Depletion of atmospheric mercury
The THALOZ project investigated the role of reactive halogens in troposphere oxidation chemistry, their impact on ozone, and consequent effect on radiative forcing of climate. This multidisciplinary concerted effort combined satellite observations, laboratory studies, model development and application. Thereby, data gathered have been applied to new models to predict atmospheric composition changes and radiative forcing of climate. More specifically, specific atmospheric composition changes in toxic species including ozone and mercury were extensively studied. Normally, mercury in ambient air is found in its elemental form and distributed globally. Despite this, the novel high-resolution mercury data for the Antarctic showed that mercury depletion events occur in the Antarctic after polar sunrise. According to the project study, BrO radicals and ozone considerably affect the boundary layer chemistry of springtime mercury depletion events in the Antarctic. Thereby, the oxidation of elemental mercury, followed by adsorption and deposition of the oxidised form may be the cause of mercury depletion. This complements a recent Canadian research work about significant depletion of total gaseous mercury in the Canadian Arctic during the months after polar sunrise. A considerable input of atmospheric mercury to polar ecosystems is anticipated during the short springtime period, when biological activity reaches is full potential. This major feature of the global cycle of mercury can have serious environmental and public health implications.
