Factors influencing variability of mercury input to the southern Baltic Sea

- More frequent precipitation led to increased atmospheric and terrestrial Hg.
- Atmospheric and terrestrial Hg tend to drop in warmer heating season.
- Regional domestic coal burning determines Hg input to the Baltic.
- Maritime air masses from remote sources enhance Hg in the coastal zone.

The southern Baltic countries have been identified as significant sources of Hg into the sea. Are anthropogenic activities the sole source? How do meteorological parameters influence the deposition? Studies on input of Hg to the Baltic were conducted in 2008-2012 in the Polish coastal stations. The riverine load was found to depend directly or indirectly on the amount of precipitation and catchment type. Input of atmospheric Hg increased along with the number of precipitation episodes from remote maritime air masses, as well as with the number of days when continental air masses from regional (when domestic heating prevailed) and remote sources moved over the Baltic, during the heating season. During the non-heating season metal input was found to be proportional to episodes of rain from continental regional air masses and to the number of days under influence of continental and maritime air masses from regional sources.