Search

The White Sea being connected with the Arctic Ocean via the Barents Sea has an influence on its water temperature/salinity structures and biological processes and thus has an indirect impact on the Eurasian climate system. In this work, we have managed to find a correspondence between the climate fluctuation in the Holocene and changes in the geochemical and microfossil properties in the sediment core of the White Sea. For the first time, the element speciation in the sediment core covering about 10,000 cal yr BP period was investigated. The cooling periods (the early Holocene and the Subboreal stage) were characterized by a trend of increase in Si, Al, and Ti contents and Ti/Al ratios, which reflect lithogenous contribution, and decrease in geochemically labile forms of trace elements. A significant increase in the content of organic-bound trace elements and biogenic components (Сorg, BSi, and chlorin) was observed during periods of Holocene climatic optimums. The evident relationship between the metal speciation and indicators of the sedimentation paleoenvironment is observed at the stage of the active phase of early diagenesis after the slowing down of the biogeochemical processes. Down-core decrease in the Mn oxyhydroxide content exhibited a weakening of diagenesis processes at the ~130–150 cm depth.

For the first time based on determination of the geochemical occurrence forms of trace metals the main processes that control the accumulation of elements (Al, Mn, Fe, Mo, Cr, Ni, Co, Cu, Pb, Cd, and As) in the recent sediment cores from the White Sea and Barents Sea were quantified. A high-resolution study of the bottom sediment cores allowed us to estimate the short-term variations (periodicity of 10–15 years) in the accumulation of metals to reveal the periods of maximum Fe and Mn contents in the amorphous hydroxides fraction, which serve as effective adsorbents of the trace elements majority, including heavy metals. The Mn/Fe ratio in the amorphous hydroxides phase can be considered as geochemical indicators of early diagenesis.

The White Sea is an inner subarctic marine basin where sedimentation is known to be influenced by mostly terrigenous processes. In the catchment area of the White Sea, a lot of the mining, manufacture, and pulp and paper industry plants are located whose solid and liquid wastes contain heavy metals, including the toxic ones. Through the solid and dissolved river runoff, atmospheric fluxes, and coastal abrasion, heavy metals enter the seawater where they are involved in various biogeochemical processes before to be precipitated on the sea floor. Many studies of marine sedimentation concern total metal concentration; meanwhile, an assessment of contribution of different biogeochemical processes stays incomplete. In this chapter, we try to evaluate the partitioning among the different forms (speciation) of heavy metals that reflect principal processes of their accumulation in the modern bottom sediments of the White Sea. We study both the rock-forming (Al, Fe, Mn) and trace elements (Mo, Cr, Ni, Co, Cu, Pb, Cd, and As) by use of a modified method of selective sequential chemical leaching.