J. Phys. IV France 107 (2003) 907
Observations of mercury-containing aerosols in the tropopause regionD.M. Murphy1, D.S. Thomson1, 2 and P.J. Sheridan3, 4
1 Aeronomy Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado, U.S.A.
2 Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, U.S.A.
3 Climate Monitoring and Diagnostics Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado, U.S.A.
4 University of Denver, Denver, Colorado, U.S.A.
In situ analyses with a laser ionization mass spectrometer aboard a high altitude aircraft have shown that a large fraction of aerosols in the bottom few km of the stratosphere contain small amounts of mercury . Electron microscopy of particles collected near the tropopause has also detected mercury. The distribution of mercury onto many particles indicates that the mercury is from local condensation of gaseous mercury onto particles rather than transport of mercury-rich aerosols from surface sources. The layer of mercury-containing aerosols was present at both middle latitudes and the tropics in two seasons. There is therefore good reason to believe that the layer is global in extent. There are indications that bromine and/or iodine may be involved in the conversion of mercury from the gas to particle phase in the upper troposphere and lower stratosphere . Although the results are only semi-quantitative, they are consistent with conversion of much of the available mercury into the particulate phase at those altitudes. Such conversion could have a significant effect on the global lifetime of mercury as well as implications for mercury in rainfall.
© EDP Sciences 2003