The largest CO2-rich mineral water resource in the Sikhote-Alin ridge of Eastern Russia at Gornovodnoe village was studied. The high-pCO2 groundwaters are cold (5.8–10 °C) with pH 5.9–6.5, TDS varied from 1.2 to 2.7 g/l and belong to Ca–Mg (Ca–Na)–HCO3 type. New data on geology, mineralogy, hydrogeology and hydrogeochemistry, in conjunction with isotope data of water and gas phases, have provided a much better understanding of the origin of this distinctive groundwater. It was found that this water is of meteoric origin, but its unusual chemical composition is controlled by interactions of CO2-rich groundwater and the aquifer materials. The dissolved CO2 gas makes the water slightly acidic (at about pH 6.2) which increased the leaching of many trace elements from host volcanic rocks typically considered immobile at these pH values. 3He/4He ratios and δ13C indicate that mantle degassing is important as a source of deep exogenic fluids. The cold CO2-rich groundwater of the Eastern Sikhote-Alin ridge is the result of interactions between fresh groundwater of meteoric origin, mantle gases and the host volcanic rocks. It thus highlights connectivity between deep and shallow fluids along with deep fractures related to ancient terrane boundaries.

New data on geochemistry of the Paratunka deposit of mineral waters—Russian biggest geothermal system is presented in this paper. Studied waters are thermal (T = 45–80 °C), alkaline (ph = 7.9–8.7), belong to Ca–Na Cl–SO4 type with reducing environment (Eh = − 150 to − 180 mV) leading to Ce- (+ 0.31) and Eu- (+ 0.8) anomalies. Evolution of chemical type of thermal water from Na–SO4 to Ca–Cl is discussed from the point of water–rock interaction and marine water intrusion as well. REY concentrations are extremely low due to alkaline pH (∑REY = 25–165 ppt). First reliable data on REY concentration in alkaline thermal water, surrounding river water and suspended matter of these waters gave an opportunity to discuss cerium, europium and yttrium anomalies in terms of sorption/desorption processes and pH/Eh dependencies, confirmed by thermodynamic calculations of the REE migration forms.

The behaviour of major ions and rare earth elements (REE) was studied in the hot springs of the volcano Mutnovsky (Kamchatka). We found that the concentration of REE depended on the geochemical type of water, with maximum content of REE being in Ca-SO4 waters. Overall, this study shows that the pH has a significant impact on the content and fractionation of REE.

A 10-year monitoring period of rare earth element and yttrium (REY) contents and REY pattern shapes was carried in four different types of groundwater (fresh, rich-CO2, low thermal and brackish) from Sikhote Alin ridge. Obtained data reveals that REY concentrations and behavior strongly vary in different chemical groundwater types and depend on many factors, including the pH–Eh parameters, TDS and the composition of the bedrocks. Speciation calculations of REY were carried out using the computer program SELECTOR-Windows with the SPRONGS88 database of thermodynamic parameters.

Baransky is an active volcano, located in southern Kurile arc, on the subduction zone between Okhot and Pacific plates. Being active during the last 50 years, it is still a threat to locals and air transport. Geochemical study of hydrothermal system of Baransky volcano gives us an opportunity to understand processes occurring in volcanic structure. Thermal springs of the Kipyaschiy creek basin were studied for major ions, micro and rare-earth elements. Hydrothermal springs are characterized with T = 90–100°C, pH = 1.2 –1.9, Cl = 1.8g/l and SO4 = 4g/l. These conditions have a strong influence on water of Kipyaschiy creek. During fluids/surface water interaction we see fractionation of rare-earth element as indicators of changing physico-chemical parameters of the creek. Solfatars are enriched in trivalent Gd and Lu, bivalent Eu, Tm and Yb and depletion in tetravalent Ce, Tb, Dy and trivalent Ho and Er. Hydrothermal fluids are enriched in all REEs with trend to HREE accumulation, but minimum changes in Ce and Gd.

