Distributions and Geochemical Behaviors of Oxyanion-Forming Trace Elements and Uranium in the Hￃﾶvsgￃﾶl-Baikal-Yenisei W

Journal of Geochemical Exploration 188 (2018) 123–136 Contents lists available at ScienceDirect Journal of Geochemical Exploration journal homepage: www.elsevier.com/locate/gexplo Distributions and geochemical behaviors of oxyanion-forming trace T elements and uranium in the Hövsgöl–Baikal–Yenisei water system of Mongolia and Russia Akihito Mochizukia,1, Takahiro Murataa, Ko Hosodaa, Toshiya Katanob, Yuji Tanakab, Tetsuro Mimurac, Osamu Mitamurad, Shin-ichi Nakanoe, Yusuke Okazakie, Yuko Sugiyamaf, Yasuhiro Satohg, Yasunori Watanabeh, Ayuriin Dulmaai, Chananbaatar Ayushsureni, ⁎ Darmaa Ganchimegj,2, Valentin V. Druckerk, Vladimir A. Fialkovl, Masahito Sugiyamaa, a Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan b Faculty of Marine Science, Tokyo University of Marine Science and Technology, Tokyo 108-8477, Japan c Graduate School of Science, Kobe University, Kobe 657-8501, Japan d Faculty of Education, Shiga University, Otsu 520-0862, Japan e Center for Ecological Research, Kyoto University, Otsu 520-2113, Japan f Faculty of Science, Okayama University of Science, Okayama 700-0005, Japan g Faculty of Science, Yamagata University, Yamagata 990-8560, Japan h Faculty of Geo-Environmental Science, Rissho University, Saitama 360-0194, Japan i Institute of Biology, Mongolian Academy of Sciences, Ulaanbaatar 210351, Mongolia j Institute of Chemistry and Chemical Technology, Mongolian Academy of Science, Ulaanbaatar 210351, Mongolia k Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia l Baikal Museum, Siberian Branch, Russian Academy of Sciences, Listvyanka, Russia ARTICLE INFO ABSTRACT Keywords: We investigated the distributions and geochemical behaviors of two oxyanion-forming elements: vanadium (V) Vanadium and molybdenum (Mo), and of uranium (U) in the Hövsgöl–Baikal–Yenisei water system. The vertical profiles of Molybdenum these elements in Lakes Hövsgöl and Baikal were almost constant, except V showed slightly lower concentrations Uranium in the epilimnion, probably because of biological activity. Based on residence time calculations, it is inferred that Lake Hövsgöl V and U are removed from Lake Baikal via some biogeochemical processes, whereas Mo is almost nonreactive Lake Baikal within the lake. Such differences might be attributable to their adsorptive behaviors onto solid phases, including Hövsgöl–Baikal–Yenisei water system sediments and suspended particles. The dissolved concentrations of these elements showed similar variation in the Egiin Gol and Selenga Rivers, and the highest concentration within these rivers was observed after the confluence of the Orkhon River, a tributary of the Selenga River. The concentrations in the Angara River were almost constant along its length. On the other hand, in the Yenisei River, the inflow of a tributary (the Nyzhnyaya Tunguska River) strongly affected the distributions of the trace elements. The concentrations of V and Mo at several sampling stations, particularly on the Selenga and Orkhon rivers, exceeded the maximum permitted concentration of Russian fishing industry regulations (MPCfish). The high concentrations in the Orkhon River might be attributable to pollution, whereas those in the Selenga River are probably natural because its watershed has been affected little by mining and other anthropogenic activities. 1. Introduction changes in the biogeochemical conditions of aquatic environments. For example, the chemical forms and concentrations of redox-sensitive The distributions and behaviors of trace elements in natural waters elements such as Mn and Fe change in response to the redox condition are of great interest because they often reflect minute as well as major of the water (e.g., Davison, 1993), and distribution profiles of bio- ⁎ Corresponding author. E-mail address: [email protected] (M. Sugiyama). 1 Present address: Horonobe Underground Research Center, Japan Atomic Energy Agency, Hokkaido 098-3224, Japan. 2 Deceased. https://doi.org/10.1016/j.gexplo.2018.01.009 Received 17 April 2017; Received in revised form 30 November 2017; Accepted 14 January 2018 Available online 31 January 2018 0375-6742/ © 2018 Elsevier B.V. All rights reserved. A. Mochizuki et al. Journal of Geochemical Exploration 188 (2018) 123–136 elements such as P and N are sensitive to biological activity (e.g., Horne stems from Lake Hövsgöl, the largest freshwater body in Mongolia, and and Goldman, 1994). Concentrations of trace elements and their spa- it flows to the Arctic Ocean via Lake Baikal, the largest freshwater body tiotemporal variations in rivers have been investigated in order to un- in the world, and several large man-made reservoirs. This system ex- derstand their sources, fluxes to the ocean, and the factors controlling tends up to 5500 km and therefore, environmental conditions such as their behaviors in