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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, F01011, doi:10.1029/2006JF000493, 2007
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Water chemistry of the Zhujiang (Pearl River):
Natural processes and anthropogenic influences
Shu-Rong Zhang,1 Xi Xi Lu,1 David Laurence Higgitt,1 Chen-Tung Arthur Chen,2
Hui-Guo Sun,3 and Jing-Tai Han3
Received 2 March 2006; revised 6 September 2006; accepted 18 September 2006; published 22 March 2007.
[1] The temporal and spatial variations of major ions in the Zhujiang (Pearl River)
were analyzed using long-term water chemistry data of major dissolved ions (Ca2+, Mg2+,
2
the sum of Na+ and K+, HCO
3 , SO4 , Cl ) and dissolved silica (SiO2) from
75 hydrological stations (1958–2002). The total dissolved solids (TDS) within the
Zhujiang basin varies from 34.0 mg/l to 416.1 mg/l generally decreasing from upstream
to downstream along the main stem of the Zhujiang. Rock weathering is the dominant
controlling factor for the water chemistry of the Zhujiang, and more specifically, on
average, 68% (22–92%) of total dissolved load comes from carbonate weathering,
22% (2–68%) from silicate weathering, and 10% (3–24%) from evaporite weathering,
respectively. The flux calculations indicate that in total about 41.8 106 tonnes/year of
TDS are transported out of the Zhujiang (excluding the Delta Region), averaged for
the period 1958–2002. Changes in water chemistry can be observed from long-term trend
analysis, notably for SO2
4 and Cl , as a result of anthropogenic influences, such as acid
deposition, domestic and industrial wastewater discharge, and basin water resource
development. An intense reforestation policy coupled with rapid reservoir development in
the Zhujiang Basin would trigger more significant anthropogenic impacts on water
chemistry in the future.
Citation: Zhang, S.-R., X. X. Lu, D. L. Higgitt, C.-T. A. Chen, H.-G. Sun, and J.-T. Han (2007), Water chemistry of the Zhujiang
(Pearl River): Natural processes and anthropogenic influences, J. Geophys. Res., 112, F01011, doi:10.1029/2006JF000493.
1. Introduction
[2] Following the pioneering efforts in collating and updating river geochemistry databases [Clarke, 1916; Livingstone,
1963; Degens, 1989], studies of dissolved major ions in
river waters have been carried out in more systematic and
holistic approaches. The most notable cases include the
Amazon [Richey et al., 1991; Stallard and Edmond, 1981,
1983, 1987], the Orinoco [Vegas-Vilarrubia and Paolini,
1985; Edmond et al., 1996], the Ganges-Brahmaputra
[Sarin and Krishnaswami, 1984; Sarin et al., 1989; Galy
and France-Lanord, 1999], and the Congo [Nkounkou and
Probst, 1987; Probst et al., 1992]. These extensive studies
not only reported the signatures of river systems responding
to natural processes, such as atmosphere precipitation and
chemical weathering, but also detected the significant
signatures responding to human activities. The most striking
impacts from human activities have been summarized by
Meybeck [2003] as eight ‘‘syndromes’’: flow regulation,
1
Department of Geography, National University of Singapore,
Singapore.
2
Institute of Marine Geology and Chemistry, National Sun Yat-Sen
University, Kaohsiung, Taiwan.
3
Institute of Geology and Geophysics, Chinese Academy of Sciences,
Beijing, China.
Copyright 2007 by the American Geophysical Union.
0148-0227/07/2006JF000493$09.00
fragmentation of river course, sediment imbalance, neoarheism (dry-up of rivers), chemical contamination, acidification, eutrophication and microbial contamination. Many
rivers have clearly become more controlled by anthropogenic influences than by natural processes [Turner et al.,
1990; Meybeck, 2003; Xu, 2004; Lu, 2004], such as the
Seine [Meybeck, 1998], the Colorado [Schwartz et al.,
1990], the Huanghe [Chen et al., 2005], the Yangtze [Lu
and Higgitt, 1998; Chen et al., 2001], and the Mekong [Lu
and Siew, 2006].
[3] Since the first report detailing major ion chemistry of
large Chinese rivers in the international literature [Hu et al.,
1982], several river biogeochemistry studies have been
initiated, especially concerning the Changjiang (Yangtze
River) and Huanghe (Yellow River) [e.g., Gan, 1985; Zhang
et al., 1990, 1995a; Chen et al., 2002, 2005]. It has been
found that with increasing population pressure and rapid
economic development, the two longest rivers in China have
been significantly impacted by some of the syndromes
identified by Meybeck [2003], including industrial sulfide
pollution [Chen et al., 2002] as well as water diversion,
damming and farmland irrigation [Chen et al., 2005]. However, fewer studies about water chemistry of the Zhujiang
(Pearl River) have been reported in the public domain. Chen
and He [1999] briefly reported the general characteristics of
the Zhujiang water chemistry averaged for the period of
1954– 1984, but included no detailed analysis about distribution variability, fluxes or inferred processes, including
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ZHANG ET AL.: WATER CHEMISTRY OF THE ZHUJIANG
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Figure 1. The Zhujiang (Pearl River) Basin and the location of sampling stations. The thick lines
represent the main channel of the three main rivers in the Zhujiang Basin, the Xijiang, Beijiang and
Dongjiang, and the thin lines represent the tributaries. The solid circles represent the main channel
stations (the Xijiang: 1. Zhanyi; 2. Xiqiao; 3. Gaoguma; 4. Xiaolongtan; 5. Jiangbianjie; 6. Bajie;
7. Longtan; 8. Du’an; 9. Qianjiang; 10. Wuxuan; 11. Dahuangjiangkou; 12. Wuzhou; 13. Gaoyao; the
Beijiang: 68. Shijiao; the Dongjiang: 73. Boluo) and the open circles represent the tributary stations. The
shadowed areas indicate the distribution of carbonate rocks in the basin.
anthropogenic influences. In the present study, the major
2
dissolved ions (Ca2+, Mg2+, Na+ + K+, HCO
3 , SO4 , Cl ),
and dissolved silica (SiO2) at 75 hydrological stations in the
Zhujiang for the period of 1958 – 2002, have been intensively interrogated. On the basis of this database, the spatial
and temporal variations of major ions and dissolved silica
were analyzed. Furthermore, the major mechanisms controlling the water chemistry of the Zhujiang were explored,
and the signals of anthropogenic influence determined on
the basis of changes in the long-term trends.
2. Study Area and Methods
2.1. Zhujiang (Pearl River) Basin
[4] The Zhujiang (Pearl River) is the second largest
Chinese river in terms of annual water discharge (336 km3
[Pearl River Water Resources Committee (PRWRC), 1991]),
which is less than the Changjiang (899 km3) [Chen et al.,
2002] but much higher than the Huanghe (36.6 km3) [Chen
et al., 2005]. The runoff from the Zhujiang is one of the
most important contributors of dissolved materials and
sediment to South China Sea (SCS). The Zhujiang Basin
is situated between 21.31° – 26.49° N and 102.14° –
115.53° E with a drainage area of 0.45 106 km2.
Generally, the elevation in the basin decreases from northwest (Yunnan-Guizhou Plateau) to southeast (the Zhujiang
(Pearl River) Delta). It covers a region of subtropical to
tropical monsoon climate straddling the Tropic of Cancer.
The mean annual temperature across the basin ranges from
14 to 22°C and the mean annual precipitation ranges from
1200 to 2200 mm. Seasonal runoff is unevenly distributed,
with about 80% of annual runoff between April and
September (the ‘‘flood season’’) and more than 50% between July and September.
[5] The Zhujiang water system includes three principal
rivers: the Xijiang, Beijiang, and Dongjiang, and some
small rivers draining the Zhujiang (Pearl River) Delta
(Figure 1). The Xijiang River, is the main stem of the
Zhujiang, covering 77.8% of the drainage basin area, and
providing 63.9% of the water discharge. The main channel
of the Xijiang originates in the Maxiong Mountain of
Yunnan Province in southwest China, and flows southeastward through Guizhou, Guangxi and Guangdong Provinces,
to enter the SCS through the Pearl River Delta in
Guangdong Province. The total length is 2214 km. The
main channel of the Xijiang, like many Chinese rivers, has
distinctive names for particular sections: Nanpanjiang,
Hongshuihe, Qianjiang, Xunjiang, and Xijiang (moving in
a downstream direction). The five principal tributaries of the
Xijiang (in the downstream direction) are the Beibanjiang,
Liujiang, Yujiang, Guijiang, and Hejiang. Both the Beijiang
and Dongjiang originate in Jiangxi Province and flow south
through Guangdong Province. All the Xijiang, Beijiang and
Dongjiang waters flow to the Zhujiang (Pearl River) Delta
and empty through eight large distributaries into the SCS.
