The role of halogens in the regulation of the oxidative capacity of the Earth’s troposphere in low-polluted environments

The oxidative capacity, usually represented by the concentration of OH radicals in the troposphere, regulates the lifetime of reactive compounds injected into the atmosphere by the biosphere and by anthropogenic activities. Recently, naturally emitted halogenated species (I, Br, Cl) have been showed to play a significant role in the consumption of global tropospheric ozone, a primary precursor of the hydroxyl radical. So far, the state-of-the-art chemistry of iodine, bromine, and chlorine has been implemented in a few global chemistry-transport models (GEOS-CHEM, CAM-Chem, TOMCAT, WRF-Chem). The 3D global chemistry-climate model (LMDz-INCA) has been recently updated to consider the chemistry of halogens. We present here the impact of this chemistry on the global oxidant budgets as well as the lifetime of chemically active species. We discuss how this chemistry affects the self-regulation of radicals in present low-polluted atmospheres as well as pre-industrial and future climate scenarios.