NERI Technical Report No. 533. Fate of mercury in the Arctic (FOMA). Skov, H., Brooks, S., Christensen, J., Wåhlin, P., Heidam, N.Z., Goodsite, M.E., Larsen, M.R.B., Christiansen, K., Hansen, J.B., Daugaard, B. & Lohse, C. 2005. 57 pp.

 

Summary

 

Usually mercury has a lifetime of about 1 year or more in the atmosphere. However, during Arctic spring the lifetime is only a few hours due to fast atmospheric processes that convert gaseous elemental (GEM) to reactive gaseous mercury (RGM) during Atmospheric Mercury Depletion Events (AMDEs). Then RGM is removed quickly from the atmosphere by deposition. It is important to quantify and understand the processes responsible for the removal of mercury from the atmosphere due to the negative environmental impact of mercury .

 

A series of methods is developed for measuring the fractions of atmospheric mercury with higher temporal or spatial resolution than previously. If these new methods are applied together with micro-meteorological methods, they make it possible to measure the flux of Total Atmospheric Mercury (TAM) in the Arctic. This is important in order to get a mass balance for atmospheric mercury and to establish a good understanding of the processes that can be used to make a new chemical parameterisation for the model. The parameterisation can then be used to generalise the results in atmospheric chemical transport models e.g. the Danish Eulerian Hemispheric Model (DEHM).

 

In the present project the first flux measurements ever of RGM have been carried out together with flux measurements of GEM. These measurements show that AMDEs increase the mercury burden in the Arctic. This occurs though the conversion of GEM to RGM followed by fast deposition of RGM to the snow. The results are applied in a new parameterisation of atmospheric mercury in DEHM. North of the Polar Circle about 200 tons/year is deposited when AMDEs are included. A model calculation of mercury deposition without AMDE only gave about 90 tons/year.

 

Experimental results show that the dynamics of atmospheric mercury are far more complicated than described by the present model parameterisation in DEHM. Most probably GEM is oxidised close to the surface or directly on the surface. Sea salt from refrozen leads together with sunlight are responsible for the GEM removal and for the simultaneously removal of ozone. In those processes RGM is formed. Subsequently RGM is quickly removed from the atmosphere by deposition.

 

Full report in pdf format (1,520 kB).