[6] Geologically, the Zhujiang Basin consists of various
source rocks from Precambrian metamorphic rocks to
Quaternary fluvial sediments. Carbonates are widely distributed in the Zhujiang Basin, accounting for 39% of the
total basin area [PRWRC, 1991]. In the headwaters of the
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ZHANG ET AL.: WATER CHEMISTRY OF THE ZHUJIANG
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Table 1. Major Ion Concentrations of the Zhujianga
Number
Station name
pH
Ca2+
Mg2+
Na+ + K+
Cl
SO2
4
HCO
3
Total Dissolved
Solids
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
Zhanyi
Xiqiao
Gaoguma
Xiaolongtan
Jiangbianjie
Bajie
Longtan
Du’an
Qianjiang
Wuxuan
Dahuangjiangkou
Wuzhou
Gaoyao
Dadukou
Zhedong
Xishan
Nanqiao
Yuguopu
Youjiazhai
Tagu
Hebian
Maling
Xinqiao
Rongfeng
Caopingtou
Gaoche
Huishui
Pingla
Fengshan
Chouyu
Baben
Shihuichang
Yongwei
Chang’an
Liuzhou
Leihuang
Guyi
Xiaochuang’an
Libo
Jinchengjiang
Sancha
Huangmian
Duiting
Darongjiang
Baise
Xiayan
Xiyangjie
Funing
Wuming
Nanning
Guixian
Longzhou
Laiduan
Ningming
Na’an
Guilin
Pingle
Shaoping
Lipu
Gongcheng
Xindu
Gulan
Guanliang
Taiping
Rongxian
Jinji
Guiwang
Shijiao
Zhenwan
Huanggang
Lianzhouping
Shigou
8.2
8.1
8.1
8.3
8.0
7.8
45.5
51.4
51.7
53.8
61.0
41.4
45.1
44.9
42.4
36.3
38.4
31.0
29.7
39.8
40.6
47.0
65.2
43.5
60.8
50.9
45.0
44.0
63.8
32.7
44.5
49.1
53.1
28.1
39.9
27.7
30.9
11.3
11.5
6.4
21.1
5.3
5.0
20.6
39.2
48.3
44.4
18.5
19.9
9.2
35.8
42.8
47.1
48.7
34.5
41.3
37.2
35.6
35.9
7.5
33.4
25.1
33.2
24.6
32.3
31.3
18.8
17.8
11.3
9.0
8.2
9.8
3.3
23.1
10.1
19.9
30.2
7.8
14.4
8.5
17.6
15.2
14.6
16.0
7.6
6.9
9.8
7.0
5.7
4.1
5.0
9.1
12.5
13.2
15.6
9.9
10.1
8.2
7.0
11.2
20.3
7.8
14.7
17.2
10.6
10.0
4.7
7.3
6.7
2.6
2.0
2.0
3.9
1.1
1.7
5.8
8.1
5.3
7.3
2.6
3.8
2.4
4.0
4.0
8.0
7.1
5.3
3.6
4.0
3.1
3.3
1.8
7.2
2.2
5.5
5.8
3.6
4.5
2.7
3.2
2.5
2.2
2.4
3.0
1.3
2.7
1.8
2.4
4.8
2.4
17.2
7.3
6.6
5.1
5.3
13.8
2.0
3.6
4.4
3.2
5.1
2.2
8.6
13.6
9.6
6.3
7.7
1.7
1.7
5.1
6.9
11.6
15.4
8.9
9.8
8.0
3.0
13.8
14.7
19.8
3.7
4.8
12.4
4.5
3.7
2.2
3.8
6.9
3.3
3.7
5.4
2.4
3.8
3.0
6.8
6.4
2.9
2.8
21.9
5.7
5.1
4.0
5.8
12.0
19.0
4.0
2.9
21.6
3.7
4.1
3.6
5.9
7.0
14.9
5.0
24.5
7.8
7.6
8.5
4.4
11.7
15.6
8.1
3.9
7.0
3.6
3.0
3.7
3.1
4.2
2.6
2.7
3.9
1.7
3.3
2.8
3.5
4.9
5.2
7.7
1.2
0.7
0.8
4.2
0.8
3.0
4.2
2.5
1.0
0.3
0.6
1.8
0.9
0.5
1.1
2.8
2.3
0.7
1.3
0.5
0.6
3.6
3.2
2.6
2.9
1.5
1.7
2.0
1.1
1.6
1.6
2.0
4.8
1.4
1.9
1.4
0.9
3.9
3.5
0.8
1.5
2.7
1.6
1.7
2.7
1.5
3.8
2.2
1.3
1.9
2.6
0.8
1.4
4.3
8.5
10.1
26.2
16.4
19.2
22.1
4.5
3.6
11.6
9.5
8.7
5.4
10.4
27.4
29.3
12.7
19.1
11.6
13.3
10.1
8.0
28.3
42.5
12.0
37.3
52.3
26.3
14.2
15.0
27.9
10.6
2.0
17.3
5.4
6.5
3.0
6.4
13.5
10.0
3.7
14.9
1.7
4.2
4.5
3.1
3.7
4.9
6.5
25.2
3.1
4.0
2.7
3.0
15.7
11.1
6.9
6.6
33.2
3.7
5.5
2.4
4.5
6.3
13.0
2.0
31.6
5.3
9.4
5.1
3.7
5.9
10.3
208.3
184.0
214.2
207.3
236.2
192.6
161.4
165.1
163.5
134.3
140.6
108.5
118.3
157.2
155.3
187.3
243.5
149.6
215.9
178.2
156.2
164.2
273.3
114.3
173.1
175.0
186.3
144.3
157.5
130.0
118.7
54.1
44.7
32.0
80.4
21.8
25.4
91.0
150.6
168.1
157.8
67.5
77.9
39.6
141.0
152.4
181.0
173.9
144.0
145.5
131.4
124.1
130.9
39.3
166.5
80.6
114.1
112.3
106.3
117.2
72.9
79.0
50.8
54.0
41.2
62.0
30.5
87.1
49.7
78.5
134.9
53.5
301.9
266.4
323.8
309.7
340.2
293.8
223.7
228.2
236.5
189.9
196.0
152.9
176.5
249.2
255.0
277.7
364.2
224.0
303.0
253.2
223.8
263.5
416.1
178.8
285.7
310.0
280.1
210.8
232.3
214.5
171.5
80.7
88.8
50.6
116.4
34.0
43.6
138.3
211.8
232.6
233.2
95.3
112.5
60.2
197.8
212.6
245.0
240.7
232.4
206.0
186.4
170.9
181.4
77.7
238.1
122.9
162.5
198.4
151.0
165.3
102.1
112.1
80.6
94.7
62.7
133.1
49.4
131.9
77.8
109.7
188.9
93.8
8.1
8.0
7.9
7.4
7.9
7.6
8.3
8.3
7.9
8.2
8.0
8.2
7.8
7.8
8.4
7.8
7.7
8.1
7.8
7.9
7.2
7.7
7.4
7.9
7.6
7.9
7.7
7.1
7.5
8.1
8.0
7.9
8.2
7.6
7.3
7.9
7.5
8.1
7.8
7.7
7.5
7.5
7.4
7.5
6.9
7.4
7.4
7.6
7.9
7.5
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SiO2
5.4
3.3
12.6
7.6
9.2
4.2
5.9
5.5
6.1
7.5
5.1
5.5
5.3
10.7
12.0
4.2
7.5
5.3
13.3
5.4
1.0
4.4
4.0
6.1
7.9
6.5
6.2
9.4
4.1
5.1
5.3
5.6
5.3
5.4
11.0
10.2
8.2
11.5
9.4
5.5
11.6
8.1
4.8
4.5
4.0
7.7
5.0
6.6
6.2
5.2
ZHANG ET AL.: WATER CHEMISTRY OF THE ZHUJIANG
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Table 1. (continued)
Number
73
74
75
Station name
Boluo
Longchuan
Heyuan
pH
Ca2+
Mg2+
7.0
7.3
7.3
5.6
6.4
5.7
1.6
2.8
1.7
Na+ + K+
Cl
SO2
4
HCO
3
6.8
13.6
5.8
2.8
1.2
0.5
3.9
9.4
2.4
31.8
52.9
35.4
Total Dissolved
Solids
52.7
86.3
51.5
SiO2
13.4
a
Units are mg/l. Average is for the period 1958 – 2002.
Xijiang, spectacular karst topography is well developed,
such as stone forest in Guizhou and eastern Yunnan, and the
tower karst of Guangxi Province. The igneous rocks are
dominated by granites with acid to intermediate composition, covering about half of the area of Guangdong Province. Minor evaporites are mainly scattered in the upper
reaches of the Zhujiang. Pyrites can be found concomitant
with high sulfur content coal in Yunnan and Guizhou
provinces. Quaternary fluvial sediments are mostly developed in the lower alluvial plain, the delta plain and the
interior river valley plain of Guangdong and Guangxi
provinces.
