Известия Томского политехнического университета: Инжиниринг георесурсов (Apr 2021)
HYDROGEOLOGY AND HYDROGEOCHEMISTRY OF THE «KAMENSKOE» FIELD OF RADON-RICH WATERS (NOVOSIBIRSK)
Abstract
The relevance of the research is to obtain new information on hydrogeology and hydrogeochemistry of underexplored fields Novosibirsk radon waters in the south of Western Siberia. Novosibirsk is one of those few cities in Russia that were laid on granites – a source of radon emanation (222Rn). The study area is confined to the inner area of the large Novosibirsk granitoid massif. There were no scientific generalizations of the available factual material. The aim of the research is to identify the features of the hydrogeological structure and hydrogeochemistry of the mineral hydro-radon occurrence «Kamenskoe» and to study the forms of migration of chemical elements and the saturation degree to minerals. Methods. Sampling was carried out in accordance with generally accepted methods. Compilation and analysis of hydrogeochemical data was carried out using the software Microsoft Excel, STATISTICA, SURFER, Grid Master. In the environment of Visual Minteq and WATEQ4f software packages, physicochemical calculations of the migration forms of chemical elements in radon waters and the degree of their saturation to a number of rock-forming minerals were performed. Results. In the hydrogeological section of the «Kamenskoe» hydro-radon occurrence two aquifers was established (from top to bottom): pore water of Quaternary aquifer and fissure-vein waters of Upper Paleozoic granites. In the central part of Novosibirsk, the infiltration of atmospheric precipitation is complicated, the natural regime of groundwater supply is disturbed. Pore-stratal waters of Quaternary sediments, waters of the zone of regional fracturing and fracture-vein waters of Upper Paleozoic granites are located in a common mixing area, which is influenced by flooding and anthropogenic pollution. Thus, in the water-bearing complex of the Upper Paleozoic granites, two hydrogeochemical zones are distinguished: the upper one is the waters of the regional fracturing zone in the flooding area under anthropogenic impact, and the lower one is the fractured-vein mineral radon waters. Mineral radon fissure-vein waters of granites are not subject to anthropogenic influence and are installed in well no. 4p (interval 73–74 m) and in well no. 16 at depths from 73 to 128 m. They are cold, fresh, HCO3 Na-Ca and HCO3 Na-Mg-Ca composition with TDS from 613,4 to 689,9 mg/dm3 and silicon content 10,3–13,6 mg/dm3. They are characterized by pH from neutral to slightly alkaline (6,9–7,8) and oxygen-nitrogen composition of water-dissolved gases. The established activity of 222Rn varies in the range of 1101–1570 Bq/dm3 (strongly radon waters according to the classification of N.I. Tolstikhin); content: 238U from 5,6∙10–3 to 6,5∙10–3 mg/dm3 and 226Ra from 2,7∙10–9 to 1,8∙10–8 mg/dm3. With an increase in the total mineralization of radon waters, the proportion of simple cationic forms of Mg2+, Ca2+, Na+, Sr2+, Ba2+ in solution decreases, which is associated with the formation of hardly soluble carbonate and sulfate compounds. In radon waters, Fe(II) forms are presented as Fe2+, FeHCO3+, FeCO30. Ferrum (III) migrates in the form of positively charged hydroxo complexes Fe(OH)2+ and neutral Fe(OH)30. Among the forms of manganese migration, the simple cation Mn2+ (43,71–99,99 %) dominates, the remaining forms are represented by MnHCO3+ (9,89–28,27 %) and MnCO30 (0,01–37,39), to an even lesser extent MnSO40 (0,20–2,25 %), MnCl+ (0,04–1,12 %) and MnOH+ (0,01–0,05 %). The chemical forms of migration of heavy metals (nickel and copper) are presented in the form of free cations (Ni2+, Cu2+), hydrocarbonate (NiHCO3–, CuHCO3–) and carbonate (NiCO30, CuCO30) complexes. Copper also migrates in the neutral form Cu(OH)20. Beryllium (hazard class 1) migrates in the form of the hydroxo complex Be(OH)2. The established features of the geochemical types of waters, the proportional distribution of forms and coefficients of water migration of chemical elements revealed the complication of the composition of equilibrium minerals from siderite, ferrihydrite, and greenalite in surface waters to saturation with calcite, dolomite, magnesite, rhodochrosite, and talc in fractured vein waters of the Upper Paleozoic granites. The forms of migration of chemical elements determine the mechanisms of dissolution/precipitation of mineral compounds.
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