Brown carbon (BrC) is a class of dark colored compounds found in aerosols that absorb sunlight and contribute to positive radiative forcing and thus global climate change. BrC is formed by the oxidation of organic material, which creates carbonyl precursors that react with other nitrogen containing inorganic compounds commonly found in aerosol, such as ammonium ions or amines. Identification of minor products in the creation of BrC is essential to discover the major contributors to the high molar absorption coefficients in BrC. In this work, computational methods were utilized to characterize the highly absorbing species in BrC, in combination with supercritical fluid chromatography-mass spectrometry (SFC-MS) and ultraviolet-visible (UV-vis) spectroscopy experiments. Density functional theory (DFT) and time-dependent DFT (TD-DFT) were used to determine the contribution of proposed products to the experimental UV-vis absorption spectra and to investigate the reaction mechanisms involved the creation of these BrC species. The results of this work provide key molecular-level insights related to the formation and propagation of BrC species in aerosols.

Density functional theory investigation of brown carbon species in aqueous aerosol mimics

2019 Spring National Meeting

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