2.2. Data Sources
[7] For the present study, data on major ions and dissolved silica measured at 75 hydrological stations in the
Zhujiang Basin over the period of 1958 – 2002 were
extracted from the Hydrological Yearbooks of the People’s
Republic of China (Table 1 and Figure 1). Most stations
have been sampled monthly or more frequently for periods
exceeding 10 years. However, for most stations in the
Xijiang and the Beijiang, water chemistry mointoring was
suspended from 1969 to 1978 during the Cultural Revolution. Sixty-seven stations in the Xijiang (13 along the main
channel), five stations in the Beijiang, and three stations in
the Dongjiang were included in the study, while stations in
the Pearl River Delta itself were excluded because of the
complex tidal effects and dense river networks in the delta
region.
[8] The analyses of major ions and dissolved silica were
conducted in the laboratories under the authority of PRWRC
using regular methods as described by Chen et al. [2002,
2005]. After filtrating the raw water samples through a
0.45-mm membrane, Ca2+ and Mg2+ were analyzed by
EDTA titration, Na+ and K+ by difference using the ionic
balance or by flame spectrometry, HCO
3 by acid titration,
SO2
4 by BaCl2 titration, Cl by AgNO3 titration, and SiO2
by the molybdenum blue method. The total dissolved solids
(TDS) were determined by drying the filtrate at 180°C for
1 hour and measuring the weight loss. The pH of some
samples was also measured using a glass electrode pH meter.
[9] The quality of the water chemistry data in the Zhujiang Basin can be verified by comparsion with monitoring
by the United Nations Global Environment Monitoring
System (GEMS)/Water Program. This comparison has been
used in other Chinese river studies as a means of data
quality control [Chen et al., 2002, 2005]. The most downstream station of the Xijiang, station Gaoyao, has been
monitored under the GEMS/Water Program since 1980
(available at http://www.gemswater.org/publications/index-e.
html). A comparison of the major element concentration data
for the period of 1991–1993 indicates that the data set from
the Hydrological Yearbooks is in a good agreement with the
data set monitored by the GEMS/Water program (Table 2).
2.3. Statistical Analysis
[10] The modified seasonal Mann-Kendall test was
employed in this study to examine the long-term trend of
major ion concentrations due to its robustness against
seasonality, departure from normality, missing values, and
serial correlation [Hirsch et al., 1982; Hirsch and Slack,
1984]. Trends were considered as statisitically signicant
when r < 0.01. If a trend was detected, the trend magnitude
was estimated by the seasonal Kendall slope estimator, which
is the median of slopes of all pairs of data over years for each
month [Hirsch et al., 1982]. For stations where multiple
samples were taken within one month, only the sample near
midmonth was used to examine the long-term trend.
3. Hydrological Characteristics
[11] Figure 2 shows the seasonal variation of water
discharge at the three downstream stations of the Xijiang,
Beijiang and Dongjiang, respectively: stations Gaoyao,
Shijiao, and Boluo. There is a obvious distinction of dry
season and wet season within each year for every station,
with the largest water discharge in June (Beijiang and
Dongjiang) or July (Xijiang) and the smallest water discharge in January. The ratios of maximum to minimum
monthly mean discharge averaged for the period of 1958–
2002 are 7.6, 4.8 and 4.1 at stations Gaoyao, Shijiao, and
Buoluo, respectively. However, the maximum monthly
mean discharge was as high as 30 to 40 times the minimum
monthly mean discharge for some years in the 1960s.
[12] Figure 2 also indicates extremely large standard
deviations in monthly mean discharges for the period of
Table 2. Major Ion Concentrations of the Zhujiang at Station Gaoyao for the Period of 1991 – 1993: A Comparison With GEMS Water
Programme (Arithmetric Mean ± Standard Deviation)
Sources
Discharge,
m3/s
pH
Cond,
ms/cm
Ca2+,
mg/l
Mg2+,
mg/l
Na+,
mg/l
K+,
mg/l
Cl,
mg/l
SO2
4 ,
mg/l
HCO
3,
mg/l
This study
GEMS/water programme
6502 ± 6773
6606 ± 6939
7.9 ± 0.2
7.9 ± 0.2
239 ± 39
224 ± 29
32.6 ± 5.2
32.9 ± 4.0
5.4 ± 1.5
5.0 ± 1.0
(4.4 ± 1.9)a
3.0 ± 1.0
1.2 ± 0.2
2.2 ± 0.8
3.0 ± 0
10.3 ± 2.8
11.0 ± 2.0
117 ± 18
105 ± 10
a
Sum of Na+ and K+.
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ZHANG ET AL.: WATER CHEMISTRY OF THE ZHUJIANG
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for the period of 1958 – 1973 to 5.2 averaged for the period
of 1974 – 2002, the long-term change trend cannot be
detected.
4. Major Ion Chemistry
4.1. Spatial Variation
[13] Table 3 shows the major dissolved element data
averaged over the period of 1958 – 2002 at 13 stations
in the main channel of the Xijiang, together with the most
downstream stations of the main tributaries of the Xijiang
as well as the most downstream stations of the Beijiang
and Dongjiang. The TDS concentration of the Zhujiang
ranges from 34.0 mg/l to 416.1 mg/l, with a median of
189.9 mg/l (Figure 4), more than twice the global median
of 65 mg/l [Meybeck and Helmer, 1989]. TDS concentra-
Figure 2. Monthly variation of water discharge of the
Zhujiang (average for the period of 1958– 2002) at station
Gaoyao (number 13), Shijiao (number 68) and Boluo
(number 73), which are the most downstream stations of
Xijiang, Beijiang and Dongjiang, respectively.
1958 – 2002, which can be more clearly shown by long-term
series of monthly mean discharge (Figure 3). However, the
fluctuations of water discharge at three stations did not
show any significant change trend during the study period
(Figures 3a, 3b, and 3c). Even when the intrayear distribution of water discharge was significantly changed at station
Boluo (Figure 3d), where the ratio of maximum to minimum monthly mean discharge shifted from 12.2 averaged
Figure 3. Long-term variations of water discharge at the
most downstream stations of Xijiang, Beijiang, and
Dongjiang. (a) Gaoyao, (b) Shijiao, (c) Boluo, and (d) the
ratio of maximum/minimum monthly mean discharge at
station Boluo.
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Table 3. Average Concentrations of Major Dissolved Ions of the Zhujiang
Ca2+,
mg/l
Mg2+,
mg/l
River/ Tributary
Station Name
Area, km2
pH
Nanpanjiang
Zhanyi
Xiqiao
Gaoguma
Xiaolongtan
Jiangbianjie
Bajie
Longtan
Du’an
Qianjiang
Wuxuan
Dahuangjiangkou
Wuzhou
Gaoyao
574
3194
6198
15405
24624
46845
105830
119245
128165
196255
290760
329705
351535
8.2
8.1
8.1
8.3
8.0
7.8
Zhedong
Liuzhou
Guixian
Shaoping
Gulan
20372
45785
89235
14965
8273
7.6
7.9
7.6
7.8
7.5
Major
40.6
21.1
37.2
24.6
17.8
Shijiao
38363
7.4
23.1
2.7
Boluo
25325
7.0
5.6
1.6
Hongshuihe
Qianjiang
Xunjiang
Xijiang
Beipanjiang
Liujiang
Yujiang
Guijiang
Hejiang
Beijiang River
8.1
8.0
7.9
7.4
Na+ + K+,
mg/l
Cl mg/l
SO2
4 ,
mg/l
8.1
3.9
7.0
3.6
3.0
3.7
3.1
4.2
2.6
2.7
3.9
1.7
3.3
8.5
10.1
26.2
16.4
19.2
22.1
4.5
3.6
11.6
9.5
8.7
5.4
10.4
3.5
2.3
4.8
0.8
1.7
7.6
6.8
Xijiang Main Channel (Sections)
45.5
14.4
17.2
51.4
8.5
7.3
51.7
17.6
6.6
53.8
15.2
5.1
61.0
14.6
5.3
41.4
16.0
13.8
45.1
7.6
2.0
44.9
6.9
3.6
42.4
9.8
4.4
36.3
7.0
3.2
38.4
5.7
5.1
31.0
4.1
2.2
29.7
5.0
8.6
Tributaries of Xijiang
12.5
9.6
3.9
3.7
4.0
5.1
5.8
21.6
3.2
5.9
HCO
3,
mg/l
Total Dissolved
Solids, mg/l
SiO2,
mg/l
208.3
184.0
214.2
207.3
236.2
192.6
161.4
165.1
163.5
134.3
140.6
108.5
118.3
301.9
266.4
323.8
309.7
340.2
293.8
223.7
228.2
236.5
189.9
196.0
152.9
176.5
5.4
3.3
12.6
7.6
9.2
4.2
5.9
5.5
6.1
7.5
5.1
5.5
29.3
6.5
4.0
33.2
4.5
155.3
80.4
131.4
112.3
79.0
255.0
116.4
186.4
198.4
112.1
5.3
6.5
5.5
1.9
9.4
87.1
131.9
2.8
3.9
31.8
52.7
Dongjiang River
tion shows a decreasing trend in the downstream direction
along the main channel of the Xijiang (Table 3 and Figure 4).
