A gas-to-particle conversion mechanism helps to explain atmospheric particle formation through clustering of iodine oxides
Juan Carlos Gómez Martı́n, Thomas R. Lewis, Mark A. Blitz, J. M. C. Plane, Manoj Kumar, Joseph S. Francisco, Alfonso Saiz‐Lopez
Abstract
Abstract Emitted from the oceans, iodine-bearing molecules are ubiquitous in the atmosphere and a source of new atmospheric aerosol particles of potentially global significance. However, its inclusion in atmospheric models is hindered by a lack of understanding of the first steps of the photochemical gas-to-particle conversion mechanism. Our laboratory results show that under a high humidity and low HO x regime, the recently proposed nucleating molecule (iodic acid, HOIO 2 ) does not form rapidly enough, and gas-to-particle conversion proceeds by clustering of iodine oxides (I x O y ), albeit at slower rates than under dryer conditions. Moreover, we show experimentally that gas-phase HOIO 2 is not necessary for the formation of HOIO 2 -containing particles. These insights help to explain new particle formation in the relatively dry polar regions and, more generally, provide for the first time a thermochemically feasible molecular mechanism from ocean iodine emissions to atmospheric particles that is currently missing in model calculations of aerosol radiative forcing.