Spatial and temporal variability of iodine in aerosol

Type Article
Acceptance Date 2020 IN PRESS
Language English
Author(s) Gómez Martín Juan Carlos1, Saiz-Lopez Alfonso2, Cuevas Carlos A2, Fernandez Rafael P3, Gilfedder Benjamin4, Weller Rolf5, Baker Alex R6, Droste Elise6, 7, Lai Senchao8
Affiliation(s) 1 : Instituto de Astrofísica de Andalucía, CSIC, 18008, Granada, Spain
2 : Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain
3 : Institute for Interdisciplinary Science, National Research Council (ICB-CONICET), FCEN-UNCuyo, Mendoza, 5501, Argentina
4 : Limnological Research Station, University of Bayreuth, Germany
5 : Alfred-Wegener-Institut Helmholtz Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany
6 : Centre for Ocean and Atmospheric Science, School of Environmental Sciences, University of East Anglia, Norwich, UK
7 : Department of Environmental Sciences, Wageningen University and Research Centre, Wageningen, Netherlands
8 : South China University of Technology, School of Environment and Energy, Higher Education Mega Center, Guangzhou 510006, P.R. China
Source Earth and Space Science Open Archive In Press
DOI 10.1002/essoar.10505416.1
Abstract

In this work we describe the compilation and homogenization of an extensive dataset of aerosol iodine field observations in the period between 1963 and 2018 and we discuss the spatial and temporal dependences of total iodine in bulk aerosol by comparing the observations with CAM-Chem model simulations. Total iodine in aerosol shows a distinct latitudinal dependence, with an enhancement towards the northern hemisphere (NH) tropics and lower values towards the poles. This behavior, which has been predicted by atmospheric models to depend on the global distribution of the main oceanic iodine source (which in turn depends on the reaction of surface ozone with aqueous iodide on the sea water-air interface, generating gas-phase I<sub>2</sub> and HOI), is confirmed here by field observations for the first time. Longitudinally, there is some indication of a wave-one profile in the Tropics, which peaks in the Atlantic and shows a minimum in the Pacific, following the wave-one longitudinal variation of tropical tropospheric ozone. New data from Antarctica show that the south polar seasonal variation of iodine in aerosol mirrors that observed previously in the Arctic, with two equinoctial maxima and the dominant maximum occurring in spring. While no clear seasonal variability is observed in NH middle latitudes, there is an indication of different seasonal cycles in the NH tropical Atlantic and Pacific. A weak positive long-term trend is observed in the tropical annual averages, which is consistent with an enhancement of the anthropogenic ozone-driven global oceanic source of iodine over the last 50 years.

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