Optical properties of brown carbon surrogates formed by glyoxal and ammonium sulfate

Kyle J. Zarzana(1, 2, 3) and Margaret A. Tolbert(1, 2)

Abstract
A large fraction of aerosol is composed of organic compounds and understanding how these compounds interact with light is crucial to understanding their role in affecting climate. The bulk of organic aerosol is non-absorbing, but a significant fraction is composed of compounds that absorb at shorter wavelengths. However, the sources of these absorbing compounds, termed brown carbon, are not well understood. One potential source is aqueous phase reactions between small organic molecules such as glyoxal and nitrogen containing species such as ammonium sulfate. In this study we present refractive indices for the glyoxal/ammonium sulfate system as a function of glyoxal concentration at a wavelength of 405 nm. The implications of these values are also discussed.