The Reaction between CH3O2 and OH Radicals: Product Yields and Atmospheric Implications.

Abstract

The reaction between CH3O2 and OH radicals has been shown to be fast and to play an appreciable role for the removal of CH3O2 radials in remote environments such as the marine boundary layer. Two different experimental techniques have been used here to determine the products of this reaction. The HO2 yield has been obtained from simultaneous time-resolved measurements of the absolute concentration of CH3O2, OH, and HO2 radicals by cw-CRDS. The possible formation of a Criegee intermediate has been measured by broadband cavity enhanced UV absorption. A yield of ϕHO2 = (0.8 ± 0.2) and an upper limit for ϕCriegee = 0.05 has been determined for this reaction, suggesting a minor yield of methanol or stabilized trioxide as a product. The impact of this reaction on the composition of the remote marine boundary layer has been determined by implementing these findings into a box model utilizing the Master Chemical Mechanism v3.2, and constraining the model for conditions found at the Cape Verde Atmospheric Observatory in the remote tropical Atlantic Ocean. Inclusion of the CH3O2+OH reaction into the model results in up to 30% decrease in the CH3O2 radical concentration while the HO2 concentration increased by up to 20%. Production and destruction of O3 are also influenced by these changes, and the model indicates that taking into account the reaction between CH3O2 and OH leads to a 6% decrease of O3.