Hydrochemical regime of saline lakes in the Southeastern Transbaikalia

Geography and Natural Resources 31 (2010) 370–376

Hydrochemical regime of saline lakes in the Southeastern Transbaikalia L. V. Zamana * and S. V. Borzenko Institute of Natural Resources, Ecology and Cryology SB RAS, Chita Received 25 February 2010

Abstract Results from hydrochemical investigations into macrocomponent composition of some of the lakes in the Southeastern Transbaikalia are presented. The region’s saline lakes, as a rule, are soda-chloride or chloride-soda lakes according to their chemical composition. The lakes’ hydrochemistry is determined by a combination of evaporative concentration of salt composition, intra-water body hydrobiological processes, especially by the production of organic matter and reduction of sulfates as well as by hydrogenic sedimentation. Keywords: saline lakes, evaporative concentration, hydrobiological processes, hydrogenic mineral formation.

In the southern part of the Eastern Transbaikalia and on the neighboring territories of Mongolia and China there occur numerous brackish and saline lakes, the hydrochemical characteristics of which, along with their spatial inhomogeneity, have been and are undergoing significant chronological changes. The reason behind such changes has to do with the cyclic fluctuations of the climatic conditions which cause an intermittent impounding and drying of the lakes. The total water surface of the largest, interconnecting lakes, Barun-Torei and Zun-Torei, reaches 850 km2 during abundant-water periods. Based on long-term water level observations, it is possible to identify intrasecular cycles with a duration from 8–10 to 35 years. In the 20th century, the Torei Lakes dried up almost entirely in 1903–1904, 1921–1922 and 1944–1947, while their largest impounding was recorded in 1963–1965 and 1993–1995 [1]. According to fragmentary historical evidence, the Torei Lakes dried up also in the 18th–19th centuries [2]. Within the last 50 years, a full cycle of variation in the territory’s atmospheric humidification lasted 34 years (from 1965 to 1998) and had equal (in duration) phases of aridization (till 1981) and humidification. The current aridity phase of climatic conditions superseding it is accompanied by a more than 1 °С air temperature rise during the summer months against the corresponding phase of the previous * Corresponding author. E-mail addresses: [email protected] (L. V. Zamana), [email protected] (S. V. Borzenko).

cycle. This has led to an increase in evaporation from the water surface, and to a dramatic decrease (with a very low amount of atmospheric precipitation) in the overall humidification of the territory [3]. A survey done in the summer of 2006 showed that half of the lakes in the south of the Eastern Transbaikalia were found to be dried up, although only 8 years had elapsed from the last long-term maximum of precipitation. The incipient increase in atmospheric humidification notwithstanding, the drying up of the lakes was still in progress during 2007–2009. The orographic and geologo-structural location of the lakes The saline lakes of the Southwestern Transbaikalia form part of the Amur catchment basin and of the Torei drainless region which stands out in isolation within its boundaries. A large number of the lakes under consideration are clustered within the confines of the Tsachuseiskaya depression which is located in the middle part of the Onon river and extending from the Mongolian border northward to 100–110 km. The surficial deposits of the depression are represented by Mid-Pleistocene sandshale depositions in the form of a whitish layer up to 100 m thick which overlap the effusivesedimentary Mesozoic rocks, in some places outcropping on the day surface in the immediate vicinities of the Torei lakes. The surface of the depression is complicated by hollows and ridges. According to the current views, their origin is associated with a catastrophic hydraulic outburst

Copyright © 2010 IG SB, Siberian Branch of RAS. Published by Elsevier B.V. All rights reserved doi:10.1016/j.gnr.2010.11.011

