or AS is increased, the DRH increases (DRH1GX:2AS = 62% and DRH2GX:0.1AS = 59%). These results suggest that as BrC forms from the initial reactants, aerosol hygroscopicity increases resulting in the formation of white clouds and a cooling effect on climate.