Dynamic Optical Properties of Tar Balls during Night-time Aging

SHU-WEN YOU, Prabhav Upadhyay, Joshin Kumar, Ganesh Chelluboyina, Payton Beeler, Joseph V. Puthussery, Benjamin Sumlin, Rajan K. Chakrabarty, Washington University in St. Louis

     Abstract Number: 527
     Working Group: Carbonaceous Aerosol

Abstract
Understanding the carbonaceous aerosols emitted from biomass burning (BB) is of great concern pertaining to their effects on climatic forcing. Tar balls (TBs) are a type of organic carbon generated from low-temperature combustion and contribute to ~30% of BB aerosol mass. With the expected increase in BB emissions due to warmer climates, it is important to understand the interplay between formation mechanisms, physicochemical properties, and optical properties. Few studies have systematically addressed the effects of night-time atmospheric processing on TBs optical properties. In this work, we attempt to elucidate the variation of optical properties during night-time aging under controlled laboratory conditions. The TBs used in this study are generated from low-temperature combustion. Potential aerosol mass oxidation flow reactor (PAM-OFR) is used to investigate the effects of the night-time aging process under different levels of nitrate radical (NO₃•) exposures. Integrated-photoacoustic nephelometer (IPN) monitors the absorption and scattering coefficient of TBs across UV, visible, and IR spectrum, providing dynamic optical properties before and after aging processes. Both fresh and NO₃•-aged TBs are collected for further characterizations (morphology, internal structure, water/methanol solubility, OC/EC analyses, and volatility). By connecting the physicochemical properties to the optical properties of TBs, we are able to advance our understanding of TBs formation mechanisms as well as their regional/global climate effects.