L. V. Zamana and S. V. Borzenko / Geography and Natural Resources 31 (2010) 370–376

(jökulhlaup) in Eastern Asia [4]. The hollows extend along a southeastern direction to hundreds of meters, and most of them are as deep as 10 m. During humid periods they are occupied by brackish and saline lakes. The ridges have about the same extent, with their height ranging from a few meters to 20–25 m. In the northeastern surroundings of the hollow, along the left bank of the Borzya river, a scarp of terrigenous-carbonate Devonian rocks, encircled by a chain of lakes, rises 60 m above the hollow bottom. Beyond the Tsachuseiskaya depression, in its northern surroundings, the zones of occurrence of Mesozoic igneous rocks include Lake Kharaganash and Lake Shalota, with Lake Nozhiy located in the area of metamorphic Paleozoic strata. In addition to Lake Kholboldzhe that is situate don the southeastern slope of the Borshchovochny range, the lakes areal classified with the Onon-Borzya group [5], with the number of brackish and saline lakes being more than one hundred, even at periods of droughts. The spatial distribution of the lakes of different salinity and different chemical types does not show any definite regularity; every so often, lakes with waters of a different composition and mineralization are separated by small distances, but they are all localized in the zone of arid climate and are devoid of overland runoff. Methods and results of hydrochemical investigations The hydrochemical investigations into the macrocomponent composition of some of the lakes were made during 2006–2008 (Table 1). Chemico-analytical measurements of water samples were carried out by following generally accepted techniques. Calcium and magnesium concentrations were quantified by the atomic absorption method in argon-acetylene flame with the SOLAAR 6M spectrophotometer. The flame-emission method was used in sodium and potassium determination. The determination of pH, Eh, Cl− and F− was carried out potentiometrically by using ion-selective electrodes. Titration was used to determine the CO3− and HCO3− contents, and the value of permanganate oxidizability. The sulfate ion was determined turbidimetrically in the form of barium sulfate. The measurement errors for the concentration of the components met the requirements of GOST 27384–87. The salinity of the lakes is due to concentration of their waters under an arid climate implying a directional of their chemical composition, with the chemical type changing from the carbonate through sulfate to chloride type [5]. Such a consecutive change in chemical composition is accounted for by the deposition of salts a they are saturating the lakes’ waters; first come the least soluble calcium and magnesium carbonates, followed by calcium sulfates, and so on. As suggested by O. A. Sklyarova and collaborators [6], the hydrochemical evolution of the mineral lakes in the Priolkhonie region differs from Kurnakov’s scheme of direct metamorphization and is proceeding in the form of two

371

alternative sequences: (HCO3)–(Ca, Mg, Na) → (HCO3)–(Mg, Na) → (HCO3)–(Na) ; (HCO3, SO4)–(Ca, Mg, Na) → (HCO3, SO4)–(Mg, Na) → (SO4, HCO3)–(Mg, Na) → (SO4, Cl)–(Mg, Na) → (Cl)–(Na) . In these schemes, when evaporating, hydrocarbonate waters transform according to the carbonate (soda) type, while hydrocarbonate-sulfate waters transform according to the chloride (halite) type. The reasons behind the differing directedness of the change in composition of the lakes’ waters, with an increase in their salinity, are not discussed in this study. The actual distribution of the chemical components in the waters of the lakes of the Southwestern Transbaikalia under investigation differs from the aforementioned metamorphization schemes (see Table 1). Only in the least mineralized Lake Kolosun-Nor, with its salinity of 1.35 g/L, the anion composition of water was of the hydrocarbonate type proper, whereas in the other lakes the chlorine ion was predominant or came second in significance. Furthermore, carbonates were dominant in relatively slightly mineralized waters, with their salinity not exceeding 11.1 g/L. For a number of lakes, chlorine was the main anion during early concentration stages of brine following its saturation for calcium carbonates which usually sets in when natural waters have a mineralization of 0.7 g/L, and the pH value is 7.4 [7]. Sulfates were used in the determination of the chemical type of water only in three cases (ions with at least 20%-eq. content are involved in the designation of the type), but they were in subordinate amounts, although, in line with the general views, in the mineralization range under investigation they must be the man components of the ion composition of lacustrine waters. An illustrative example of the relationship of anions in the waters of the aforementioned lakes is provided in Fig. 1. Accelerated growth of chlorine ion content in lacustrine waters corresponds to the relationship of major anions in subterranean water in the zone of continental salinization [7] which make the main contribution to salt alimentation of the lakes. Its equivalent concentrations are, on the average, higher when compared with sulfate. Therefore, even prior to the saturation of brine with sulfate minerals and their precipitation, in the general case the sulfate ion cannot be the major anion for the waters of brackish lakes. Hence the formation of sulfate waters proper is possible providing that there are additional sources supplying sulfates to the lake. Thus, for the Alginskiye Lakes in the Barguzinskaya depression they are the waters of the thermal spring feeding them; for the lakes of the intermontane depressions of the Western Transbaikalia they are represented by the sulfate waters from deep horizons occupying the hollows of Mesozoic sedimentary-terrigenous deposits [8] containing iron sulfides (pyrite, and marcasite), and it is their oxidation

