Chemical Geology 214 (2005) 223 – 248
www.elsevier.com/locate/chemgeo
Chemical weathering of silicate rocks in Aldan Shield and
Baikal Uplift: insights from long-term seasonal
measurements of solute fluxes in rivers
E.A. Zakharovaa,b, O.S. Pokrovskya,*, B. Dupréa, M.B. Zaslavskayab
b
a
Laboratoire de Mécanismes et Transfert en Géologie, CNRS, 14, Avenue Edouard Belin, 31400 Toulouse, France
Department of Hydrology, Faculty of Geography, Moscow State University, Vorobievy Gory 1, 119899 Moscow, Russia
Received 19 June 2003; accepted 10 October 2004
Abstract
A reassessment of available information from the Russian Hydrological Survey on long-term seasonal measurements of
water, suspended matter and dissolved major element discharges in ~30 small and large watersheds draining acid silicate rocks
(granites, gneisses, quartzites, shales) of the Aldan Shield and Baikal Uplift was combined with new data on river water
chemistry for three granitic watersheds in order to calculate the fluxes of elements due to chemical weathering. In accord with
data on world rivers, a positive correlation between chemical erosion rate and runoff is observed. The majority of cations are
removed during summer monsoon. The spring flood yields 10–20% of the annual flux and the winter season accounts for only
5–15%. The mean multi-annual flux of total dissolved solid which is largely dominated by Ca (60–80%) on the Siberian Craton
is comparable with that of temperate zones but higher than that of the Canadian Shield for similar runoff values, rock
composition and annual temperatures. Important element recycling due to litter degradation and weathering acceleration via
organic ligands produced by abundant vegetation over permafrost soils is invoked to explain these results.
D 2004 Published by Elsevier B.V.
Keywords: Aldan; Baikal; Granites; Weathering; Chemical composition; River water
1. Introduction
Over the last 30 years, a vast amount of information
has been collected on the chemical erosion of rocks at
the Earth’s surface. Weathering of silicate rocks, which
is largely responsible for CO2 consumption from the
* Corresponding author. Fax: +33 5 61 33 25 60.
E-mail address: [email protected] (O.S. Pokrovsky).
0009-2541/$ - see front matter D 2004 Published by Elsevier B.V.
doi:10.1016/j.chemgeo.2004.10.003
atmosphere on the continents, has been extensively
studied in both tropical and temperate environments
(Dunne, 1978; Stallard and Edmond, 1983; Yuretich et
al., 1993; Edmond et al., 1995; Gaillardet et al., 1995,
1997, 1999a,b; Dupré et al., 1996; Blum et al., 1998;
Viers et al., 1997, 2000; Oliva et al., 1999; Dessert et
al., 2001). At the same time, boreal, glacial and cold
continental regions have received less attention (Reynolds and Johnson, 1972; Ugolini, 1986; Drever and
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E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
Zobrist, 1992; Gislason et al., 1996; Clow and Drever,
1996; Anderson et al., 1997, 2000, 2003; Hodson et al.,
2000; Millot et al., 2002, 2003; Gaillardet et al., 2003;
Oliva et al., 2003). Boreal regions such as southern
Siberia are likely to play a crucial role in regulating of
CO2 in the atmosphere because they serve as an
important site for carbon storage reservoirs in organicrich permafrost soils as well as in the vegetation pool.
Because the runoff and temperature exert the major
control on chemical weathering intensity of silicate
rocks in surficial aquatic environments (Bluth and
Kump, 1994; White and Blum, 1995; White et al.,
1999a; Dessert et al., 2003; Oliva et al., 2003), one
can suggest that the chemical weathering rates in cold
regions with continental climate are quite low.
However, in a series of pioneering papers of Huh
and co-workers devoted to fluvial geochemistry of
Siberian Craton rivers (Huh et al., 1998; Huh and
Edmond, 1999), it has been argued that the weathering intensity in these regions is comparable with that
of temperate zones even though the average temperature in Siberia is 10–20 8C lower. These authors
considered only short-time sampling series during the
summer period, mostly for large basins draining the
rocks of mixed lithology. Long-term systematic
observations of rivers from mainly granitic terrains
under glaciated or permafrost environments are still
lacking. This study bridges this gap by assessing a
large amount of data obtained from the Russian
Hydrological Survey on discharge and chemical
composition of rivers in southeast Siberia, mostly on
the Aldan Shield corresponding to long-term seasonal
observations. Our primary goal was to rigorously
estimate the chemical elements and suspended matter
fluxes for various size watersheds draining granitic
terrain and to compare them for other regions of the
world. Our secondary goal was to test the role of
various factors such as temperature, runoff, rock
composition and vegetation on overall erosion intensity in this permafrost dominated region.
