AAAR 38th Annual Conference
October 5 - October 9, 2020
Virtual Conference
Aerosol in the atmosphere undergo a myriad of physical and chemical transformations and impact their surrounding environment in various ways. Aerosol particles containing brown carbon chromophores absorb solar radiation, leading to warming of their surroundings that may impact their role as cloud condensation nuclei. It is important to determine the physical and optical properties of brown carbon aerosol in order to more fully understand their role in the atmosphere.
In this work, a linear quadrupole electrodynamic balance with a broadband light source is used to illuminate suspended brown carbon droplets for Mie resonance spectroscopy. The back-scattered light is measured, and morphology dependent resonances are used to ascertain the size, refractive index, and dispersion properties. Brown carbon is strongly absorbing at shorter wavelengths (<450 nm) but less so at long wavelengths (>600nm), allowing resonance spectra to be measured in both absorbing and non-absorbing regions using a broadband illumination. From these data, we explore the hygroscopic growth and light scattering behavior of three soluble brown carbon components suspended in aqueous droplets: 4-nitrocatechol, 4-nitrobenzoic acid, and 4-nitrophenol.