3

8.61

9.18

9.02

9.30

9.38

9.43

9.32

9.32

9.56

9.32

9.25

9.72

9.46

9.52

9.54

2

Kolosun-Nor, 09.08.2006

Nozhiy, 11.05.2008

Narym-Bulak, 08.08.2006

Narym-Bulak, 08.09.2008

Kuduk, 10.08.2006

Kholboldzhe, 14.04.2007

Shalota, 10.08.2006

Bain-Tsagan, 08.08.2006

Zun-Torei, 26.08.2008

Kharaganash, 10.08.2006

Kunkur, 11.08.2006

Zun-Torei, 23.03.2008

Bol. Yakshi, 08.08.2006

Mal. Yakshi, 08.08.2006

Barun-Torei, 09.08.2006

1

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

рН

Lake, sampling date

Sample number

22

50

41

5

121

47

56

97

60

–

99

140

96

192

64

4

Eh, mV

–

85.7

104.6

–

24.0

38.6

–

18.5

54.8

21.2

109.4

–

30.1

–

52.8

5

840

900

600

510

240

600

510

240

285

273

300

69

72

30

42

6

СО32−

1769

2074

1647

2013

1007

1739

1403

1251

1586

1244

1220

878

854

628

799

7

НСО3

1128

260

397

560

1480

790

448

206

490

170

396

196

194

180

86

8

SO42

2513

2400

2292

1173

1319

447

1000

1260

563

1093

398

1023

1049

128.9

59

9

Cl−

8.29

12.0

8.68

8.29

3.79

2.75

7.92

4.16

1.81

1.44

2.50

4.16

3.15

3.15

4.77

10

F−

2.8

3.7

3.5

6.7

3.7

4.0

6.9

3.1

2.9

39.3

2.7

18.7

19.0

29.4

116.1

11

Ca2+

79.7

169.3

74.3

66.9

100.5

165.4

56.4

38.7

177.8

161.3

67.0

63.1

52.0

48.8

89.7

12

Mg2+

3320

2700

2510

2089

1859

1386

1686

1418

1000

1034

990

980

1030

290.5

140.8

13

Na+

40.4

140.4

87.1

27.2

92.5

132.4

15.4

54.5

144.5

35.8

18.5

20.8

15.1

18.5

7.9

14

K+

9701

8659

7620

6451

6106

5267

5126

4476

4251

4061

3395

3189

3271

1357

1345

15

Sum of ions

Chemical composition of water from mineral lakes (components and sum of ions, mg/L)