The upstream rivers, Nanpanjiang and Beipanjiang have the
higher TDS concentrations (generally larger than 250 mg/l).
Among the major tributaries of Xijiang, Liujiang river and
Hejiang river have lower TDS concentrations, less than
2+
show similar spatial
150 mg/l. In Figure 4, HCO
3 and Ca
patterns to TDS across the whole basin. Using the available
SiO2 data from 50 stations, higher SiO2 generally occurs at
2+
the stations with lower TDS, HCO
3 and Ca . Most of the
2
+
extreme values for SO4 , Cl and Na + K+ are found at
the stations in the upstream rivers, expecially Nanpanjiang
and Beipanjiang.
[14] Comparing the Xijiang, Beijiang, and Dongjiang,
TDS shows a general decreasing trend from the Xijiang,
Beijiang to Dongjiang. There are large varations between
the Xijiang, Beijiang, and Dongjiang in terms of the
proportion of major cations and major anions in equvalent
2+
account for
units respectively (Table 4). HCO
3 and Ca
85.6% of the total anions and 64.3% of the total cations,
respectively, averaged in equvalent units in the Xijiang
subbasin, which is characteristic of a typical carbonate river,
such as the Changjiang, Seine and Mackenzie. The major
cations can be ranked in terms of proportions as follows:
Ca2+ > Mg2+ > Na+ + K+ and the major anions as: HCO
3 >
SO2
4 > Cl . In the Beijiang and Dongjiang subbasins, the
2+
are lower, especially in the
proportions of HCO
3 and Ca
Dongjiang subbasin, where the proportions of HCO
3 and
Ca2+ are 81.8% and 38.2%, respectively. Similarly, TDS
decreased and the proportions of Na+ + K+ increased from
the Xijiang, Beijiang, to Dongjiang.
[15] Piper diagrams, also known as trilinear diagrams
[Piper, 1944] were employed to illustrate the dominant
types of water chemistry (Figure 5). The proportions (in
equivalents) of the major cations (Ca2+, Mg2+, and the sum
of Na+ and K+) were plotted in Figure 5a, the proportions
2
(in equivalents) of the major anions (HCO
3 , SO4 , and
Cl ) in Figure 5b and the proportions (in equivalents) of
2
HCO
3 , the sum of SO4 and Cl , and SiO2 (on the basis of
50 stations where SiO2 data are available) in Figure 5c.
Stations cluster toward the Ca2+ apex (most with a proportion of Ca2+ larger than 60.0%) in Figure 5a, toward the
HCO
3 apex (ranging from 72.6% to 95.3%) in Figure 5b,
and also toward the HCO
3 apex in Figure 5c when SiO2
data are included (most stations with a proportion of HCO
3
larger than 70%). The three stations of the Dongjiang
subbasin with smaller TDS concentrations (less than
100 mg/l) have lower proportions of Ca2+ (Figure 5a) and
HCO
3 (Figure 5b), but higher proportions of the sum of
Na+ and K+ (Figure 5a), Cl(Figure 5b), and SiO2 (Figure 5c).
These are typical characteristics of river water controlled by
silicate weathering. The distribution patterns suggest that
the water chemistry of the Zhujiang is dominated by
intensive carbonate weathering in the drainage basin (the
Xijiang and Beijiang basins), with the rivers draining
carbonate regions having higher TDS concentrations than
the rivers draining silicate regions, where TDS are normally
less than 100 mg/l.
4.2. Seasonal Variation
[16] Figure 6 shows the seasonal variations of dissolved
major element concentrations at three main downstream
stations. The concentrations of major elements and TDS
vary slightly during a year, and the ratios of the highest
concentration to the lowest concentration for major elements and TDS are mostly less than 2, except for the ratios
of Cl and Na+ + K+. This is similar to Changjiang [Chen et
al., 2002] and most Himalayan rivers [Galy and FranceLanord, 1999], but different from the Amazon [Gibbs,
1972] and Lena [Gordeev and Sidorov, 1993], where dis-
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Figure 4. Spatial distributions of total dissolved solids (TDS), major ions, and dissolved silica in the
Zhujiang Basin (using ‘‘natural breaks’’ classification scheme in ArcMap for mapping data).
solved solids concentrations decrease significantly in the
flood season because of dilution. The slight decrease of
dissolved solid concentration compared to the drastic increase of discharge suggests that there must be additional
solute sources from drainage basins during the flood season.
One possible source of increasing dissolved solids in the
Zhujiang is the accelerated chemical weathering of rocks
during high flow. Ca2+ and HCO
3 , which are the typical
products of chemical weathering, have the smallest ratios of
maximum to minimum concentration (less than 1.5) among
cations and anions, respectively.
[17] Using monthly (or more frequent) records for the
period 1958 to 2002, the relationships between all dissolved
constituents and water discharge were investigated at the
most downstream stations of the Xijiang, Beijiang and
Dongjiang. The dilution effects of major ions caused by
increasing water flow in the flood season can be expressed
by following log linear equation, the standard rating relationship [Walling and Webb, 1986]:
7 of 17
C ¼ aQb
ð1Þ
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Table 4. Percentage Proportions of Major Cations and Major
Anions in Equivalent Units Averaged in the Xijiang Basin,
Beijiang Basin, and Dongjiang Basin
Cations
Anions
Total
Ca2+, Mg2+, Na+ + Cl, SO42, HCO3, Dissolved
Water System %
Solids, mg/l
% K+, % %
%
%
Xijiang
Bejiang
Dongjiang
64.3
57.7
38.2
21.4
15.4
20.8
14.2
26.9
41.1
3.4
4.8
5.7
11.0
10.1
12.5
85.6
85.0
81.8
195.15
120.45
63.53
where C is the concentration (mg/l) of major constituents or
TDS, Q is water discharge (m3/s), a is the regression
constant and b is the regression exponent, which has a
negative value for each dissolved component as well as
TDS in this study. Although slight, there is a statistically
significant decreasing trend (p < 0.05) of TDS and most of
the major ions with increasing water discharge at the three
stations (Figure 7 and Table 5). The values of b lie in the
range of 0 1, mostly close to 0, which is similar to
results from the Changjiang [Chen et al., 2002], but
markedly different from reported results from some rivers,
where b is generally very close to 1 (e.g., the Congo
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[Probst et al., 1992], the Humber rivers [Jarvie et al., 1997],
and the Seine river [Roy et al., 1999]). There is some
variation in dilution effects between the three stations.
Generally, b values for most dissolved components (except
Cl and SO2
4 ) show decreasing trends following the
sequence: Gaoyao, Shijiao, and Buluo. This indicates
increasing dilution effects following the same sequence.
The difference of slope b for individual dissolved
components at different stations reflects the different
sources and the soluablity of source materials. On the one
hand, the Xijiang (station Gaoyao) and Beijiang (station
Shijiao) have much higher sediment yield than the
Dongjiang (station Boluo), which simultaneously contributes much more dissolved solids during the high-flow
period. On the other hand, the dominant rock types in the
Xijiang and Beijiang subbasins are carbonates, which are
more soluble than aluminosilicates, the dominant rock type
in the Dongjiang subbasin.
4.3. Long-Term Variation
[18] Historical records of water chemistry at most hydrological stations of the Zhujiang extend more than 10 years,
which permits medium- to long-term analysis of water
chemistry. Long-term variations of major ions and TDS at
stations Gaoyao, Shijiao, and Boluo are illustrated in
Figure 5. Piper diagrams showing the relevant dominance (in equivalents) of (a) major cations (Ca2+,
Mg2+, and Na+ + K+), (b) major anions (HCO3, SO42, and Cl), and (c) the relevant dominance of
HCO3, SO42 + Cl, and SiO2 based on 50 stations where SiO2 data is available.
8 of 17
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Figure 6. Seasonal variations of dissolved major element concentrations at three main downstream
stations: (a) Gaoyao, (b) Shijiao, and (c) Boluo.
Figure 8. Seasonal Kendall analysis enables slightly decreasing trends of Na+ + K+, Cl, and TDS at station
Gaoyao (Figure 8a), decreasing trends of Na+ + K +
at station Shijiao (Figure 8b), and decreasing trends of
Na+ + K+, HCO
3 and TDS and an increasing trend of
Cl at station Boluo to be detected (Figure 8c).
5. Chemical Weathering
[19] The first-order mechanisms controlling water chemistry of the world water can be defined as atmosphere precipitation, rock weathering and the evaporation-crystallization
process [Gibbs, 1970; Berner and Berner, 1996]. The
simplest way to judge the controlling mechanisms is to plot
the TDS versus the weight ratio of Na+/(Na++Ca2+) or the
weight ratio of Cl/(Cl + HCO
3 ) [Gibbs, 1970]. The very
low ratios of Cl/(Cl + HCO
3 ) (<0.1) and moderate TDS
concentrations (<500 mg/l) in the Zhujiang waters suggest
that the Zhujiang is a typical river dominated by rock
weathering, according to Gibbs [1970].
