The Reaction Between CHO and OH Radicals: Product Yields and Atmospheric Implications

The reaction between CHO and OH radicals has been shown to be fast and to play an appreciable role for the removal of CHO 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 HO yield has been obtained from simultaneous time-resolved measurements of the absolute concentration of CHO, OH, and HO radicals by cw-CRDS. The possible formation of a Criegee intermediate has been measured by broadband cavity enhanced UV absorption. A yield of ϕ = (0.8 ± 0.2) and an upper limit for ϕ = 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 CHO+OH reaction into the model results in up to 30% decrease in the CHO radical concentration while the HO concentration increased by up to 20%. Production and destruction of O are also influenced by these changes, and the model indicates that taking into account the reaction between CHO and OH leads to a 6% decrease of O.