Cl − 46.8НСО3 − 37.7 Na + 94.9

Cl − 49.3НСО3 − 46.7 Na + 97.0

Cl − 53.9НСО3 − 39.2 Na + 92.7

НСО3 − 52.5Cl − 34.7 Na + 93.2

Cl − 40.2SO42 − 33.4НСО3 − 26.4 Na + 88.1

НСО3 − 62.6SO42 − 21.2 Na + 77.6

НСО3 − 51.3Cl − 36.2 Na + 93.1

Cl − 52.0НСО3 − 41.7 Na + 98.8

НСО3 − 57.6Cl − 25.8 Na + 70.0Mg 2+ 23.8

Cl − 48.2НСО3 − 46.2 Na + 73.4Mg 2+ 21.9

НСО3 − 60.6Cl − 22.7 Na + 87.4

Cl − 59.6НСО3 − 29.8 Na + 86.5

Cl − 54.8НСО3 − 36.5 Na + 90.4

НСО3 − 59.9SO42 − 20.0 Na + 67.8Mg 2+ 21.8

НСО3 − 79.7 Mg 2+ 38.1Na + 31.2Ca29.6

16

Kurlov’s formula

Table 1

372 L. V. Zamana and S. V. Borzenko / Geography and Natural Resources 31 (2010) 370–376

9.48 Zun-Kholvo, 10.08.2006 22

Note. PO – permanganate oxidizability. In Kurlov’s formula, the sum of НСО3− and СО32− is given under НСО3−. Dash – no determinations. Chemico-analytical investigations were made by S. V. Borzenko, T. G. Smirnova and T. E. Khvostova.

Cl − 55.9НСО3 − 33.6 Na + 98.3 45093 243.2 16120 70.7 4.8 25.1 14166 3970 6893 3600 174.1

9.18 Gorbunka, 25.08.2008 21

48

Cl − 80.7 Na + 91.5 41336 77.6 14720 681.5 18.6 2.39 19019 6424 354 42 51.0

9.09 Khilganta, 25.08.2008 20

–

Cl − 68.3SO42 − 30.7 Na + 86.9 16849 20.9 5514 416.6 17.7 1.58 6764 4116 151 12 14.2

9.52 Dorbon-Torum, 09.08.2006 19

–

Cl − 54.8НСО3 − 29.7 Na + 86.9 15398 133.8 5069 132.2 3.2 6.00 5613 920 2501 1020 54.8

9.51 Tsagan-Torum, 08.08.2006 18

65

Cl − 65.1НСО3 − 30.4 Na + 95.8 13328 95.4 4656 74.4 2.8 7.92 5003 472 2056 960 65.1

9.53 Ulan-Nor, 09.08.2006 17

137

Cl − 53.6НСО3 − 33.9 Na + 94.1 13202 42.1 4546 133.4 3.0 9.97 3992 1260 2135 1080 13.0

11147 6.6 3700 97.1 3.1 15.1 1996 960 2989 1380 61.7 34 9.56 Sagan-Nor, 10.08.2006 16