the hydrosphere (e.g., Shiller and Boyle, 1987; climate, geological features, and hydraulic conditions differ along its Palmer and Edmond, 1993; Johannesson et al., 2000). length, which makes it suitable for investigating the influences of such Oxyanion-forming trace elements exhibit unique distributions and conditions on the behaviors of trace elements. In particular, this water 2− behaviors in limnetic areas. They exist as anions (for example, HVO4 system shows relatively higher values of pH, calcium ion concentration, 2− for V and MoO4 for Mo) in oxic and neutral to slightly alkaline waters and alkalinity due to the dissolution of carbonate rocks in the upstream and they usually show conservative behaviors in lakes and rivers (Nojiri area (Goulden et al., 2006). Such characteristic water chemistry might et al., 1985; Johannesson et al., 2000). However, their concentrations facilitate oxyanion-forming elements to exhibit higher concentrations can vary significantly in response to changes in water pH (Fuller and (Johannesson et al., 2000) and allow U to form soluble complexes with Davis, 1989; Harita et al., 2005; Carling et al., 2011) because their calcium and carbonate ions (Langmuir, 1978; Dong and Brooks, 2006). adsorptive behaviors onto various metal (hydr)oxides are strongly af- In the present study, the spatial distributions of two oxyanion- fected by pH (Dzombak and Morel, 1990). In addition, many of these forming trace elements, V and Mo, and of U in the elements are redox-sensitive (e.g., As, Sb, Mo, and V) and their con- Hövsgöl–Baikal–Yenisei water system were investigated. We de- centrations can change drastically in anoxic environments (e.g., van der termined the concentrations of both major ions and trace elements in Weijden et al., 1990; Elbaz-Poulichet et al., 1997). the entire water system. From these data, we discuss those factors that Uranium is another trace element that exhibits characteristic be- control the distributions and behaviors of these trace elements. havior in aquatic environments. Although U does not form oxyanions, it 2− typically exists as uranyl-carbonate complexes of UO2(CO3)2 and 2. Study area 4− UO2(CO3)3 (Langmuir, 1978) and as calcium-uranyl-carbonate 2− 0 complexes of CaUO2(CO3)3 and Ca2UO2(CO3)3 (aq) (Dong and The overall view of the Hövsgöl–Baikal–Yenisei water system and a Brooks, 2006; Mochizuki et al., 2015), some of which are anionic. Si- diagram of the sampling stations are shown in Fig. 1. Lake Hövsgöl milar to oxyanion-forming elements, the adsorption of U onto metal (50°27′N–51°37′N, 100°51′E–101°47′E), the origin of this water system, (hydr)oxides is pH-dependent (e.g., Hsi and Langmuir, 1985; Fox et al., has a maximum depth of 262 m, capacity of 381 km3, and is the largest 2006) and thus, the concentration of U in natural waters can vary in freshwater lake in Mongolia (Goulden et al., 2006). It is characterized response to water pH (Carling et al., 2011; Mochizuki et al., 2016). by extremely clear water and little anthropogenic influence, and it is Uranium is also redox-sensitive (Langmuir, 1978) and its concentration classified as an ultra-oligotrophic lake (Goulden et al., 2006). The single can decrease significantly in anoxic conditions where U (VI) is reduced outflowing river from the lake is the Egiin Gol River, whose outflow − to U (IV) (e.g., van der Weijden et al., 1990). rate has been estimated as 20 m3 s 1 (Goulden et al., 2006). The Egiin Given the aforementioned characteristics of oxyanion-forming ele- Gol River joins the Selenga River 270 km southeast of the lake. The ments and U, the Hövsgöl–Baikal–Yenisei water system is considered an Selenga River has its source near the Hangai mountain range in Central ideal site for studying their geochemical behaviors. This water system Mongolia and it flows eastward. After joining the Egiin Gol River, this (a) (b) H9 L. Hövsgöl N Kara Sea H10 Upper Angara R. H11 H12 200 km 55° N H2 H3 H1 H4 H8 H7 H5 H6 H17 L. Baikal Barguzin R. H15 H16 (d) H14 Turka R. H13 LS14 N LS12 LS11 B1 Uda R. LS13 LS10t Uul Nuer R. LS5t 500 km Temnik R. L. Hövsgöl LS9t Khilok R. 60° N Dzhida R. LS2t US1 US4t Chikoi R. US2 US5 US9 50° N US3 US6 Angara R. (c) Egiin Gol R. US8 US10t Selenga R. Orkhon R. US7t Selenga R. 100° E 105° E 110° E (b) Selenga R. LS8 Yenisei R. LS6 Russia LS4 LS7t 50° N Mongolia LS3 LS1 US11 Chikoi R. 100° E 110° E Orkhon R. Fig. 1. (a) Overall view of the water system. Location of sampling stations in (b) Lake Hövsgöl, Egiin Gol River, Selenga River, and Lake Baikal, (c) Angara River, and (d) Yenisei River. Stations UY6 and UY7 are located on the left and right banks of the Yenisei River, respectively. Station UY16t is located on a small tributary, the Kureika River. 124 Download English Version: https://daneshyari.com/en/article/8865993 Download Persian Version: https://daneshyari.com/article/8865993 Daneshyari.com.

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