Mercury labile and stabile fractions in marine sediments from the Spitsbergen region

Mercury (Hg) is one of the most toxic metals found in the natural environment, it is a highly reactive element and remains in the environment biomagnifying in trophic chains. The presence of volatile mercury, which has a tropospheric half-life of several months, makes it persist in the atmosphere long enough to be transported long distances polluting the polar regions. Runoff from melting glaciers and geological weathering of the bedrock also have a significant impact on mercury concentrations in the region. Glacier-fed rivers reach the studied fjords, transporting pollutants from these sources, and the Norwegian Sea is a marginal sea. The purpose of this study was to determine the processes and transformations of mercury fractions in sediment cores from Spitsbergen fjords. Eleven bottom sediment cores collected in Kongsfjorden and Hornsund fjords were studied. The sediment samples were analysed by thermodesorption using a DMA-80 direct mercury analyzer (Milestone). Analysis of the processes in the sediment cores and the percentage of the Hg fraction makes it possible to determine the fate of mercury in the Arctic environment. An important feature of the mercury speciation profiles at all stations studied is the dominance of stable fractions. Both diagenesis processes occurring in the sediments involving the transformation of labile fractions into stable fractions and the direct delivery of these fractions to the bottom sediments are responsible for this. The location of the station, including its distance from the glaciers, as well as its depth, was an important factor determining the concentration and proportion of mercury fractions in bottom sediments in the study area. Understanding the fate of mercury in the Arctic environment helps identify its sources and predict further changes, which are strongly influenced by the changing climate. The conducted study indicates that the process of melting glaciers, as a secondary source of pollutants, increases its importance in supplying them to the marine environment.