Mercury geochemistry of deep-sea sediment cores from the Kuril area, northwest Pacific

Abstract

In the present study we report mercury data in the sediment cores obtained during a Germany-Russian and Russian-Germany cruises onboard the Vessels Sonne and Akademik M.A. Lavrentyev in Kuril area. This region cover an extensive area of the Northwest Pacific included the trench system and adjacent abyssal plain, ranging zone off the Kuril Islands. Kuril area is characterized by high water biological productivity, intensive volcanic activity, and hydrological features. Mercury concentrations in sediment cores were analyzed using a Zeeman atomic absorption spectrometer with high frequency modulation of light polarization and a pyrolysis attachment to determine its occurrence, distribution, and deposition flux. Mercury concentrations in the sediments ranged between 8 and 170 ppb; its minimal concentrations (8–15 ppb) were detected in sandy turbidites. For the pre-industrial period, Hg flux ranged between 33 and 36 µg/m2 year. The maximum Hg flux (44 µg/m2 year) corresponded to the 1980, with decreases of up to 30 µg/m2 year in modern sediments (top-core sediment samples). The Hg outlet temperature in the bottom sediments corresponded to a physically sorbed form of Hg and depends on the Hg content of diatoms (siliceous residues). Hg concentrations were significantly positivly correlated with total organic carbon content but negativly correlated with Al, Fe, Zr, and Sr contents. Thus, two main factors affected Hg burial in bottom sediments; atmospheric deposition of Hg and biological productivity. The effect volcanic activity has not been clearly established in this study.