STABLE ISOTOPES AS A TOOL TO CHECK THE BOUNDARIES OF CLOSED ECOSYSTEMS, BY THE EXAMPLE OF THE VITIM RIVER BASIN

Abstract

The relevance of investigation consists in revealing the influence of the environment macroscale factors on the variation of chemical and isotopic composition of large water reservoirs. The aim of the research is to study the influence of relatively closed ecosystem changing on chemical and isotope composition (δD, δ18O и δ13СDIC) of river waters on the example of Vitim river. Methods. Analysis of the chemical composition of waters was carried out using titration at the Basic Research Laboratory of Hydrogeochemistry at the School of Earth Sciences and Engineering of the Tomsk Polytechnic University. The δD, δ18O, δ13СDIC values of waters and dissolved inorganic carbon were determined in the Research Equipment Sharing Center at the Institute of Geology and Mineralogy SB RAS using the Isotope Ratio Mass Spectrometer FinniganTM MAT 253, equipped with the H/Device and GasBench II. Results. The paper introduces the data of the complex analysis of the hydrogen, oxygen and carbon isotope composition (δD, δ18O and δ13СDIC) in waters and DIC of the largest East Siberia river Vitim and some of its inflows. The δD and δ18O values indicating the meteoric origin of waters vary from –173,0 to –149,1 ‰ for hydrogen and from –23,3 to –20,2 ‰ for oxygen. Local Meteoric Water Line of the region under investigation was plotted. DIC concentration in waters depends on the type of landscape and its changing. The δ13СDIC values vary from –17,1 to –9,0 ‰ and show that main sources of DIC were soil diffusion and biogenic CO2. It was shown that isotope characteristic in association with the concentration characteristic of DIC in waters is an instrument very sensitive to landscape change (conventional board of the closed ecosystems).

Keywords

• vitim river
• surface waters
• stable oxygen
• hydrogen and carbon isotopes
• associated isotope and concentration characteristic of waters