Year: 2026
Type: article
Abstract: . Tropospheric reactive iodine influences the oxidizing capacity of the atmosphere and serves as an important source of ultra-fine particles. However, the paucity of observations of gas-phase and aerosol iodine, combined with incomplete understanding and representation of iodine chemistry in models, leads to substantial uncertainties in understanding iodine abundance, speciation, and impacts. Motivated by known gaps in previous modeling studies, we introduced speciated aerosol iodine and aerosol iodide recycling to the global chemical transport model, GEOS-Chem. Modeled aerosol iodine is speciated into fine and coarse mode soluble organic iodine (SOI), iodate, and iodide. Aerosol iodide is recycled into the gas phase via heterogeneous chemistry involving halogen nitrates and hypohalous acids to form I2, ICl, and IBr, which represents an additional source of gas-phase iodine to the atmosphere. Iodide dehalogenation doubles the tropospheric burden of reactive iodine (Iy) while reducing model-measurement bias for IO and aerosol iodine. The rate of aerosol iodine conversion to Iy is more than twice as fast as the combined rates of inorganic ocean emissions and the photolysis of organic iodine gases, suggesting that aerosols are important in mediating the abundance and lifetime of tropospheric Iy. The incorporation of SOI and iodate into the model prevents iodide dehalogenation by partitioning iodide into less reactive reservoirs, which has a stabilizing effect for reactive iodine chemistry. These findings have implications for reactive halogen abundances and global oxidant budgets in the troposphere.
Authors: Allison R. Moon, Leyang Liu, Xuan Wang, Yuk-Chun Chan, Alyson Fritzmann, Ryan Pound, Amy Lees, Lewis Marden, Mat Evans, Lucy J. Carpenter, Jochen Stutz, Joel A. Thornton, Gordon Novak, Andrew Rollins, Gregory P. Schill, Xu-Cheng He, Henning Finkenzeller, Mago Reza, Rainer Volkamer, Kelvin H. Bates, Alfonso Saiz-Lopez, Anoop S. Mahajan, Becky Alexander
Institutions: University of Washington, City University of Hong Kong, University of Hong Kong, University of California, Los Angeles, University of York, NOAA Chemical Sciences Laboratory, University of Helsinki, Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Consejo Superior de Investigaciones Científicas, Instituto de Química Física Blas Cabrera
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,725
Awards: G1061138800, G1515677456, Collaborative Research: NSFGEO-NERC--Coupled Tropospheric Reactive Halogen Chemistry in the Subtropical Marine Boundary Layer, The role of iodine oxoacid particle formation on a global scale, Ozone dry deposition to the sea surface microlayer, G235046013, G434337789, Formation of marine low-level cloud seeds and the global impact - MARCLOUD, The role of iodine oxoacid particle formation on a global scale, Collaborative Research: TI3GER--Technological Innovation Into Iodine and Gv-aircraft Environmental Research, Collaborative Research: NSFGEO-NERC--Coupled Tropospheric Reactive Halogen Chemistry in the Subtropical Marine Boundary Layer, PANORAMA - A Yorkshire partnership for training in environmental careers, NSFGEO-NERC:BLEACH
OpenAlex ID: W7128990804