Abstract View
Optical Properties of Brown Carbon Aerosol in Levitated Droplets
CHELSEA PRICE, James F. Davies, University of California Riverside
Abstract Number: 92
Working Group: Aerosol Chemistry
Abstract
Widespread wildfires and biomass burning release aerosol particles containing brown carbon into the atmosphere. These aerosol undergo physical and chemical transformations that influence their effects in the environment. Brown carbon chromophores absorb solar radiation and contribute to atmospheric warming, and may also act as cloud condensation nuclei due to the presence of hygroscopic material. Knowledge of the physical and optical properties of brown carbon aerosol as a function of relative humidity (RH) is limited and needs to be further studied to thoroughly understand their role in the atmosphere.
In this work, a linear quadrupole electrodynamic balance with a broadband light source is used to illuminate suspended aqueous brown carbon particles for Mie resonance spectroscopy. The back scattered light from the particle is then used to determine the size, refractive index, and dispersion properties simultaneously. The broadband light source spans 420-680 nm allowing higher wavelengths (non-absorbing region) to be used for sizing and lower wavelengths (absorbing region) to explore light-absorbing properties. From these methods, we measure the hygroscopic growth and optical properties of pure 4-nitrocatechol (4NC) as well as mixtures of 4NC containing a non-absorbing inorganic component (ammonium sulfate) over a range of mixing ratios. These methods can be applied to other brown carbon species to further classify their hygroscopic and optical properties in order to understand their complex interactions in the environment.