Mercury in particulate matter over Polish zone of the southern Baltic Sea

Important Hg transformations can occur at the air–water interface where polluted terrestrial air masses meet humid, halogen-rich marine air masses over the southern Baltic Sea. These chemical and physical processes include gas-to-particle conversion that led to an increase of Hg associated with coarse particles, which due to higher dry deposition rates, enhanced local scale deposition and limited the transport of this toxic trace metal. Daily (24 h) sampling of size-segregated atmospheric particles revealed the sea to be a sink for Hg during winter months and as a source of Hg during summer months. Poland is one of the major Hg emitters among the Baltic States according to International HELCOM Reports. Thus, important measurements in this region were conducted over a one-year period from December 18, 2007 to December 15, 2008. The range in concentrations of Hg in particulate matter (2–142 pg m−3) at the Polish site are comparable to other measurements at sites along the coastal areas of the Baltic Sea. Annual Hg(p) represents 1% of the total atmospheric Hg (HgTOT) under unpolluted or background ambient conditions. A major source of atmospheric Hg in this area is the combustion of fossil fuels, especially coal burning used for home heating. This was clearly seen in the statistically higher mean concentration of 24 pg m−3 observed during the heating season compared to the 15 pg m−3 measured during the non-heating season. Construction activities e.g., cement manufacturing, gravel extraction, and waste incineration during the warm season strongly influenced Hg concentrations and led to an increase in Hg(p) on working days compared to weekend days.