A223-0002
Changes in Light Absorption Driven by Two Different Oxidation Processes on Atmospheric Tar Balls During FIREX-AQ
Wednesday, 16 December 2020
Poster
Benjamin Sumlin1, Edward Fortner2, Andrew T Lambe2, Nishit Shetty3, Pai Liu1, Francesca Majluf2, Scott C. Herndon4 and Rajan Chakrabarty5, (1)Washington University in St Louis, St. Louis, MO, United States, (2)Aerodyne Research Inc., Billerica, MA, United States, (3)Washington University in St Louis, Energy, Environmental, and Chemical Engineering, St. Louis, United States, (4)Aerodyne Research Inc, Billerica, MA, United States, (5)Washington University in Saint Louis, Saint Louis, MO, United States
Abstract:
Wildfire events emit carbonaceous aerosol in great quantities, and these particles drive climate by interacting with sunlight to either cool by scattering or heat by absorption. Organic carbon (OC) aerosol was once thought to be purely scattering; however, we now understand that tar balls, a subset of OC, strongly absorbs sunlight, particularly in the short visible and near-UV wavelengths. There is a growing body of research producing evidence that the light absorption properties of these aerosol are affected by atmospheric processing, including oxidation reactions.
We sampled wildfire plumes in the western United States during FIREX-AQ using a new multiwavelength photoacoustic spectrometer on board the Aerodyne Mobile Laboratory. These plumes were subjected to heterogeneous oxidation using an Aerodyne Potential Aerosol Mass oxidation flow reactor. To capture the impacts of diurnal variations in ambient chemistry, two oxidation mechanisms were used. Daylight-driven oxidation was mimicked by exposing plumes to varying quantities of OH radical, while nighttime processes were mimicked using NO3. Chemical changes in aerosol composition were tracked using an Aerodyne Aerosol Mass Spectrometer.
We present a comparison of the changes to light absorption behavior and mass spectrometry results from these two oxidation processes, and discuss the implications for radiative forcing within the context of previous laboratory findings.