[20] Having demonstrated that rock weathering is the
major mechanism controlling the water chemistry of the
Zhujiang, the more specific rock weathering types and
sources of solutes can be investigated further both qualitatively and quantitatively. Before discussing the contributions from three major rock weathering, the contributions
from cyclic salts in the Zhujiang were examined. It is well
known that for rivers dominantly affected by sea salts, such
as the Amazon Basin rivers [Stallard and Edmond, 1981]
and some small coastal rivers [Kennedy and Malcolm, 1977;
Yuretich et al., 1981], that Cl, the most useful reference for
cyclic input to river water, shows a generally decreasing
trend with increasing distance from the the sea. From
Figure 9, it can be seen that chloride in the Zhujiang does
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Figure 7. Plots of the relationship between major ions and
water discharge in logarithmic scales at (a) Gaoyao,
(b) Shijiao, and (c) Boluo (only ions statistically significant
at the significance level of 0.05 in Table 5 were plotted).
not decline with increasing distance from the sea. Chloride
concentration in the Zhujiang is between 0.3 and 8.1mg/l,
with higher concentrations farther inland rather than in the
seashore stations, which suggests other sources of Cl
dominate rather than cyclic salts, such as weathering of
evaporite rocks and anthropogenic pollution. The error
produced by not considering impacts of cyclic salts can
be examined through assuming that all the chloride in the
rivers is from cyclic salt. In this analysis, the lowest Cl
concentration (0.3mg/l) was taken as the cyclic input, and
the proportioned values from other elements were subtracted on the basis of the known element ratios of the
seawater [Berner and Berner, 1987]. The atmospheric
correction makes little difference to most ions (less than
12% to Na+, and less than 2% to Ca2+, Mg2+, K+, and
SO2
4 ). Hence cyclic inputs were not corrected in this study.
[21] Stoichiometric analysis would provide some qualitative information for tracing sources of major dissolved ions
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in weathering-dominated river waters [Stallard and
Edmond, 1983; Zhang et al., 1995b]. The plot of the sum
of Na+ and K+ versus Cl (Figure 10a) indicates the
realtively minor significance of chloride evaporite sources
in the Zhujiang Basin. Most samples deviate above the 1:1
trend line characterizing a pure evaporite source, suggesting
important sources of Na+ and K+ from sodium and potassium aluminosilicates weathering or other anthropogenic
sources rather than chloride evaporite weathering. The plot
of (Ca2+ + Mg2+) versus SO2
4 (Figure 10b) indicate there
are important sources of Ca2+ and Mg2+ from carbonate or
silicate weathering besides evaporite weathering. Most
samples disperse above the 1:1 trend line characterizing
pure sulfate evaporite dissolution. The plot of (Ca2+ +
Mg 2+ ) versus HCO 3 show a more complex pattern
(Figure 10c). For rivers with high HCO
3 concentrations,
the sample is above 1:1 line, which indicates that extra Ca2+
and/or Mg2+ can be attributed by sulfates. Most of these
rivers drains the source areas of the Xijiang, particularly the
Nanpanjiang and Beipanjiang drainage basins. For rivers
with median HCO
3 concentrations, the ratio approaches the
1:1 line, which indicates the carbonate dissolution. Meanwhile, for rivers with low HCO
3 concentrations, the ratio is
below the 1:1 line, which indicates that extra HCO
3 is
attributed by sodium and potassium aluminosilicates weathering. All samples of the Dongjiang and some of the Xijiang
and Beijiang draining silicate areas show such character2
istics. The plot of (Ca2+ + Mg2+) versus (HCO
3 + SO4 )
(Figure 10d) are close to the 1:1 line for samples with high
2
concentration of HCO
3 + SO4 , which indicates that the
water chemistry of these rivers are controlled mainly by
sulfates and carbonates. Samples with low concentrations of
2
HCO
3 + SO4 plot below the 1:1 line, indicating that extra
HCO3 is contributed by silicate weathering. Again, all
stations of the Dongjiang and some of the Xijiang and
Beijiang show such characteristics.
[22] More quantitative calculations on source of solutes
can be conducted using mass balance approach and generally there are two kinds of methods: direct/forward method
[Garrels and Mackenzie, 1967; Berner et al., 1983; Velbel,
1986; Meybeck, 1987; Amiotte-Suchet and Probst, 1993;
Benedetti et al., 2003; Qin et al., 2006] and indirect/inverse
method [Alle`gre and Lewin, 1989; Negrel et al., 1993;
Gaillardet et al., 1999; Roy et al., 1999]. In this study,
the forward method was employed to decipher the contributions of carbonate, silicate and evaporite weathering in
Table 5. Dilution Effects of Major Ions and Total Dissolved
Solids at Stations of Gaoyao, Shijiao, and Buluoa
Gaoyao
Shijiao
Boluo
Major ions
b
r
b
r
b
r
Ca2+
Mg2+
Na+ + K+
Cl
SO2
4
HCO
3
Total
Dissolved
Solids
0.072
0.147
0.028
0.060
0.134
0.063
0.062
0.000
0.000
0.590
0.158
0.000
0.000
0.000
0.099
0.165
0.056
0.099
0.138
0.092
0.092
0.000
0.000
0.393
0.073
0.006
0.000
0.000
0.327
0.229
0.069
0.057
0.127
0.223
0.198
0.000
0.000
0.010
0.122
0.018
0.000
0.000
a
10 of 17
Values in bold indicates significant at the level of 0.05.
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Figure 8. Long-term trends of major ions and TDS at the most downstream stations of Xijiang,
Dongjiang, and Beijiang: (a) Gaoyao, (b) Shijiao, and (c) Boluo (tau: the seasonal Kendall statistic; r: the
significance level; slope: the seasonal Kendal slope estimator, indicating the rate of change (mg/l/year)).
the Zhujiang waters. The forward method of mass balance is
a simple budget to allocate the dissolved constituents to the
corresponding source minerals by a series of steps [e.g.,
Garrels and Mackenzie, 1967; Meybeck, 1987]. The mass
balance equation for the element X in the dissolved load (in
molar concentration) can be written as
½Xriv ¼ ½Xcyc þ ½Xeva þ ½Xcar þ ½Xsil þ ½Xanth
Simplications can be further made for the different elements
as follows:
½Cl*riv ¼ ½Cleva
ð4Þ
ð2Þ
Where, riv = river; cyc = cyclic source; eva = evaporite
source; car = carbonate source; sil = silicate source; anth =
anthropogenic source.
[23] As discussed above, the atmosphere correction for
cyclic input was not carried out in this study because of its
minor influence in water chemistry in the Zhujiang waters.
The other simplification in this method has been made by
assuming there is little anthropogenic source in the Zhujiang
waters because of difficulty quantifying its influence. On
the basis of the above two assumptions, equation (2) can be
simplified as equation (3) as follows:
* ¼ ½X þ ½X þ ½X
½Xriv
eva
car
sil
ð3Þ
Figure 9. Plot of chloride concentration in the Zhujiang
waters against the distance from the sea. Solid circles
represent the Xijiang main channel stations, and open
circles represent the tributary stations.
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Figure 10. Plots of (a) (Na+ + K+) versus Cl, (b) (Ca2+ + Mg2+) versus HCO3, (c) (Ca2+ + Mg2+)
2+
+ Mg2+) versus (HCO3 + SO2
versus SO2
4 , and (d) (Ca
4 ).
½Na*riv ¼ ½Cleva þ ½Nasil
ð5Þ
* ¼ ½K ½Kriv
sil
ð6Þ
* ¼ ½SO ½SO4 riv
4 eva
ð7Þ
* ¼ ½SO þ ½Ca þ ½Ca
½Cariv
4 eva
car
sil
ð8Þ
* ¼ ½Mg þ ½Mg
½Mgriv
car
sil
ð9Þ
accompanying sulfide oxidation); (3) except evaporitederived fraction, sodium is from silicates (equation (5));
(4) all potassium comes from silicates (equation (6)); and
(5) to facilitate the calculation of equation (8) and (9), a Ca/
Na ratio of 0.4 and a Mg/Na ratio of 0.2 for silicate fraction
½HCO3 *riv ¼ ½HCO3 car þ ½HCO3 sil
¼ 2½Cacar þ2½Mgcar þ2½Casil þ2½Mgsil þ ½Nasil þ ½Ksil
ð10Þ
[24] The assumptions of simplification of equation (3)
include (1) all chloride comes from halite (equation (4)); (2)
all sulfate comes from gypsum (equation (7), which would
neglect the sulfate contribution from sulfide oxidation and
underestimate Na and Ca from carbonates and silicates
Figure 11. Fractions of the total dissolved load (in mass
units) from evaporite, carbonate, and silicate weathering
using forward mass balance calculation. Legends are same
as in Figure 5.
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Figure 12. Significant increasing trends of SO42 at station Qianjiang (number 9), Wuxuan (number
10), Dahuangjiangkou (number 11), Liuzhou (number 35), and Pingle (number 57) during the period of
1958 –1990. The long-term variations of pH and HCO3 at these stations are also shown.
are used in this study based on rivers draining purely silicate
terrains (such as stations 54, 64, 66, 67, 72, and 74). The
overall result shows that on average 68% (22 – 92%) of total
dissolved load comes from carbonate weathering, 22% (2 –
68%) from silicate weathering, and 10% (3 – 24%) from
evaporite weathering respectively (Figure 11). Silicate
weathering dominates the solute source in the Dongjiang
River stations, while carbonate weathering dominates most
of the Beijiang and Xijiang River stations, especailly along
the Xijiang main stem. The slightly higher contribution
from evaporite weathering calculated in this study compared
with the result of Gaillardet et al. [1999] (less than 5%) may
be due to not correcting for cyclic sources and not considering sulfide oxidation like mentioned above. Besides,
neglecting anthropogenic sources in the mass balance cal+
culations can be another factor, since Cl, SO2
4 and Na
are ions mostly affected by human activities [Berner and
Berner, 1987]. Some of the evidences of anthropogenic
influences in the Zhujiang will be discussed in the following
section.
6. Anthropogenic Influences
[25] Like the most rivers in the world, the water chemsitry
of the Zhujiang has also suffered from anthropogenic
influences in the drainage basin. The Zhujiang flows
through four provinces of South China, including the loci
of heavy industry (Guizhou and Guangxi provinces) and the
region experiencing the most rapid economic development,
(Guangdong Province). On the basis of long-term data
series, anthropogenic influences on water quality can be
detected from the natural fluctuations [Knutsson, 1994;
Chen et al., 2002, 2005]. By employing long-term trend
analysis, anthropogenic impacts on the water chemistry
were examined in the Zhujiang Basin.
[26] Significant increasing trends of SO2
4 concentration
have been detected at the upper main channel sections and
some principal tributaries of the Xijiang during the period
1958 – 1990. Figure 12 shows the increasing trends of
SO2
4 at station Qianjiang (number 9), Wuxuan (number 10),
Dahuangjiangkou (number 11), Liuzhou (number 35), and
Pingle (number 57). The rivers with significant increasing
trends drain source areas of the Xijiang where severe
acid deposition has been reported since the 1970s [Zhao
and Sun, 1986; Larssen et al., 1999]. These include the
Hongshuihe section (downstream of Nanpanjiang in Yunnan
and Beipanjiang in Guizhou), the Qianjiang section,
Xunjiang section, and the Liujiang and Guijiang tributaries
in Guangxi. Acid deposition is formed because of sulfur-rich
coal combustion, which contributed more than 3/4 of the
total energy production of China during recent years and
continues to be the major energy source for the near future
[Larssen et al., 1999]. However, unlike some noncarbonate
rivers in North America, Scandinavia, and Central Europe
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increasing chloride concentration in river waters [Berner
and Berner, 1996; Chen et al., 2005].
[28] Decreasing trends of some major ions and TDS
observed at station Boluo (Figure 8c), the most downstream
station of the Dongjiang, coincides with decreasing sediment load (Figure 13a). The double mass plot of cumulative
annual sediment load versus cumulative annual water
discharge can provide a means of distinguishing the effects
of human activities and climate change [Walling, 1995].
Figure 13b showed the double mass plot of cumulative
annual sediment load versus water discharge at station
Boluo of the Dongjiang, where two breaks around the year
1973 and 1990 can be observed, which might reflect
sediment trapping activities, such as reservoir construction,
water diversion and reforestation. Documentary sources
from PRWRC indicate that the Dongjiang is the most
regulated of the three rivers with large-scale multipurpose
water resource development since the late 1960s, such as
flood control, electricity generation, farm irrigation and
public water supply for the Pearl River Delta region. Three
large reservoirs were constructed in the 1960s and 1970s.
The total reservoir storage capacity in the Dongjiang subbasin is more than 80% of annual discharge at the most
downstream station Boluo (www.pearlwater.gov.cn)
(Table 6). In the Beijiang, one large reservoir was constructed
in 1999, and began to play its role in regulating flood and
irrigation. In the Xijiang, there are no major controlling
reservoirs in the main channel at present, but two large
structures are under design phase. Although the water
discharge of the Zhujiang has not been greatly impacted
by water regulation activities until recently, some dissolved
ions show decreasing trends related to reduced sediment
load by reforestation and reservoir construction. An intensification of the reforestation policy coupled with rapid
reservoir development in the Zhujiang Basin, will likely
cause more significant anthropogenic impacts on water
chemistry of the river waters in the future.
7. Fluxes From Land to Sea
Figure 13. (a) Long-term trend of annual sediment load at
station Boluo, (b) double mass plot of cumulative annual
sediment load versus cumulative annual water discharge at
station Boluo, and (c) long-term trend of annual TDS flux at
station Boluo.
[Hultman, 1989], no river acidification and significant
decreasing trend of HCO
3 are detected in rivers because
of the buffering effects of extensive spreads of carbonate
rocks in these regions (Figure 12).
[27] A significant increasing trend of Cl concentration
was detected at station Boluo, the most downstream station
of the Dongjiang, especially in the later 1990s (Figure 8c).
The possible sources of chloride can be attributed to
domestic and industrial wastewater discharge, chlorination
of public water supplies, and fertilizer application. Also,
return water from irrigation can play an important role in
[29] Gaoyao, Shijiao and Buluo, the most downstream
stations of Xijiang, Beijiang, and Dongjiang respectively,
were selected to calculate the fluxs of dissolved solids from
the Zhujiang to the South China Sea. The flux input from
smaller rivers draining the delta region was not included.
Table 6. Summary Information of Large and Medium Reservoirs
Constructed in the Zhujiang Basina
Large Reservoirb
Medium Reservoirc
Total
Storage
Storage
Storage
Capacity,
Capacity,
Capacity,
9 3
9 3
Water System Number 10 m Number 10 m Number 109m3
Xijiang
24
14.7
212
6
236
20.6
Beijiang
6
3.8
41
1.2
47
5
Dongjiang
4
17.2
35
0.8
39
18
the Pearl Delta
5
1.5
60
1.6
65
3.1
Total
39
37.2
348
9.6
387
46.7
a
From Pearl River Water Resources Committee (PRWRC) Web site http://
www.pearlwater.gov.cn/index.jsp).
b
Capacity of large reservoirs is over 108 m3.
c
Capacity of the medium reservoirs is from 107 million to 108 million m3.
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ZHANG ET AL.: WATER CHEMISTRY OF THE ZHUJIANG
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Table 7. Fluxes of Major Dissolved Ions of the Zhujiang and Other World Riversa
River
Zhujiang
(excluding the
Delta region)
Xijiang
Beijiang
Dongjiang
Xijiang
Changjiang
Huanghe
GangesBrahmaputra
Lena
Amazon
Orinoco
World Total
Area,
106 km2
Discharge,
109 m3/yr
Total
Dissolved
Solids
Ca2+
Mg2+
Na+
HCO
3
SO2
4
Cl
-
27.9
2.57
0.77
-
this study
this study
this study
this study
Degens et al. [1987]
Chen et al. [2002]
Chen et al. [2005]
Galy and
France-Lanord [1999]
Huh et al. [1998]
Stallard and
Edmond [1983]
Edmond et al. [1996]
Galy and France-Lanord [1999]
K+
b
SiO2
0.42
283.3
41.8
6.89
1.15
2.36
0.35
0.04
0.03
0.35
1.95
0.75
1.48
218.1
41.9
23.3
222
899
32.9
1071
35.2
5.3
1.3
42.1
153.9
13.1
129.5
5.80
0.96
0.13
27.0
1.2
18.5
0.99
0.11
0.04
5.7
0.7
4.5
1.90b
0.27b
0.19b
4.5b
1.8b
4.2
2.3
23.7
3.50
0.71
101.7
5.5
72.3
2.05
0.38
0.14
10.7
2.5
12.7
0.65
0.08
0.04
3.8
1.5
2.1
10.1
12.9
2.44
4.69
532
6930
50.6
324.6
7.2
38.0
1.7
7.4
3.3
10.8
0.3
6.3
25.8
151.8
4.8
14.9
4.5
7.7
2.9
87.8
1.00
1100
37400
51.3
3843.0
5.9
500.0
1.3
126.0
2.3
195.0
0.8
48.0
21.5
1946.0
4.6
202.0
1.3
217.0
13.5
609
Source
a
Units are 106 tonnes/yr.
Sum of Na+ and K+.
b
The annual fluxes of major elements and total dissolved
solids at each station are calculated by the product of annual
water discharge and the mean concentrations of major
elements. The total fluxes transported by the Zhujiang is
calculated by summing the multiyear averaged fluxes from
the above three rivers (Table 7).
[30] During the period of 1958 – 2002, the Zhujiang transports about 41.8 106 tonnes/year of TDS into SCS on
2+
are the dominant dissolved
average. HCO
3 and Ca
components, which account for 83.3% of the total dissolved
solids of the Zhujiang river waters. The total fluxes of total
dissolved solids transported from the Zhujiang is 27.2% of
that transported by the Changjiang, 3.2 times of that by the
Huanghe, and accounts for about 1.1% of total dissolved
fluxes transported by rivers all over the world.
[31] Figure 8 shows that TDS concentrations at the three
downstream stations of the Xijiang, Beijiang and Dongjiang
have significant decreasing trends. However, the significant
decreasing trend of TDS flux was detected only at station
Boluo of the Dongjiang (Figure 13c). The flux of the
Xijiang calculated in this study is much smaller compared
with the flux of the Xijiang compiled by Degens et al.
[1987], which implies the decreasing TDS flux transported
by the Xijiang since the 1980s.
8. Conclusions
[32] The Zhujiang is the largest river system in South
China playing an important role for economic development
of upstream regions of southwest China and the downstream
delta region. With carbonates widely distributed in the
Zhujiang Basin, the water chemistry is dominated by
2+
are the dominant
carbonate weathering. HCO
3 and Ca
dissolved components, accounting for 83.3% of the total
dissolved solids of the Zhujiang waters. Flux calculations
for total dissolved solids for the Zhujiang are 41.8 106 tonnes/year. The Zhujiang flux is much smaller than
the larger Changjiang basin but considerably larger than the
Huanghe basin. The flux also exceeds 1% of the estimated
global dissolved load flux [Galy and France-Lanord, 1999]
underlining the significance of the river basin for nutrient
supply to the South China Sea.
[33] The impacts of anthropogenic activities on the
water chemistry have been detected in the Zhujiang
concentration has been increasing in the
Basin. SO2
4
upper Xijiang region due to acid deposition. Cl concentration has been increasing in the Dongjiang Basin probably due to domestic and industrial wastewater discharge,
chlorination of public water supplies, and enriched irrigation return water. Some major ions and TDS have
decreased at the most downstream station of the Dongjiang in association with decreasing sediment load. It is
postulated that land use change in the Zhujiang Basin,
most notably through a vigorous reforestation policy and
by rapid reservoir development, will lead to more significant anthropogenic impacts on water chemistry in the
future.
[34] Acknowledgments. This research was funded by SARCS (project 92/01/Carbon) and the National Uinversity of Singapore (grant R-109000-054-112). The paper benefited from constructive comments by two
anonymous reviewers and Suzanne Anderson.
References
Alle`gre, C. J., and E. Lewin (1989), Chemical structure and history of the
Earth: Evidence from global non-linear inversion of isotopic data in a
three-box model, Earth Planet. Sci. Lett., 96, 61 – 88.
Amiotte-Suchet, P., and J. L. Probst (1993), Modelling of atmospheric CO2
consumption by chemical weathering of rocks: Application to the Garonne, Congo and Amazon basins, Chem. Geol., 107, 205 – 210.
Benedetti, M. F., et al. (2003), Chemical weathering of basaltic lava flows
undergoing extreme climatic conditions: the water geochemistry record,
Chem. Geol., 201, 1 – 17.
Berner, K. E., and R. A. Berner (1987), The Global Water Cycle: Geochemistry and Environment, Prentice-Hall, Upper Saddle River, N. J.
Berner, K. E., and R. A. Berner (1996), Global Environment: Water, Air,
and Geochemical cycles, Prentice Hall, Upper Saddle River, N. J.
Berner, R. A., A. C. Lassaga, and R. M. Garrels (1983), The carbonatesilicate geochemical cycle and its effect on atmospheric carbon dioxide
over the past 100 million years, Am. J. Sci., 284, 1183 – 1192.
Chen, J., and D. He (1999), Chemical characteristics and genesis of major
ions in the Pearl River Basin, Acta Sci. Nat. Univ. Pekinensi, 35, 786 –
793, (in Chinese).
Chen, J., F. Wang, X. Xia, and L. Zhang (2002), Major element chemistry
of the Changjiang (Yangtze River), Chem. Geol., 187, 231 – 255.
15 of 17
F01011
ZHANG ET AL.: WATER CHEMISTRY OF THE ZHUJIANG
Chen, J., F. Wang, M. Meybeck, D. He, X. Xia, and L. Zhang (2005),
Spatial and temporal analysis of water chemistry records (1958 – 2000)
in the Huanghe (Yellow River) basin, Global Biogeochem. Cycles, 19,
GB3016, doi:10.1029/2004GB002325.
Chen, X., Y. Zong, E. Zhang, J. Xu, and S. Li (2001), Human impacts on
the Changjiang (Yangtze) River basin, China, with special reference to
the impacts on the dry season water discharge into the sea, Geomorphology, 41, 111 – 123.
Clarke, R. W. (1916), The Data of Geochemistry, U.S. Geol. Surv. Bull.
616, 3rd ed., 821 pp., U.S. Gov. Print. Off., Washington, D. C.
Degens, E. T., (Ed.) (1989), Perspectives on Biogeochemistry, 423 pp.,
Springer, New York.
Degens, E. T., S. Kempe, and W. Gan, (Eds.) (1987), Transport of Carbon
and Minerals in Major World Rivers, part 4, SCOPE/UNEP, 64, 512 pp.,
Mitt. Geol.-Pala¨ont. Inst. Univ. Hamburg, Hamburg.
Edmond, J. M., M. R. Palmer, C. I. Measures, E. T. Brown, and Y. Huh
(1996), Fluvial geochemistry of the eastern slope of the northeastern
Andes and its foredeep in the drainage of the Orinoco in Colombia and
Venezuela, Geochim. Cosmochim. Acta, 60, 2949 – 2976.
Gaillardet, J., B. Dupre, P. Louvat, and C. J. Alle`gre (1999), Global silicate
weathering and CO2 consumption rates deduced from the chemistry of
large rivers, Chem. Geol., 159, 3 – 30.
Galy, A., and C. France-Lanord (1999), Weathering processes in the
Ganges-Brahmaputra basin and the riverine alkalinity budget, Chem.
Geol., 159, 31 – 60.
Gan, W. B. (1985), Hydrochemistry of the Yangtze River Basin, in Transport of Carbon and Minerals in Major World Rivers, part 3, SCOPE/
UNEP, 58, edited by E. T. Degens, S. Kempe, and R. Herrera, 645 pp.,
Mitt. Geol.-Pala¨ont. Inst. Univ. Hamburg, Hamburg.
Garrels, R. M., and F. T. Mackenzie (1967), Origin of the chemical compositions of some springs and lakes: Equilibrium concepts in natural
water systems, Am. Chem. Soc. Adv. Chem. Ser., 67, 222 – 242.
Gibbs, R. J. (1970), Mechanisms controlling world water chemistry,
Science, 170, 1088 – 1090.
Gibbs, R. J. (1972), Water chemistry of the Amazon River, Geochim.
Cosmochim. Acta, 36, 1061 – 1066.
Gordeev, V. V., and L. S. Sidorov (1993), Concentrations of major elements
and their outflow into the Laptev Sea by the Lena River, Mar. Chem., 43,
33 – 45.
Hirsch, R. M., and J. R. Slack (1984), A nonparametric trend test for
seasonal data with serial dependence, Water Resour. Res., 20, 727 – 732.
Hirsch, R. M., J. R. Slack, and R. A. Smith (1982), Techniques of trend
analysis for monthly water quality data, Water Resour. Res., 18, 107 –
121.
Hu, M. H., R. F. Stallard, and J. M. Edmond (1982), Major ion chemistry of
some large Chinese rivers, Nature, 298, 550 – 553.
Huh, Y., G. Panteleyev, D. Babich, A. Zaitsev, and J. M. Edmond (1998),
The fluvial geochemistry of the rivers of Eastern Siberia: II. Tributaries of
the Lena, Omoloy, Yana, Indigirka/Kolyma, and Anadyr draining the
collisional/accretionary zone of the Verkhoyansk and Cherskiy ranges,
Geochim. Cosmochim. Acta, 62, 2053 – 2075.
Hultman, B. (1989), Acidification, in Global Freshwater Quality, A First
Assessment, edited by M. Meybeck, D. Chapman and R. Helmer,
pp.195 – 217, Blackwell, Malden, Mass.
Jarvie, H. P., C. Neal, D. V. Leach, G. P. Ryland, W. A. House, and
A. J. Robson (1997), Major ion concentrations and the inorganic
carbon chemistry of the Humber rivers, Sci. Total Environ., 194/195,
285 – 302.
Kennedy, Y. C., and R. L. Malcolm (1977), Geochemistry of the Mattole
River of Northern California, USGS Open-File Rep. 78-205, 324 pp.
Knutsson, G. (1994), Trends in the acidification of groundwater quality
management, in Groundwater Quality Management, edited by K. Kovar
and J. Soveri, IAHS Publ., 220, 107 – 118.
Larssen, T., H. M. Seip, A. Semb, J. Mulder, I. P. Muniz, R. D. Vogt,
E. Lydersen, V. Angell, D. Tang, and O. Eilertsen (1999), Acid deposition and its effects in China: An overview, Environ. Sci. Policy, 2,
9 – 24.
Livingstone, D. A. (1963), Chemical Composition of Rivers and Lakes,
U.S. Geol. Surv. Prof. Pap., 440-G, 64 pp., U.S. Gov. Print. Off., Washington, D. C.
Lu, X. X. (2004), Vulnerability of water discharge of large Chinese rivers to
environmental changes: An overview, Reg. Environ. Change, 4, 182 –
191.
Lu, X. X., and D. L. Higgitt (1998), Recent changes of sediment yield in the
upper Yangtze, China, Environ. Manage., 22, 697 – 709.
Lu, X. X., and R. Y. Siew (2006), Water discharge and sediment flux
changes in the Lower Mekong River: Potential impact of Chinese dams,
Hydrol. Earth System Sci., 10, 181 – 195.
Meybeck, M. (1987), Global chemical weathering of surficial rocks estimated from river dissolved loads, Am. J. Sci., 287, 401 – 428.
F01011
Meybeck, M. (1998), Man and river interface: Multiple impacts on water
and particulates chemistry illustrated in the Seine River basin, Hydrobiologia, 373, 1 – 20.
Meybeck, M. (2003), Global analysis of river systems: From Earth system
controls to Anthropocene syndromes, Philos. Trans. R. Soc. London Ser.
B, 358, 1935 – 1955.
Meybeck, M., and R. Helmer (1989), The quality of rivers: From pristine
stage to global pollution, Palaeogeogr. Palaeoclimatol. Palaeoecol., 75,
283 – 309.
Negrel, P., C. J. Alle`gre, B. Dupre, and E. Lewin (1993), Erosion sources
determined by inversion of major and trace element ratios in river water:
The Congo Basin case, Earth Planet. Sci. Lett., 120, 59 – 76.
Nkounkou, R. R., and J. L. Probst (1987), Hydrology and geochemistry of
the Congo River system, in Transport of Carbon and Minerals in Major
World Rivers, part 4, SCOPE/UNEP, 64, edited by E. T. Degens,
S. Kempe and W. Gan, pp. 483 – 508, Mitt. Geol.-Pala¨ont. Inst. Univ.
Hamburg, Hamburg.
Pearl River Water Resources Committee (PRWRC) (1991), The Zhujiang
Archive (in Chinese), vol. 1, Guangdong Sci. and Technol. Press,
Guangzhou, China.
Piper, A. M. (1944), A graphic procedure in the geochemical interpretation
of water analysis, Eos Trans. AGU, 25, 914 – 923.
Probst, J. L., R. R. Nkounkou, G. Krempp, J. P. Bricquet, J. P. Thie´baux,
and J. C. Olivry (1992), Dissolved major elements exported by the Congo
and the Ubangi rivers during the period 1987 – 1989, J. Hydrol., 135,
237 – 257.
Qin, J., Y. Huh, J. M. Edmond, G. Du, and J. Ran (2006), Chemical and
physical weathering in the Min Jiang, a headwater tributary of the
Yangtze River, Chem. Geol., 227, 53 – 69.
Richey, J. E., E. Victoria, R. L. Salati and B. R. Forsberg (1991), The
biogeochemistry of a major river system: The Amazon case study, in
Biogeochemistry of Major World Rivers, SCOPE, vol. 42, edited by
E. T. Degens, S. Kempe and J. Richey, pp. 57 – 74, John-Wiley, Hoboken,
N. J.
Roy, S., J. Gaillardet, and C. J. Alle`gre (1999), Geochemistry of dissolved
and suspended loads of the Seine River, France: Anthropic impact, carbonate and silicate weathering, Geochim. Cosmochim. Acta., 63(9),
1277 – 1292.
Sarin, M. M., and S. Krishnaswami (1984), Major ion chemistry of the
Ganga-Brahmaputra river systems, India, Nature, 312, 538 – 541.
Sarin, M. M., S. Krishnaswami, K. Dilli, B. L. K. Somayajulu, and W. S.
Moore (1989), Major ion chemistry of the Ganga-Brahmaputra river
system: Weathering processes and fluxes to the Bay of Bengal, Geochim.
Cosmochim. Acta., 53, 997 – 1009.
Schwartz, H. E., J. Emel, W. J. Dickens, P. Rogers, and J. Thompson
(1990), Water quality and flows, in The Earth as Transformed by Human
Action, edited by B. L. Turner, W. C. Clark, R. W. Kates, J. F. Richards,
J. T. Matthews and W. B. Meyer, pp. 253 – 270, Cambridge Univ. Press,
New York.
Stallard, R. F., and J. M. Edmond (1981), Geochemistry of the Amazon:
1. Precipitation chemistry and the marine contribution to the dissolved
load at the time of peak discharge, J. Geophys. Res., 86, 9844 – 9858.
Stallard, R. F., and J. M. Edmond (1983), Geochemistry of the Amazon:
2. The influence of geology and weathering environment on the dissolved
load, J. Geophys. Res., 88, 9671 – 9688.
Stallard, R. F., and J. M. Edmond (1987), Geochemistry of the Amazon:
3. Weathering chemistry and limits to dissolved inputs, J. Geophys. Res.,
92, 8293 – 8302.
Turner, B. L., W. C. Clark, R. W. Kates, J. F. Richards, J. T. Matthews, and
W. B. Meyer (1990), The Earth as Transformed by Human Action, Cambridge Univ. Press, New York.
Vegas-Vilarrubia, T., and J. Paolini (1985), Some physical and chemical characteristics of black water rivers in Venezuela, a preliminary
report, in Transport of Carbon and Minerals in Major World Rivers,
part 3, SCOPE/UNEP, 58, edited by E. T. Degens, S. Kempe and
R. Herrera, pp.191 – 196, Mitt. Geol.-Pala¨ont. Inst. Univ. Hamburg,
Hamburg.
Velbel, M. A. (1986), The mathematical basis for determining rates of
geochemical and geomorphic processes in small forested watersheds by
mass balance: Examples and implications, in Rates of Chemical Weathering of Rocks and Minerals, edited by S. M. Coleman and D. P. Delthier,
pp. 439 – 451, Elsevier, New York.
Walling, D. E. (1995), Suspended sediment yields in a changing environment, in Changing River Channels, edited by A. Gurnell and G. Petts,
pp. 149 – 176, John Wiley, Hoboken, N. J.
Walling, D. E., and B. W. Webb (1986), Solutes in river systems, in Solute
Processes, edited by S. T. Trudgill, pp. 251 – 327, John Wiley, Hoboken,
N. J.
Xu, J. X. (2004), A study of anthropogenic seasonal rivers in China,
Catena, 55, 17 – 32.
16 of 17
F01011
ZHANG ET AL.: WATER CHEMISTRY OF THE ZHUJIANG
Yuretich, R. F., D. A. Crerar, D. J. J. Kinsman, J. L. Means, and M. P.
Borcsik (1981), Hydrogeochemistry of the New Jersey Coastal Plain:
1. Major element cycles in precipitation and river water, Chem. Geol.,
33, 1 – 21.
Zhang, J., W. W. Huang, M. G. Liu, and Q. Zhou (1990), Drainage
basin weathering and major element transport of two large Chinese
rivers (Huanghe and Changjiang), J. Geophys. Res., 95, 13,277 –
13,288.
Zhang, J., W. W. Huang, R. Letolle, and C. Jusserand (1995a), Major
element chemistry of the Huanghe (Yellow River), China: Weathering
processes and chemical fluxes, J. Hydrol., 168, 173 – 203.
Zhang, J., K. Takahashi, H. Wushiki, S. Yabuki, J.-M. Xiong, and
A. Masuda (1995b), Water geochemistry of the rivers around the
F01011
Taklimakan Desert (NW China): Crustal weathering and evaporation
processes in arid land, Chem. Geol., 119, 225 – 237.
Zhao, D., and B. Sun (1986), Air pollution and acid rain in China, Ambio,
15, 2 – 5.
C.-T. A. Chen, Institute of Marine Geology and Chemistry, National Sun
Yat-Sen University, P.O. Box 59 – 60, Kaohsiung, 80424 Taiwan.
J.-T. Han and H.-G. Sun, Institute of Geology and Geophysics, Chinese
Academy of Sciences, Beijing 100029, China.
D. L. Higgitt, X. X. Lu, and S.-R. Zhang, Department of Geography,
National University of Singapore, Arts Link 1, Singapore 117570.
([email protected])
17 of 17