Modeled Impact of Deposition on the Oxidation Pathways of Common Reactive Precursors
CHENYANG BI, Gabriel Isaacman-VanWertz,
Virginia Tech Abstract Number: 153
Working Group: Aerosol Chemistry
AbstractReactive organic precursors emitted into the atmosphere may undergo extremely-complex oxidation reactions, produce hundreds of thousands of oxidations products that have a wide range of functionality and reactivity, and significantly impact climate and human health. Consequently, methods to reduce such complexity are needed to interpret the large atmospheric dataset and identify key drivers in atmospheric processes. As one of the attempts to achieve this goal, we consider the fate of a compound in the atmosphere as competition between loss processes, particularly oxidation, which propagates chemistry and may form aerosol, and deposition, which removes reactive carbon from participating in further chemistry. Based on previous estimations of deposition and oxidation timescales of atmospheric reactive organics, we examine the competition between oxidation and deposition and understand the impacts of deposition on the downstream chemistry in the case of the oxidation of common precursors. Timescales for deposition are implemented as first-order processes into a box model to simulate the oxidation of single reactive precursors, such as isoprene and α-pinene, and a mixture of common reactive precursors found in the Southern Oxidant and Aerosol Study (SOAS) campaign. The simulations enabled the quantification of the fraction of oxidant reactivity and formation potential of secondary organic aerosol (SOA) that is removed or prevented by deposition. We prioritize the chemical products in a known cascade of complex oxidation reactions based on three key criteria: 1) compounds having competitive timescales, 2) compounds produced as early-generation products, and 3) compounds having high relative abundance. We demonstrate the importance of the three criteria by quantifying the impacts of those prioritized organics on the aerosol formation potential and total reactivity. We will also discuss the implications of this result for local and regional atmospheric composition.