Importance of halogenated chemistry and its influence on the total ozone budget

Despite of their importance, halogen atom sources in the marine boundary layer is still an open question which requires further attention.

This chemistry is now recognized to be very important both in coastal areas and in the Polar Regions. Under conditions where NO₂ is present, chlorine atoms form ozone, increasing the amount in the atmosphere. In addition, ozone reacts with organics to form particles that are known to have negative health effects. The impact of particles on climate change, through their direct effect on light scattering and indirect effect on clouds, is in part responsible of the great uncertainty to predict climate change and sea salt particles have been shown to play a key role.

In short, there is now overwhelming evidence that halogen atom plays a key role in tropospheric chemistry. Despite this, the tropospheric concentrations of those photochemical active halogen gases that have been measure in air (Cl₂, ClNO₂, Br₂ and BrCl) are under-predicted by at least an order of magnitude by models of the marine boundary layer. It is clear that the disconnect between measurements and models must be due to a lack of understanding of the kinetics and mechanisms of reactions of sea salt particles that lead to the generation of gas phase halogens. At least part of this is due to new frontiers in the interaction of gases with condensed phases that were not previously recognized.