77

НСО3 55.5Cl − 32.8 Na + 95.0

16

−

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

Table 1 continued

L. V. Zamana and S. V. Borzenko / Geography and Natural Resources 31 (2010) 370–376

373

that is the cause for the high concentrations of dissolved sulfates. In actual truth, not only does there not occur any proportionate (with chlorides) accumulation of sulfates in the waters of the lakes under study, but they lag behind as regards the accumulation rates, while the contents of hydrocarbonate and carbonate are increasing more intensely in most cases when compared with them. Such a situation is inconsistent with the general views and calls for a separate treatment. A thermodynamical modeling for two springs feeding Lake Kharaganash and Lake Kuduk which was carried out by using the HydroGeo 32 software package [9] showed that during evaporative concentration the change in water composition, with the possible formation of secondary mineral phases taken into account, generally corresponds to the direction of direct metamorphization but differs drastically from the data on the lakes. The initial waters had, respectively, a sulfate-hydrocarbonate magnesiumcalcium and hydrocarbonate sodium-calcium composition, with their mineralization amounting to 328 and 332 mg/L. The calculated residual compositions of solutions for the case of concentration of the waters from the springs to a level of chlorine content in the water of the lakes (used as the concentration index for the initial natural solutions) were represented as the %-equivalent expression by the relationships: SO42 −50.4 HCO3−31.3 for the spring near Lake Kharaganash, and SO42 −60.7 Cl−28.4. for the spring near Lake Kunduk. Further, the calculated sulfate contents were higher (1697 and 1288 mg/L, respectively), and the sums of hydrocarbonate and carbonate (1338 and 115 mg/L) were lower than the actual ones in the lakes’ brine. In the composition of equilibrium phases, the main components were represented by calcium, dolomite, and quartz as well as gypsum for the first spring which was virtually absent in the composition of the possible hydrogenous minerals in the case of water concentration for the second spring with lower initial concentrations of sulfates. Accumulation of carbonate components in the lakes’ waters at the expense of the initial concentrations in the feeding springs is possible in the case where the inequality rHCO3− + rCO32− > rCa2+ + rMg2+ holds, where r is the equivalent form of concentration. In the spring near Lake Kharaganash, the sum of carbonate components was only slightly higher than that of alkaline-earth elements; in the latter case, their relationship was the reverse, which was reflected in a regular fashion in the modeling results. The reasons for the difference between the calculated and actual concentrations and relationships of anions are attributable to the following factors. In subterraneous waters of the hypergenesis zone, including of the continental salinization region, which have a dominant role in the water alimentation of the lakes, the sum of chemical equivalents of Ca and Mg is, on the average, larger than that of the H2CO3 ions [7]. Under such conditions, accumulation of carbonate components to a level significant for determining the chemical type of the waters is only possible if there are their additional sources. For

374

L. V. Zamana and S. V. Borzenko / Geography and Natural Resources 31 (2010) 370–376

Fig. 1. Relationship of major anions (BА) in the lakes’ brine (according to sample numbers, see Table 1). 1 – sum of НСО3− and СО32−; 2 – SO42−; 3 – Cl−.

brackish and saline lakes the inputs of the hydrochemical balance of carbonates are comprised of the portion supplied together with the subterranean and overland runoff as well as the portion provided by the mineralization of organic matter (OM), both dissolved and accumulating in bottom sediments. Their high concentrations in the lacustrine waters are evidenced by the values of permanganate oxidizability (see Table 1). One of the OM sources is provided by detritus which undergoes bacterial destruction; it arrives from catchments as well as being produced in the water bodies themselves by algal communities. It is thought that the overwhelming bulk of detritus is allochthonous [10]; it arrives from catchments; in many cases, however, the major portion of detritus accumulates in the water bodies themselves as a result of dying algae which occur widely within the inshore area of most lakes. Generation of organic carbon within the water column itself as a result of bacterial photosynthesis is an equally important, if not a key, factor. In the surface horizons of the saline lakes of the Southwestern Transbaikalia, the total production of OM by bacteria and algae for a summer season is estimated at 0.23–33.6 mg C/(m2·day) [11]. The delay in accumulating the sulfate ion in the lacustrine waters, and, not infrequently, its removal from them are also associated with the microbiological processes. This occurs exclusively as a consequence of the sulfate reduction processes because, as thermodynamical calculations show, the lakes’ brine is not saturated as regards gypsum. Sulfate reduction is also taking lace intensely both in bottom sediments and in the water column. In chloride-soda Lake Doroninskoye, some time intervals showed up to 50 mg/L of hydrogen

sulfide [12]. Its formation was also reliably documented in the near-surface oxygen-containing water layer. Among the lakes under consideration, judging by a strong odor of H2S, and by the presence of black silty mud deposits, sulfate reduction is manifested at the most in Lake Ulan-Nor and Lake Zun-Kholvo. Among the microbiologically explored lakes: Barun-Torei, Gorbunka, and Khilganta, the sulfate reduction process was taking place most intensely in the first of them, with the sulfate reduction rate in the cyanobacterial mat reaching 12.0 mgS/(dm3·day) [13]. A donor for electrons in this case was provided by OM carbon which transforms to CO2 and enters the water column. An important factor of formation of the lakes’ hydrochemistry is provided by sedimentation associated with the saturation of water according to definite mineral phases. According to data of thermodynamical calculations, the lakes are characterized by the carbonate type of sedimentation (Table 2); the composition of hydrogenous depositions can include minor amounts of hydroxides (gibbsite, and boehmite), clay minerals (montmorillonites, and illites), zeolites (wairakite), and others. Judging from Lake Doroninskoye, bottom sediments in the case of sulfate reduction contain metal (notably iron) sulfides. Fine-disperse sulfide muds have a special value as a balneological resource. In spite of a rather high (in some cases) brine salinity in the lakes, the gypsum stage of mineral formation does not set in, which is mainly due to the mobilization of calcium by carbonate minerals. The hydrochemical regime of the lakes during the time interval under investigation is assessed, having regard to the other water bodies on this territory, as being closely

L. V. Zamana and S. V. Borzenko / Geography and Natural Resources 31 (2010) 370–376

correlated with the period of the highest climate aridity for the last 50–60 years. The comparison with the year 1987 for 8 lakes when an increase in climatic humidification was taking place, showed that salinity in most of the lakes increased (by a factor of 5–7 at a maximum) at the beginning of the current century. On the other hand, some instances of its decrease were observed (Fig. 2). Particularly noteworthy is the oppositely directed character of variation in water

375

salinity in Lake Barun-Torei and Lake Zun-Torei within the period under consideration. In the latter lake (the end runoff basin in the system of these lakes), in some time intervals of hydrological cycles there can occur the hydrochemical regime which will be the inverse of the prevailing regime for the region’s saline lakes, and this should be taken into consideration in palaeoclimatic reconstructions.

Table 2

Some equilibrium mineral phases for 600 lakes as deduced from thermodynamic estimation of the Table 1 data using the HG32 program [9] Lake

Saturation for mineral phases, mg/L 1

2

3

4

5

Kolosun-Nor

402.8

0.003

0.012

–

0.111

Kuduk

12.4

135.8

–

–

0.109

Shalota

10.34

226.6

230.3

–

1.68

Kharagahash

15.01

303.4

220.3

3.2Е–6

0.66

Zun-Torei

31.84

139.2

0.002

5.1Е–6

0.03

Barun-Torei

12.83

131.7

178.1

1.1Е–6

0.15

Sagan-Nor

14.12

315.1

0.005

2.8Е–6

0.07

Tsagan-Torum

12.83

196.3

0.004

2.2Е–6

8.3–6

Dorbon-Torum

14.18

280.4

203.9

–

0.30

Zun-Kholvo

22.84

163.6

0.003

6.4Е–6

5.0Е–6

Note. Mineral phases: 1 – dolomite CaMg(CO3)2; 2 – hydromagnesite Mg5(CO3)4(OH)2·4H2O; 3 – lansfordite MgCO3·H2O; 4 – calcite СаСО3; 5 – whitlockite Са9Р6О24.

Fig. 2. Change in lakes’ water mineralization for two sampling periods. 1 – 12–14 July 1987, 2 – 9–11 August 2006.

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L. V. Zamana and S. V. Borzenko / Geography and Natural Resources 31 (2010) 370–376

