Accumulation of Organic Matter, Heavy Metals, and Rare-Earth Elements in Marine Sediment at Different Distance from the
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mulation of Organic Matter, Heavy Metals, and Rare-Earth Elements in Marine Sediment at Different Distance from the Indigirka River Delta V. S. Sevastyanova, *, O. V. Kuznetsovaa, V. S. Fedulova, V. Yu. Fedulovaa, N. V. Dushenkoa, S. G. Naimushina, Ya. V. Bychkovab, †, and A. P. Krivenkoa aVernadsky
Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, ul. Kosygina 19, Moscow, 119991 Russia b Lomonosov Moscow State University, Faculty of Geology, Moscow, 119234 Russia *e-mail: [email protected] Received June 20, 2020; revised July 7, 2020; accepted July 7, 2020
Abstract—Studies have shown that the concentration of heavy carbon isotope in the organic matter (OM) in the surface layer of the marine sediment increases and the amount of terrigenous OM decreases by about 1.4 times with increasing distance from the Indigirka River delta from 50 km to 600 km. This is accompanied by 1.3–2.1 times decrease of heavy metals and 1.3–1.4 times decrease of rare-earth elements (REE). A strong correlation is observed between the contents of OM, heavy metals, and REE in marine sediments, with the exception of the Cd and W contents. At a distance of 50 km from the river delta, the heavy metals contents exceed their Earth’s crust clarke values, while REE contents are higher than those of the North American Shale Composite (NASC). The opposite pattern is observed at a distance of 600 km from the river delta. Keywords: carbon isotopic composition, East Siberian Sea, Indigirka, marine sediments, organic matter, heavy metals, rare earth elements, ICP-MS, microwave digestion DOI: 10.1134/S0016702920120046
INTRODUCTION At present, the East Arctic area has been the focus of numerous studies in light of ecological, geopolitical, economic, and other factors. Of great interest is the study of sedimentation and transformation of OM in the Arctic zone in relation with climatic change, anthropogenic impact, and formation of mineral resources. The sedimentation in the East Siberian Sea is peculiar in a shallow depth, volume of river runoff, and distribution of riverine waters (Vetrov et al., 2008; Flint et al., 2018). The surface of the East Siberian Sea during the most part of the year is covered by ice, and only 35% of its area remain open even by the end of summer. Most part of the Chukchi and East Siberian shelves is covered by reduced gray, dark gray, or black sediments. The bottom sediments are fine-grained regardless of distance from the East Siberian Sea coast (Astakhov et al., 2013; Ivanov et al., 2012). An increase of temperature in the Arctic region leads to the permafrost melting, an increase of river runoff, a decrease of ice sheet, and an increase of the number of storms. The permafrost degradation causes the release of soluble metal salts and OM from soil and † Deceased.
their supply with river runoff into the sea. An increase of the degradation rate of coastal and underwater permafrost on the East Siberian shelf leads to the involvement of a great amount of organic matter in the present-day biogeochemical c
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