10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Comprehensive Chemical Characterization of Brown Carbon Aerosols
Peng Lin, Lauren Fleming, Ying Li, Wing-Sy DeRieux, Julia Laskin, Manabu Shiraiwa, Sergey Nizkorodov, ALEXANDER LASKIN, Purdue University
Abstract Number: 1069 Working Group: Carbonaceous Aerosol
Abstract Atmospheric Brown carbon (BrC) is a significant contributor to climate forcing. Understanding the climate effects of BrC, its sources, formation, and atmospheric aging mechanisms requires molecular identification of BrC chromophores and characterization of their light-absorption properties. Herein, we demonstrate an analytical method, which combines high performance liquid chromatography with three different detection technologies to comprehensively investigate UV/vis absorption spectra, chemical composition, and mass absorption coefficients of the individual chromophores in BrC aerosols. We highlight the applications of this methodology for the analysis of BrC in the samples collected from selected source emissions as well as ambient aerosols. The results show that BrC contains organic compounds of diverse molecular structures, polarities, and volatilities. Understanding their molecular identity requires multi-modal application of complementary ionization techniques in combination with high-resolution mass spectrometry. We demonstrate that optical properties of BrC and chemical composition of its chromophores depend significantly on the type of sources. The contributions to light absorption from different classes of chromophores such as aromatic carboxylic acids, nitro-phenols, polycyclic aromatic hydrocarbons (PAHs), and substituted PAHs are quantified, and their mass absorption coefficients are calculated. In addition, molecular speciation of aerosol components is used to estimate glass transition temperatures of individual components and viscosity of the resulting aerosol. The glass transition temperatures for BrC ranged from 254 - 286 K, suggesting that these particles may adopt an amorphous semisolid state at moderate relative humidity.