Reaktionen des Quecksilbers und seiner Spezies in bodennahen Luftschichten der Antarktis

Long-range atmospheric transport of mercury, its transformation to more toxic methylmercury compounds, and their bioaccumulation in the aquatic food chain have motivated international research on mercury as a pollutant of global concern. The background concentration of gaseous elemental mercury (Hg"0) in the lower troposphere of the northern hemisphere is generally around 1,9 ng/m"3 and 1,3 ng/m"3 in the southern hemisphere respectively. Highly time-resolved atmospheric mercury measurements in the Antarctic have shown that mercury depletion events do also occur in the Antarctic at Neumayer Station during the first three months after polar sunrise. This phenomenon leads to an increased input of atmospheric mercury into the polar ecosystem. A possible explanation for mercury depletion events may involve chemical or photochemical oxidation of Hg"0 to Hg"2"+ [resulting either in particle-associated mercury (Total Particulate-Phase Mercury: TPM) and/or reactive gaseous mercury (RGM) species] and significantly enhanced deposition fluxes of mercury leading to unequivocally increased input of atmospheric mercury into the polar ecosystem. The Antarctic mercury depletion phenomenon is strongly correlated with ground-level ozone depletion episodes. These trophospheric ozone loss events in the Antarctic are associated with enhanced bromine monoxide concentrations in the free troposphere. It is hypothesized that Br atoms and/or BrO radicals are involved in a chemical reaction which destroys ozone. The following depletion of atmospheric boundary layer mercury (at times up to an altitude of #approx# 1 km) is due to a reaction between gaseous elemental mercury and BrO free radicals. In addition methods for the determination of GEM, TPM, and RGM were applied at Neumayer Station during antarctic summer and on board of the German research vessel ''Polarstern''. These Hg-species play a key role in the deposition mechanism of atmospheric mercury and levels of more than 300 pg Hg(II) per cubic meter of air, associated with simultaneously decreasing levels of gaseous elemental mercury were found. (orig.)SIGLEAvailable from TIB Hannover: RA 3251(03/19) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman