Limnology (2010) 11:281–287 DOI 10.1007/s10201-010-0313-5
ASIA/OCEANIA REPORT
Further discussion about the features of Lake Puma Yum Co, South Tibet, China Liping Zhu • Jianting Ju • Junbo Wang Manping Xie • Mitsugu Nishimura • Tetsuya Matsunaka • Hisayoshi Terai
•
Received: 23 January 2008 / Accepted: 8 January 2010 / Published online: 25 February 2010 Ó The Japanese Society of Limnology 2010
Abstract Further discussion about the limnological features of Lake Puma Yum Co, South Tibet, China, is provided based on the results of several investigations. By using depth data from all over the lake, the whole submarine topography has been compiled. Horizontal analysis of the water’s physicochemical features indicates that compared with the relatively uniform water features at other lake areas, apparent spatial heterogeneity exists in the water of the subaquatic alluvial fan induced by the Jiaqu River, the biggest inflow. Vertical analysis of water characteristics using two-factor analysis of variance with no reexperiment indicates that temperature, dissolved oxygen, and pH of the water vary with water depth rhythmically, whereas other parameters demonstrate no evident vertical variation, which shows that chemical stratification is not obvious. But this does not exclude slightly higher concentrations of Ca2? induced by lower pH at the bottom of deep lake water. The hydrochemistry difference between inflow water and lake water reveals the loss of Ca2? in lake
L. Zhu J. Ju (&) J. Wang M. Xie Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China e-mail:
[email protected] J. Ju Science in China Press, Beijing 100717, China M. Nishimura T. Matsunaka Department of Marine Science, Tokai University, Shizuoka, Japan H. Terai College of Bioscience and Biotechnology, Chubu University, Kasugai, Japan
water, which indicates calcite deposition may be an important characteristic of lake sediment. Keywords Lake Puma Yum Co Tibetan Plateau Hydrochemistry Submarine topography Spatial distribution
Introduction Lake Puma Yum Co (or Pumayum Co; in the Tibetan language, Co means lake), located in a mountain basin in the pre-Himalayas of the Tibetan Plateau, was investigated limnologically three times by Sino-Japanese teams in April 2001, August 2004, and August 2006, and one time by a Chinese team during August 2005. The preliminary results of the first field investigation were reported by the Tokai University Himalayan Expedition Committee (Nishimura and Takada 2003) and published openly (Mitamura et al. 2003). The further study based on the results of the second field investigation was also reported (Murakami et al. 2007). In those studies, some limnological features of Puma Yum Co during the circulation period and stagnation period were described. In this paper, we provide more information on the limnological features of Puma Yum Co, including the lake morphology and water physicochemical features based on the field investigation as well as laboratory analysis data. Study area Lake Pumoyum Co is a semi-enclosed lake with a water surface of less than 300 km2 (*285 km2 in the dry season and *290 km2 in the flood season according to the satellite images) in a catchment area of 1232.9 km2. There are
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four inflowing rivers around the lake, among which the Jiaqu River is the largest, deriving from the melting water in the south of the lake and accounting for 72% of all inflows (Murakami et al. 2007, Fig. 1). There is a newly excavated open channel on the east side (Fig. 1), through which water is discharged into Yamzhoyum Co, located about 40 km northward from Lake Puma Yum Co, during the high lake level period. This area is situated in the rainshadow region of the Himalayas, and the mean annual precipitation is only around 300 mm, with more than 90% occuring from June to September (Guan et al. 1984). However, the mean annual evaporation is as high as 2070 mm based on the observation of the meteorological station near Yamzhoyum Co Lake (Guan et al. 1984). The daily average evaporation was as high as 4 mm (by E601) or 5 mm (by ø20) on July 2006 according to the observations of a small hydrologic station, namely Tui, on the east bank of the lake. Therefore, inflows are essential for maintaining the lake water volume balance. Geologically, the whole catchment belongs to the Upper Triassic Period (T3ny) (Bureau of Geology and Mineral Resources of Xizang Autonomous Region 1993), where limestone, shale, and sandstone can be found. Pluvial-alluvial plains are distributed in the eastern, southern, and western shorelines of the lake, while the north lakefront forms a fault scarp.
Materials and methods Using a multiprobe sensor (Hydrolab DS5), water temperature, pH, specific conductivity (SpCond), photosynthetically active radiation (PAR), and concentration of luminescent dissolved oxygen (LDO) were measured in situ at 59 sites all over the lake (Fig. 1). Besides river samples, lake water samples were collected at every 5-m depth at one site in 2004 (Fig. 1). Many Ko n
28.65
28.6
gq u
Ri ve
KQ1-1
r
31 34 33 32
JQ
JQH2-1 JQH1-1
30 29
28
2 27 26
HK
1-1
3 4 5
25 76
4
22
23
45 4443 4241 24
21
8
XS10
28.45
K1 - 14
9 10 11 12
XSW3-1 XSW2-1
36 1
54
55
5657 59 58
3738
28.6
LW 3940
r X SH
13 14 15 16 17 18 19 20
RDW1-1 RDW2-1
Rive r
JQ1-1
Jiaqu River
JQZW2- 1
Ro n gduo
JQZW1-1
35
52 53
46 47 48 49 50 51
Xiasuo Rive
RDHK1-6
28.55
28.5
of water samples were collected in 2005, including 12 water samples taken from every inflowing river and water samples collected every 5-m depth along vertical profiles at 45 sites throughout the lake (Fig. 1). Major cations of water samples collected in 2004 were measured by ICP-AES (ULTIMA, JY Company, France), and major anions were determined by an ion chromatograph (DX100, Dinex, USA). Major cations of water samples collected in 2005 were determined with another ion chromatograph (ICS-2500, Dinex), and major anions except HCO3- were measured by ICS-2000. HCO3- concentration was estimated from the ion balance of major cations and anions. Submarine topography of the east part of the lake was detected by GPS/ultrasonic probing (depth-sounder with GPS; Honda Electronics HE-6211) in 2004 and that of other areas was detected by a single frequency Echo Sounder HD-27 with GPS receiver HD8500 (Hi-Target Surveying Instrument Co. Ltd., China) in 2005 (Fig. 2). Based on the 63327 depth data, grid data of lake depth were obtained using the Krige interpolation method in Golden Software Surfer 8.0. After filtering the grid data by a Gaussian low-pass filter, we compiled the bathymetric map. By using the same method, based on the data measured by Hydrolab DS5, the contour maps of pH and LDO of the surface water were also created. Two-factor analysis of variance with no re-experiment was used to estimate whether the hydrochemistry parameter variation (pH, Ca2?, Mg2?, HCO3-, and SpCond) was independent of the variation of depths or sampling sites, i.e., whether there was chemical stratification. At 0.01 significance level, the null hypothesis is reduced so that the value of the hydrochemistry parameters is independent of the affecting factor (depth or sampling site) if F \ Fcrit (or P-value [ 0.01), and vice versa. Nine sites with water depth more than 50 m were selected for studying the vertical variations of pH, LDO, PAR, and SpCond and three sites with water depth more than 40 m for studying the vertical distribution of ions.
DQBYW1-1
Outflo w XSW1-1
Water Sample Transect
Conductance in situ River sampling site
28.55
Island 2004 track lines
Marsh
2005 track lines
90.15
90.2
90.25
90.3
90.35
90.4
90.45
90.5
90.55
28.5
other data
90.25
Fig. 1 Map of water sampling sites. Lines of JQHK1-14, RDHK1-6, and XSHK1-14 indicate the sample transects from each river inlet to the inner lake, respectively. Little cross named LW indicates the location of the vertical water sampling profile collected in 2004
123
90.3
90.35
90.4
90.45
90.5
Fig. 2 Track lines for bathymetric survey. Beside track lines measured in 2004 and 2005, other data mean the depth data where water or/and sediment samples were taken
Limnology (2010) 11:281–287
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Results and discussion Submarine topography The bathymetric map (Fig. 3) indicates that there is a mild submarine alluvial fan with water depth less than 4 m in the west part of the lake, induced mainly by the Jiaqu River. Water with depth less than 2.6 m on that fan appears to be as turbid as the Jiaqu River, contrary to the bright green water in the open lake area. However, there are no alluvial fans in the other inlets. Therefore, the Jiaqu River has a great influence on the submarine topography because of its large flux. Similar to the morphology on land, the submarine slopes are gentle in the east and south of the lake compared with the steep submarine slope north of the lake. The submarine topography is fairly flat and has a depth deeper than 50 m in the center of the lake. The maximal depth reading obtained by the echo sound was 73.75 m, located among three islands. Hydrochemistry of inflowing rivers Except the three little streams, the composition of major cations of inflows is Ca2? ›Mg2? ›Na?››Sr2? ›K?, and the anions are also in decreasing order as HCO3-›SO42-››Cl(Table 1). It is evident that significant differences exist in the chemistry of the input water. In the maximal river, the Jiaqu River, the total dissolved solids (TDS) concentration is as low as 54.22 mg l-1 (Table 1). Horizontal variation of hydrochemistry characteristics of lake water The pH and LDO of most lake water are fairly homogeneous horizontally, except the water on the alluvial fan, where data are lacking for the two parameters (Fig. 4). The pH varies from 8.76 to 9.86 and has a mean value of 9.32. Unfortunately, we put in incorrect barometric pressure data when calibrating the LDO probe of the instrument. But the mistake had no influence on the spatial comparison. In the shallow water area, the LDO appears comparatively higher, which may be induced by the stronger disturbance of the wave.
60
40
30
20
28.6
50
28.55
Submarine alluvial fan 28.5
20
Isobath 90.25
90.3
90.35
90.4
90.45
Fig. 3 Isobath map of Lake Puma Yum Co (m)
90.5
The major cations in the water of the broad area of Puma Yum Co are, in decreasing order, Mg2?›Ca2?›Na?›› K?›Sr2?, and the anions are HCO3-›SO42-››Cl- (Table 1). Even in the whole lake, there is also a considerable difference between the western alluvial fan and the broad lake area (Table 1). The ion composition of the former area looks more like inflowing water. Water ion characteristics of the surface water in three lake bays, JQHK, RDHK, and XSHK, were analyzed along three transects (for positions, see Fig. 1; for results, see Fig. 5). Comparing other bays, the chemistry of water in JQHK, where the Jiaqu River flows into the lake, is characterized by obvious spatial heterogeneity (Fig. 5a, d). The concentrations of ions and TDS increase in the offshore direction. In the central lake water, the concentrations of Mg2? and Na? become the first and the second predominant ions in cationic composition, unlike inshore water and Jiaqu River water. The TDS isoline map (Fig. 6) of the lake also shows horizontally heterogenous distribution at the western part of the lake. The spatial variations of water ions indicate that Jiaqu River has more broad influences on the ion spatial hydrochemistry distribution of lake water. Comparison of chemical composition between river water and lake water at different parts of the lake indicates the variation of Ca2? concentration as well as the TDS difference. The TDS difference between rivers and the lake (54 and 290 mg l-1 in the Jiaqu River and the major part of the lake, respectively) may result from intensive evaporation in this area. During the process of concentration induced by evaporation, Ca2? was deposited more easily in the form of carbonate owing to its lower solubility than that of magnesium salt in water, which results in the loss of Ca2? in the lake. Therefore, endogenic calcite may be an important feature of sediments in this lake. This was discussed in anther paper (Ju et al. 2009). Vertical variation of physicochemical characteristics of lake water PAR and temperature During the period of field work from 10–22 August 2006, the midday solar radiation reached more than 4000 lmol s-1 m-2 at 10–22 lake surface on a sunny day. Based on the data of site 8 (near XS10) and site 37 (near LW) measured in situ and those of XS10 and LW (Fig. 1), the Z1% (the depth at which the irradiance decreases to 1% of surface intensity) is 22 m for site LW and 33 m for site XS10 (Fig. 7). However, the values of LDO are actually high even in the bottom layer. Therefore, further work should be done to study the euphotic zone of the lake. Thermal stratification is evident in this lake. The metalimnion (20–30 m) separates the surface water of the
123
123
24.8
29.6
29
64.1
65.1
73.4
22.0
22.1
71.6
64.1
67.5
79.8
48.7
60.0
60.5
Minimum
Maximum
Number
River water JQZW1-1
JQZW2-1
JQ1-1
JQH1-1
JQH1-2
KQ1-1
XSW1-1
XSW2-1
XSW3-1
DQBYW11
RDHW1-1
RDHW1-2
(Ca2??Mg2?)/TZ?
16
74.9
32
60.3
36.6
37.1
49.0
16.3
30.6
31.5
20.8
56.4
56.4
22.6
31.0
32.3
29
54.7
49.1
53.2
16
48.5
16.1
25.7
97.0
97.1
97.7
96.2
98.1
95.6
92.4
78.5
78.4
96.0
96.0
96.4
29
81.2
77.1
79.2
HCO3-/TZ-
16
92.3
74.3
86
94.6
94.8
92.7
97.9
95.5
94.4
93.3
93.1
93.3
97.4
93.5
93.3
29
76.7
69.7
72.7
16
75.3
27.3
61.1
Lake sites 1 and 2 refer to the broad lake area and the western alluvial fan of Puma Yum Co, respectively
TZ and TZ stand for total cations and total anions, respectively
-
26
Mean
?
Mg2?/TZ?
SO42-/TZ-
(Na??K?)/TZ?
TDS
5.3
5.1
7.2
2.1
4.5
5.5
6.6
6.8
6.6
2.5
6.4
6.6
29
29.5
22.3
25.9
16
64
23.7
36.8
3.0
2.9
2.0
3.6
1.9
4.0
7.2
21.0
21.1
4.0
3.5
3.1
29
22.6
18.7
20.5
16
25.5
7.7
13.9
174.7
184.6
667.6
121.7
143.3
280.5
270.3
543.3
547.7
54.2
307.2
312.1
29
307.6
266.1
285.6
16
264.4
48.2
127.5
Lake site 1 Lake site 2 Lake site 1 Lake site 2 Lake site 1 Lake site 2 Lake site 1 Lake site 2 Lake site 1 Lake site 2 Lake site 1 Lake site 2 Lake site 1 Lake site 2
Ca2?/TZ?
Table 1 Ionic composition (equiv.%) and TDS (mg l-1) for water samples from Puma Yum Co and inflow rivers
284 Limnology (2010) 11:281–287
Limnology (2010) 11:281–287
285
Fig. 4 Contour maps of pH and LDO
b
5
JQHK
Na
mmol l-1
4
K
3
Mg
2
Ca Cl
1
mmol l-1
a
SO4
0
HCO3
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Na
XSHK
K Mg Ca Cl SO4
1 2 3 4 5 6 7 8 9 10 11 12 13 14
HCO3
d
Cl NO3 SO4 HCO3 2
3
4
5
6
350 300
TDS(mg l-1)
mmol l-1
Ca
Station
c 5 4 3 2 1 0
K Mg
1
Station
Na
RDHK
4.5 4 3.5 3 2.5 2 1.5 1 0.5 0
250
JQHK
200
RDHK
150
XSHK
100 50 0 1 2 3 4 5 6 7 8 9 101 1 121 31 4
Station
Station
Fig. 5 Spatial distribution of the hydro parameters of Puma Yum Co. The X axis is the sampling stations. a–c Show the three survey lines in the lake. d The TDS variation along the three survey lines (see Fig. 1)
28.6
28.55
28.5 90.25
90.3
90.35
90.4
90.45
90.5
Fig. 6 Water ions and total dissolved solids (TDS, in mg l-1)
epilimnion (0–20 m) from the deep water of the hypolimnion ([30 m depth). Hydrogeochemistry The results of two-factor analysis of variance show that, in the central lake area, the pH of water is dependent on both depth and sampling site, i.e., it has both horizontal and vertical
variability. LDO is only sensitive to depth variation, whereas other hydrochemistry parameters, including concentrations of Ca2?, Mg2?, HCO3-, and SpCond, are independent of depth variation (Table 2). Therefore, whether there is a chemical stratification in this lake still remains unclear. The concentration of Ca2? in XSHK10 and LW is around 30 mg l-1 (Fig. 7), which is different from the concentration of 15.6 or 10.2 mg l-1 in the former study (Murakami et al. 2007). Although the two profiles were collected from different parts of the central lake in different years, the data show high coincidence even measured by different instruments. Therefore, we believe our data are better than those of Murakami et al. (2007). Furthermore, at the maximal depth of the two profiles, the concentration of Ca2? seems slightly higher, which is also opposite to the findings of Murakami et al. (2007). The fact that lower pH at the deepest depth area would cause less deposition of Ca2? or more dissolution of CaCO3 (Kelts and Hsu¨ 1978; Dean 1999) may explain this phenomenon.
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Limnology (2010) 11:281–287
Fig. 7 Vertical profiles of lake water parameters in site 8 (near XS10, solid lines) and site 37 (near LW, dashed lines) of water temperature (Temp, °C), pH, photosynthetically active radiation (PAR, lmol s-1 m-2), and concentrations of luminescent dissolved oxygen (LDO, mg l-1) and Ca2? (mg l-1)
Table 2 Two-factor analysis of variance with no re-experiment at 0.01 significance level Parameter
Source
pH
Depth
7.856
10
0.786
5.379
0.000
2.55
Site
5.000
8
0.625
4.279
0.000
2.74
13.824
10
1.382
3.469
0.001
2.55
5.090
8
0.636
1.597
0.139
2.74
43.721
10
4.372
2.444
0.013
2.55
8
102.315
57.201
0.000
2.74
1.912
8
0.239
0.305
0.953
2.59
43.277
2
21.638
27.600
0.000
3.63
LDO
Depth Site
SpCond
Depth Site
Ca2?
Depth Site
HCO3-
Depth
SS
df
818.52
MS
F
P-value
Fcrit
598.782
8
74.848
1.510
0.230
3.89
Site
1177.649
2
588.824
11.876
0.001
6.23
TDS
Depth Site
461.308 4154.922
8 2
57.664 2077.461
1.314 47.343
0.305 0.000
3.89 6.23
Mg2?
Depth
5.779
8
0.722
2.016
0.111
3.89
45.832
2
22.916
63.966
0.000
6.23
Site
Source means the variance source of each parameter, SS sum of squares for depth or site, df degree of freedom, MS mean square F and Fcrit are the calculated Fisher criterion and the table value of the Fisher criterion, respectively P-value denotes the possibility of the truth of the null hypothesis that the parameter is independent of factor (depth or site). If F [ Fcrit (or P-value \ 0.01), the null hypothesis is false, and vice versa
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Conclusions Through the analysis of submarine topography and physicochemical features of Lake Puma Yum Co, we have gained further limnological understanding of this lake. The whole submarine topography reveals that there is a subaquatic alluvial fan in the west part of the lake. Horizontal analysis of the water’s physicochemical features indicates the apparent spatial heterogeneity of physicochemical features on the fan, which is contrasted with the relatively uniformity in other lake areas. Therefore, as the maximal inflow, the Jiaqu River has a great influence on Lake Puma Yum Co. Vertical analysis of water characteristics using two-factor analysis of variance with no re-experiment shows that the temperature, dissolved oxygen, and pH of water vary with water depth rhythmically, whereas ions show no evidently vertical variation, which indicates that the chemical stratification is not obvious in this lake. But this does not exclude slightly higher concentrations of Ca2? induced by lower pH in the bottom of deep lake water. The hydrochemical difference between inflow water and lake water reveals the loss of Ca2? in lake water, which indicates calcite deposition may be an important characteristic of the lake sediment. Acknowledgments This study was supported by the National Natural Science Foundation of China (grant no. 40871099), the National Basic Research Program of China (grant no. 2005CB422002), and the Knowledge Innovation Project of the Chinese Academy of Sciences
287 (grant no. KZCX2-YW-146-4). The authors thank the anonymous reviewer for the constructive remarks and members from both Chinese and Japanese teams for their assistance in the field investigations.
References Bureau of Geology and Mineral Resources of Xizang Autonomous Region (1993) Regional geology of Xizang (Tibet) (1993). Geological Publishing House, Beijing, p 142 (in Chinese) Dean WE (1999) The carbon cycle and biogeochemical dynamics in lake sediments. J Paleolimnol 21:375–393 Guan ZH, Chen CY, Ou YX, Fan YQ, Zhang YS, Chen ZM, Bao SH, Cu YT, He XW, Zhang MT (1984) The rivers and lakes of Tibet. Science Press, Beijing, pp 162–168 (in Chinese) Ju JT, Zhu LP, Wang JB, Xie MP, Zhen XL, Wang Y, Peng P (2009) Water and sediment chemistry of Lake Pumayum Co, South Tibet, China: implications for interpreting sediment carbonate. J Paleolimnol. doi:10.1007/s10933-009-9343-6 Kelts K, Hsu¨ KJ (1978) Freshwater carbonate sedimentation. In: Lerman A (ed) Lakes, chemistry geology physics. Springer, New York, pp 295–321 Mitamura O, Seike Y, Kondo K, Goto N, Anbutsu K, Akatsuka T, Kihira M, Tsering TQ, Nishimura M (2003) First investigation of ultraoligotrophic alpine Lake Puma Yum Co in the preHimalayas, China. Limnology 4:167–175 Murakami T, Terai T, Yoshiyama Y, Tezuka T, Zhu LP, Tetsuya M, Nishimura M (2007) The second investigation of Lake Puma Yum Co located in the Southern Tibetan Plateau, China. Limnology 8:331–335. doi:10.1007/s10201-007-0208-2 Nishimura M, Takada M (2003) Report on scientific research expedition to Lake Puma Yum Co on the Tibetan Plateau, 2001 (in Japanese with English abstract). Tokai University Himalayan Expedition Committee, Hiratsuka
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