Conclusion Thus the formation and transformation of chemical composition of water from saline lakes in the zone of continental salinization is a multifactor process in which, along with evaporative concentration, hydrobiological processes and sedimentation are taking place within the water body. The content of carbonate components in the waters of saline lakes depends on the functioning of the microbial community in a particular water body. Evaporite sedimentation sets limits on the accumulation of many components in the waters, but bacterial production of carbonate assemblages in the case of conjugate sulfate reduction permits them to concentrate in significant amounts to the extent that soda waters or chloride-soda waters are formed. Dominance of a particular process in the salt composition formation determines the hydrochemical diversity of saline lakes. This work was done with financial support under the SB RAS project (No. 38 “Mineral Lakes of Central Asia – archives of palaeoclimatic high-resolution records and renewable liquid ore”). References 1. Zamana L. V. and Obyazov V. A. Dynamics of the level and hydrochemical regimes of the Torei Lakes in the 20th century. Scientific Foundations of the Preservation of Catchment Basins: Interdisciplinary Approaches to Natural Resources Management: Abstracts of Papers to the International Conference (Ulan-Ude (Russia) – Ulan Bator (Mongolia), 1–8 September 2004) in 2 volumes. Ulan-Ude: Izd-vo Baikalsk. nauch. tsentra SO RAN, 2004, v. 1, pp. 98–99. 2. Krendelev V. A. Periodicity of impoundment and drying of the Torei Lakes (Southeastern Transbaikalia). Dokl. AN SSSR, 1986, v. 287, No. 2, pp. 396–400. 3. Obyazov V. A. Variation in air temperature and humidification of the territory of the Transbaikalia and the border areas of China. In: Nature Conservancy Cooperation Between the Chita

Region (RF) and the Inner Mongolia Autonomous Region (China) in Transboundary Ecological Areas: Conf. Proc. (Chita, 29–31 October 2007). Chita: Izd-vo Zabaikalsk. gumanit.-ped. un-ta, 2007, pp. 247–250. 4. Sklyarov E. V., Sklyarova O. A., Menshagin Yu. V., and Levin A. V. Eurasian catastrophic floods: Tsachuseisky jökulhlaup of the Southern Transbaikalia. Dokl. AN, 2007, v. 415, No. 4, pp. 544–547. 5. Vlasov N. A., Chernyshov L. A. and Pavlova L. I. Mineral lakes. In: Mineral Waters of the Southern Part of Siberia. V. 1: Hydrogeology of Mineral Waters and Their Significance for the National Economy. Ed. by V. G. Tkachuk and N. I. Tolstikhin. Moscow; Leningrad: Izd-vo AN SSSR, 1961, pp. 189–245. 6. Sklyarova O. A., Sklyarov V. E., Fedorovsky V. S., and Sanina N. B. Mineral lakes of the Olkhon region: questions of genesis and evolution. Geography and Natural Resources, 2004, No. 4, pp. 44–49. 7. Shvartsev S. L. Hydrogeochemistry of the Hypergenesis Zone. 2nd corrected and enlarged edition. Moscow: Nedra, 1998, 366 p. 8. Dzyuba A.A., Tulokhonov A. K., Abiduyeva T. I., and Grebneva P. I. Distribution and chemistry of saline lakes in the Pribaikalia and Transbaikalia. Geography and Natural Resources, 1997, No. 4, pp. 65–71. 9. Bukaty M. B. Software development for hydrological problemsolving purposes. Izv. TPU, 2002, v. 305, No. 6, pp. 348–365. 10. Lokot L. I., Strizhova T. A., Gorlacheva E. P. et al. Soda Lakes of the Transbaikalia. Ecology and Productivity. Ed. by A. F. Alimov. Novosibirsk: Nauka, 1991, 216 p. 11. Abiduyeva E. Yu., Syrenzhapova A. S. and Namsarayev B. B. Functioning of microbial communities in soda-saline lakes of the Onon-Kerulen group (Transbaikalia and Northeastern Mongolia). Sib. ekol. zhurn., 2006, No. 6, pp. 707–716. 12. Zamana L. V. and Borzenko S. V. Hydrogen sulfide and other reduced forms of sulfur in the oxygen water of Lake Doroninskoye (Eastern Transbaikalia). Dokl. AN, 2007, v. 417, No. 2, pp. 232–235. 13. Brackish and Saline Lakes of the Transbaikalia: Hydrochemistry, Biology. Ed. by B. B. Namsarayev. Ulan-Ude: Izd-vo Buryat. un-ta, 2009, 340 p.