Известия Томского политехнического университета: Инжиниринг георесурсов (Nov 2020)
FIRST ISOTOPE-HYDROGEOCHEMICAL DATA ON THE NATURAL WATERS OF THE SOUTH-EAST SLOPE OF THE CHEKANOVSKY RIDGE (ARCTIC AREAS OF THE SIBERIAN PLATFORM)
Abstract
The relevance of the study is caused by the obtaining of the previously unexplored isotope-hydrogeochemical data on the natural waters of the south-east slope of the Chekanovsky ridge (Arctic regions of the Siberian Platform). The study area is difficult due to the access continuous distribution of permafrost. The aim of the research is to identify the geochemical features of the natural waters of the south-east slope of the Chekanovsky ridge. Methods. Field sampling was carried out in accordance with generally accepted methods. Chemical analytical studies were performed by titrimetry, ion chromatography and inductively coupled plasma mass spectrometry. The analysis of the isotope ratios (δD, δ18O, and δ13СDIC) was carried out on an Isotope Ratio Mass Spectrometer FinniganTM MAT 253 equipped with H/Device (for analyzing δD ratios) and GasBench II (for analyzing δ18O and δ13СDIC ratios) sample preparation attachments. In the study of hydrogeochemical data, we used geochemical coefficients (Ca/Na, Ca/Mg, Ca/Si, Mg/Si, Na/Si, Si/Na, rNa/rCl and SO4/Cl), coefficients of concentration and water migration according to A.I. Perelman. Results. The paper presents the first results of isotope-geochemical studies of the natural waters of the south-east slope of the Chekanovsky ridge, located in the downstream of the Lena river, in the Arctic regions of the Siberian Platform. The rivers and temporary streams formed during the period of thawing of permafrost have been studied. It was established that the waters are ultra-fresh with a total salinity of 63 to 100 mg/dm3, neutral and slightly alkaline in terms of pH (6,9–7,9), characterized by chemical oxygen demand (COD) from 1,6 to 9,7 mgO/dm3. River waters have a predominantly bicarbonate calcium composition. Temporary streams are characterized by the predominance of sulfate ion, as well as low COD values – from 1,6 to 3,1 mgO/dm3. The calculated coefficients of water migration were distributed as follows: very high intensity of migration of I, Se, Br; high Sr, B, Sb; average As, P, Ni, Cu, Li, Ba, Zn, U, Sn, Mo; low Sc, Y, Be, Mn, Pb, Si, Ge, Cr, Rb, Co, V, Fe, Ga, Th, Al, Zr, Ti. The isotopic ratios of oxygen and hydrogen were studied in a wide range for δ18O – from –24,2 to –19,5 ‰, and for δD – from –183,0 to –149,3 ‰. According to the isotopic composition the waters has a meteor origin. A shift in the water supply from winter to summer is observed for rivers, while winter (snow) sources are more pronounced for temporary streams. The δ13CDIC isotopic ratios range from –9,7 to –7,2 ‰. In river waters, both positive (up to –7,2 ‰) and negative (up to –9,7 ‰) deviations of δ13CDIC relative to samples taken from temporary streams (characterized by values from –8,0 to –7 ‰), are observed. It supposed enrichment of water with carbon dioxide and heavy isotope 13C firstly due to material and isotopic exchange with the carbonate rocks weathered by soil CO2 formed from plants of type C4.
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