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LONG-TERM HEAVY METALS DEPOSITION DYNAMICS IN LACUSTRINE ECOSYSTEMS (NW RUSSIA)

Dmitrii Sadokov

Abstract

As part of global monitoring of contaminants delivery to ecosystems via atmospheric transport it is valuable to investigate the accumulation of pollutants in lacustrine sediments, in particular in those remote from cities and industries as potential sources of pollution. Not only conclusions about human impact have been inferred from the proxies, but they also have been used to distinguish it from climatic-driven shifts. Three relict lakes Khotavets, Pogoskoye and Beloye in North-Western Russia have been cored and studied. The lakes are situated in taiga zone of Russia, and distanced 80-150 km from each other, and differently distanced from the large industrial complex of the Cherepovets city (Vologda region) with metallurgical and chemical industries (Khotavets ? 65 km, Pogoskoye ? 85 km, Beloye ? 130 km), while Lake Khotavetsis located in Darwin Biosphere Reserve, under protection of UNESCO. Vertical quantitative down core distribution of some heavy metals (Zn, Ni, Fe, Pb and others) was evaluated in order to reconstruct long-term accumulation dynamics and patterns in lacustrine sediments. A relatively new whole core x-ray fluorescence method has been applied for elemental analysis, which requires additional remarks and recalculations into the concentration units (from intensity, counts per second), but gives broad opportunities to measure elemental composition of sediments non-destructively. Authigenic sedimentation is dominant since the last glacial period up to present time, and correlation in sedimentation rates of organic matter and some metals (Ni, Cu) have been noticed during the whole Holocene period, which is plausibly due to association or complex formation of metal ions with organic compounds. In the upper part of lakes Pogoskoye and Khotavets sediment sequences Pb and Zn concentrations show the highest quantity. Their concentrations increase rapidly (up to 38 ppm and 289 ppm respectively for Lake Khotavets), and less pronounced are the concentrations of Ni (12 ppm), Cr (62 ppm) and Fe oxide (4200 ppm) in Lake Khotavets, though also distinct . Lake Beloye is the most remote from the probable source of contamination, so no distinct patterns of human impact expressed in metals sedimentation can be inferred from its proxies.

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DOI resolver: doi.org/10.5593/sgem2019v/1.4/s02.028

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