Fractionation of mercury in aerosols of the southern Baltic coastal zone

The form in which Hg occurs in the atmosphere is important to understand the toxicity and bioavailability of this metal. So far, research on mercury speciation in the atmosphere has mostly focused on its three forms: elemental gaseous mercury (GEM/Hg0), reactive gaseous mercury (GOM/Hg2+) and mercury bound in aerosols (TPM). However, these studies do not provide complete information on mercury compounds in aerosols. Only a few publications on mercury fractionation in TPM have been published, but these have focused mainly on describing the method and have provided only a limited number of environmental results. Therefore, the research aimed to identify forms of mercury occurring in aerosols in the coastal zone of the southern Baltic Sea, as well as to determine factors affecting the temporal changes in the share of individual Hg fractions. Aerosol samples were collected in Gdynia (Poland) from May 2016 to January 2017. A thermo-desorption technique was used for the determination of total mercury and Hg fractions. Mercury in aerosols was present mainly in labile factions related to mercury halides, mercury nitrate and organic mercury as well as gaseous mercury. The stable Hg fraction, mainly bound to Hg sulphide, constituted only 7% of total particulate mercury. The conducted research also allowed to determine the origin of mercury sources in aerosols. In the winter it was burning of fossil fuels, and in the summer biological activity and emission from the sea. [Display omitted] •The main mercury fraction in aerosols was related to halides and organic compounds.•The important fraction was also gaseous mercury adsorbed on aerosols.•Land sources mainly emitted gaseous mercury and mercury sulfide adsorbed on aerosols.•Marine air masses were connected with mercury halides and organic compounds.