Suchergebnisse

Reactive iodine plays a key role in determining the oxidation capacity, or cleansing capacity, of the atmosphere in addition to being implicated in the formation of new particles in the marine boundary layer. The postulation that heterogeneous cycling of reactive iodine on aerosols may significantly influence the lifetime of ozone in the troposphere not only remains poorly understood but also heretofore has never been observed or quantified in the field. Here, we report direct ambient observations of hypoiodous acid (HOI) and heterogeneous recycling of interhalogen product species (i.e., iodine monochloride [ICl] and iodine monobromide [IBr]) in a midlatitude coastal environment. Significant levels of ICl and IBr with mean daily maxima of 4.3 and 3.0 parts per trillion by volume (1-min average), respectively, have been observed throughout the campaign. We show that the heterogeneous reaction of HOI on marine aerosol and subsequent production of iodine interhalogens are much faster than previously thought. These results indicate that the fast formation of iodine interhalogens, together with their rapid photolysis, results in more efficient recycling of atomic iodine than currently considered in models. Photolysis of the observed ICl and IBr leads to a 32% increase in the daytime average of atomic iodine production rate, thereby enhancing the average daytime iodine-catalyzed ozone loss rate by 10 to 20%. Our findings provide direct field evidence that the autocatalytic mechanism of iodine release from marine aerosol is important in the atmosphere and can have significant impacts on atmospheric oxidation capacity. ; We acknowledge financial support from the Academy of Finland (3282290, 306853, 296628, 310626, 315203, 311932, 299574, 326437, 307537, 316114, and 326948), Jane and Aatos Erkko Foundation, European Research Council Executive Agency under the European Union's Horizon 2020 Research and Innovation Programme (Project ERC-2016-COG 726349 CLIMAHAL), European Research Council (GASPARCON, grant 714621), European Research Council via Atmospheric Gas-to-Particle conversion (ATM-GTP) 266 (grant 742206), H2020 European Research Council (grant CHAPAs [850614]), and the Aerosol, Clouds and Trace Gases Research Infrastructure 2—Trans-National Access Consistent Consistent and Mobile Direct Observation of Cluster Formation in Diverse European Environmental Zones: Mace Head (ACTRIS-2 TNA CONDENZ:MHD) from the European Union's Horizon 2020 Research and Innovation Programme under grant agreement No. 654109. We would also like to acknowledge the Mace Head operational support from the EPA-Ireland, Department of Communications, Climate Action and Environment and contributions from COST Action CA16109 (COLOSSAL), MaREI, and the SFI Research Centre for Energy, Climate and Marine.