Arctic - A sink for atmospheric mercury

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Recently, a new phenomenon has been shown which implies that the deposition flux of mercury in the Arctic is considerable at a time of the year when biota are preparing for peak summertime activity. During spring 2000, frequent episodic depletions in mercury vapour (TGM) concentrations were observed at NILUs research station at Svalbard (Ny-Ålesund).
The depletion of TGM correlates very well with the depletion of ground level ozon. This phenomenon is caused by the specific chemical and physical conditions that occur in the Arctic during the spring where TGM is transferred to more reactive species of mercury, which are more available for biota. Mercury is one of the major pollutants in the Arctic environment. Sources of mercury in the Arctic are poorly known partly due to the lack of information on emission sources in the polar region, and partly due to a lack of understanding of the transport processes of atmospheric mercury from source regions in e.g. Europe and North America (Berg et al., 2001). Measurements have shown that the concentrations of mercury in the Arctic are considerably higher than those reported from Antarctica (De Mora et al. 1993). This is due to anthropogenic emissions. In contrast to other heavy metals, atmospheric mercury is dominated by vapour phase (TGM) mercury, and the particle phase makes up only a small fraction of total airborne concentrations.
Arctic - A sink for atmospheric mercury
During spring 2000, frequent episodic depletions in mercury vapour concentrations were seen at Svalbard. The TGM depletion episodes correlated very well with the depletion of ground level ozon during a three month period (February - May) after polar sunrise. Highly variable concentrations of TGM and ozon were observed with a pronounced tendency towards unusually low concentrations. This phenomenon was first observed at Alert in the Canadian Arctic in 1995 (Schroeder et al 1998). Measurements in Barrow, Alaska (Lindberg et al. 2000) and Ny-Ålesund in 2000 have shown that this is not only a local occurence for Alert. These episodes are caused by the specific chemical and physical conditions which occur in the Arctic during the spring. Earlier investigations have shown that the depletion of ozone is due to the formation of elevated concentrations of oxidising radicals in the atmosphere.
Arctic - A sink for atmospheric mercury

Tekran mercury monitor inside the Zeppelin station. Apparently, atmospheric mercury is similarly affected. In this case, TGM is oxidised and converted to more reactive species, which have a considerably higher deposition velocity than the vapour phase species, which again leads to an overall enhanced deposition flux. The reactive species of mercury are more easily available for biota than TGM. This implies that the deposition flux of mercury in the Arctic is considerable at a time of the year when biota are preparing for peak summertime activity, and may also explain the increased concentrations observed in Arctic biota and sediments (AMAP 1997). The phenomenon described above was not revealed before high resolution measurements of TGM with automatic monitors were introduced in the Arctic. Manual sampling systems have been used both at Alert and Ny-Ålesund earlier without resolving these depletion episodes (Schroeder et al. 1995; Berg et al. 2000). NILU installed a high resoulution, automatic monitor (Tekran Model 2537A) at the new research station at the Zeppelin mountain, Ny-Ålesund, February 2000. The mercury measurements are funded by the Norwegian State Pollution Authority, and will be carried out for at least three years.

Arctic - A sink for atmospheric mercury

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