Total depletion of Hg° in the upper troposphere–lower stratosphere

This is the authors' abstract. We don't add key points for this paper.

Our current understanding of atmospheric mercury lacks fundamental details. Gas phase elemental mercury (Hg°) was measured aboard the NASA DC‐8 research aircraft during the Intercontinental Chemical Transport Experiment‐Phase B (INTEX‐B) conducted in spring 2006 over the North Pacific. Our data confirm efficient chemical cycling of Hg° in the tropopause region and show that it is strongly anti‐correlated with O 3 there, yielding a tropospheric‐stratospheric mixing curve of ∼−0.20 ppqv Hg°/ppbv O 3 . In addition, we found frequent total depletion of Hg° in upper tropospheric (8–12 km) air masses impacted by stratospheric influence. When O 3 mixing ratios were >300 ppbv, Hg° was rarely detected. It appears that in the tropopause and stratosphere Hg° is oxidized on the order of days followed by heterogeneous transformation to particulate mercury. These processes constitute an effective chemical sink for Hg° at the top of the troposphere, which may recycle mercury back to the gas phase as stratospheric aerosols are eventually dispersed into the troposphere.