Modeled Impact of Deposition on the Oxidation Pathways of Common Reactive Precursors

GABRIEL ISAACMAN-VANWERTZ, Chenyang Bi, Virginia Tech

     Abstract Number: 377
     Working Group: Aerosol Chemistry

Abstract
The fate of a compound in the atmosphere can be considered 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. The physicochemical properties of modeled and measured atmospheric oxidation products can be used to estimate timescales for these processes. We have previously shown that a substantial fraction of atmospheric organic carbon has competitive timescales for oxidation and deposition, particularly in the case of semi-volatile oxygenated gases that are likely to form aerosol upon further oxidation. We use these timescales here to examine the impacts of deposition on the downstream chemistry in the case of the oxidation of common precursors. Timescales for dry and wet deposition are implemented as first-order processes into a 0-d box model of the photochemical oxidation of α-pinene and other hydrocarbons, enabling the quantification of the fraction of oxidant reactivity and formation potential of secondary organic aerosol that is removed or prevented by deposition. We find that a significant fraction of both reactivity and aerosol formation potential is removed by deposition, with dry deposition generally outcompeting wet deposition. We will discuss the implications of this result for local and regional atmospheric composition.