The authors of the paper have established the geochemical features of the composition of underground waters and regularities of their formation in the areas of the liquidated coal mines of Russia and Ukraine. It is shown that the mine flood resulted in the formation of technogenic waters which geochemical specificity originates in the feeding field and is transformed in the direction of the filtration flow. It depends on the geological structure of sedimentary basins and the presence in the coal and supra-coal beds of the marine, salt-bearing and freshwater groups of geological formations. The water types are distinguished characterizing the conditions and processes of their formation that may be the regional markers in the hydrochemical and geological constructions. The technogenic waters influenced the safety of the underground waters, sources of water supply of the regions, and surface water channels. The pollutions are of local character in space.

This article discusses the joint work of Professor W.M. Edmunds (UK) with his Russian colleagues. He had an important role in the development of hydrogeochemistry in Russia. He was an initiator of the joint research projects with Russian scientists and was actively supporting the idea of holding international conferences on the territory of Russia. In addition, as a follower of V.I. Vernadsky, he was actively promoting Vernadsky's ideas outside of Russia.

This paper presents original data on the content and distribution of major and rare-earth elements in the modern hydrothermal systems of the Paratunka and Bol’shebannyi thermal water deposits. In spite of the similar geochemical type of the waters, the individual sites of the hydrothermal systems differ in the major component composition, which is caused by the time of water–rock interaction, temperature control, and the possible influence of seawater intrusions. The REE concentrations in the studied thermal waters are extremely low (a few tenths of ppb). A distinctive feature of these thermal waters is the presence of a positive Eu anomaly. The possible reasons for its appearance are discussed. Calculation of REE speciation shows that the main parameters controlling the formation of the REE complexes in the Paratunka and Bol’shebannyi hydrothermal systems are their individual chemical properties, as well as pH, Eh, and temperature of the aqueous solution.

Studied waters belong to warm (T=30–50°C), alkaline (pH=8.9–9.3), low mineralized (TDS<235 mg/l) Na–HCO 3 or Na–SO 4 –HCO 3 thermal waters with high content of SiO 2 (up to 81 mg/l) and F (up to 3.9 mg/l), occur on modern volcano–tectonic rejuvenated areas of Eastern Sikhote–Alin orogenic belt. Low 3 He concentration as well as N 2 /O 2 and N 2 /Ar ratios exclude influence of deep mantle fluid. New rare earth element data constrain our understanding of water–rock interaction occurring in the water source region. Meteoric origin of waters is proved by stable isotope values varying from −71‰ to −136.1‰ and from −10.8‰ to −18.8‰ for δ 2 H and δ 18 O respectively. REE patterns reflect high pH, resultfing from water–rock interaction and oxidative conditions. Calculations of deep aquifer temperature using Na–K and quartz geothermometers show 116.8–131.1° C and 82.2–125.8°C respectively. Presence of deep faults both with abnormal thermal gradient (∼45–50 K/km) define unique geochemical shape of thermal waters of Sikhote–Alin, area, where no present volcanic activity is registered.

The distribution and geochemistry of rare earth elements (REE) in anthropogenic, technogenic and natural surface waters of southern and eastern Primorye, Far East of Russia, are presented in this study. The obtained results indicated that most of REE (up to 70%) were transported as suspended matter, ratio between dissolved and suspended forms varing from the source to the mouth of rivers. It is shown that all REE (except Ce) in the source of the rivers are predominantly presented in dissolved form, however, the content of light and heavy REE is different. Short-term enrichment of light rare earth elements (LREE) caused by REE-rich runoff from waste dumps and mining is neutralized by the increase in river flow rate. Rivers in urban areas are characterized by high content of LREE in dissolved form and very low in suspended one.

Analysis of the distribution and fractionation of rare earth elements in the groundwater of the Sikhote Alin fold region reveals that their concentrations, geochemistry, and fractionation ability vary in different groundwater types depending on many factors, including the pH–Eh parameters and mineralization of the solutions and the composition of the host rocks. The results of monitoring of changes in the REE concentrations in the groundwater of the region over ten years provides the opportunity to establish the range of their variations. Inorganic forms of REE migration are rated for all geochemical types of water in the meteoric–surface–ground water system.