A234-08
Nitrous acid chemistry in early biomass burning plumes during the FIREX-AQ campaign
Wednesday, 16 December 2020: 07:28
Virtual
Katie Tuite, University of California Los Angeles, Los Angeles, CA, United States, Nathaniel Brockway, University of California Los Angeles, Atmospheric and Oceanic Sciences, Los Angeles, CA, United States, Jennie L Thomas, IGE Institut des Géosciences de l’Environnement, Grenoble, France, Jochen Stutz, University of California Los Angeles, Department of Atmospheric and Oceanic Sciences, Los Angeles, CA, United States and FIREX-AQ team
Abstract:
Biomass burning is one of the largest sources of primary and secondary pollutants to the global atmosphere and has significant impacts to air quality. Formation of secondary pollutants like ozone and secondary organic aerosol is dependent on hydroxyl (OH) radical concentrations within plumes. Nitrous acid (HONO) is thought to be one of the main OH sources in young plumes since it is directly emitted from fires and quickly photolyzes to give OH. HONO can also be formed within plumes, most likely through heterogeneous chemistry on aerosols. Measurements of HONO within plumes are sparse and emission ratios are not well constrained, however, causing uncertainty in HONO’s role in radical formation.
The FIREX-AQ experiment provided an opportunity to study HONO chemistry in biomass burning plumes throughout the United States using both in-situ and remote sensing measurements on board the NASA DC-8 aircraft. UCLA’s airborne Differential Optical Absorption Spectroscopy (DOAS) instrument observed young plumes over the burning area to give emission ratios of HONO, NO2, and HCHO. In addition, in-plume measurements were recorded downwind as the smoke aged. Here we present DOAS remote sensing observations from early plumes with a smoke age of a few hours or less. These observations are used to investigate OH formation rates from HONO and better constrain plume OH budgets. In addition, we will show first results from a one-dimensional model study that can help assess the relative importance of direct emission and secondary formation of HONO to its total concentration.