2. Materials and methods
2.1. Lithology and permafrost
The studied area (650,000 km2 from 1048W,
508N and 1358W, 598N, Fig. 1) is situated within
two vast orographic structures of the Siberian
Craton: the Aldan–Stanovoy Shield and the Baikal
Uplift. It includes three drainage basins: the Lena
River, the Amur River and Lake Baikal. The
elevation varies from 400 to 3000 m with mountain
ranges being orientated from southwest to northeast.
Geologically, the platform consists of felsic Precambrian igneous and metamorphic acid rocks
(granites, gneisses, granodiorites) with some amount
of basalt, carbonate sedimentary rocks and alkaline
rocks, especially in Chara region (Salop, 1964,
1967). For Aldan Shield, the postmagmatic hydrothermal vein carbonate mineralization is not
reported. The Archaen carbonates are present only
in Federovskaya formation of Iengrskaya series and
in Jeltulinskaya series, where their proportion is
below 8%. As these strata account for less than
30% of total volume of the shield, the overall
proportion of carbonate rocks in Siberian granites is
less than 3% (Kulish, 1983; Yanshin, 1989).
According to Yanshin (1989), on the territory of
granulites of Aldan complex (~200,000 km2), the
proterozoic granitoids and gypersten–plagiocalse
gneisses of enderbite–charnokite series account for
~52%, ultramafic rocks constitute ~6%, and the rest
(~42%) is represented by terrigenic highly aluminous shales (~24%), quartzites (~9%), primary
carbonato-terrigenic rocks (skapolite, andradite,
diopside-flogopite and pyroxenic metamorphic
rocks, ~6%), and marbles and calcifires (~3%).
Further geological and tectonic descriptions can be
found elsewhere (Korzhinsky, 1939; Puchtel et al.,
1993; Frost et al., 1998; Huh and Edmond, 1999).
Permafrost occurs throughout the studied area
(Shpolyanskaya, 1967). In the southeastern part, the
permafrost has a sporadic distribution. Its thickness
varies from 2–25 m in river valley bottoms to 25–50
m on the slopes. The temperature of permanently
frozen rocks at the depth of zero annual amplitude
ranges from 0.1 to 1 8C. In the northeast part and
in the Vitim basin, the permafrost thickness exceeds
200 m and mean rock temperature decreases to 4 8C.
In the most northern part, the permafrost thickness
reaches 500 m. Throughout the territory, the active
layer of permafrost thaws for a period of 2–3 months
during the summer. The thickness of active layer
ranges from 0.5 m on the slopes to 4 m on the valley
bottoms.
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
Fig. 1. Map of the area showing the rivers, hydrological station locations and orographic features. I: Mountain ridges and absolute elevations; II: glacier on the Kodar ridge. Rocks:
1=Precambrian granites, gneisses, granodiorites, 2=silicate terrigenic rocks (Jurassic shales, sandstones, argillites and quartzites), 3=carbonates (Cambrian limestones), and 4=igneous
basic rocks. Stations: A (crosses)=meteorological stations (Table 1), B (filled circles)=gauging stations of the Hydrological Survey (Tables 2 and 3), C (filled triangles)=gauging
stations on Chitinka and Ingoda rivers sampled in this study, and D (filled squares)=sampling points of Huh and Edmond (1999).
225
226
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
2.2. Vegetation and soils
The soils and vegetation of the region vary
significantly with altitude. The soils are mainly
cryobrown and cryopodzolic. Their main features
are relatively short profiles (0.3–0.5 m) and thick
humus horizon with a high amount of acidic, nonsaturated organic matter of fulvic nature. The soils
are enriched in Ca and Mg in comparison with
parental rocks (Nogina, 1964; Targulian, 1971). The
vegetation is represented by boreal forest which
covers three zones. At low elevation, the south taiga
zone is represented by larch and pine trees with
scattered birch and occupies areas southward of
528N and elevations to 900–1000 m. The middle
taiga zone at 900 to 1100–1200 m elevations is
represented by larch trees on mountain cryopodzol
and taiga peat-cryogenic soils (Histosols and various
Gleysols in the valleys and Lithosol Gelic Gleysols
and Gelic Regosols at 1100–1200 m). The high
elevation northern taiga zone (1200–1600 m) is
covered by sparse larch and cedar vegetation
developed on mountain cryogenic soils (Lithosols
associated with Dystric Podzoluvisols, Dystric
Cambisols and Gelic Cambisols). Tundra landscapes
with Gelic Gleysols and Regosols replace the taiga
zone at elevations above 1400–1900 m. In mountain
depressions southward from 528N, steppe and
forest–steppe vegetation is abundant. This part of
the region is characterized by the association of
Lithosols with Dystric Regosols and Dystric Podzoluvisols, and phreatic Chernozems predominate in
the inter-mountain depressions. These Chernozems
contain up to 6% of humus and the thickness of the
humus horizon is about 30–50 cm (FAO/UNESCO,
1978).
2.3. Climate and hydrology
The climate of the territory is semi-arid and
strongly continental with an extremely high annual
variability (Fig. 2A). Mean annual air temperature
varies from 0.5 8C in the south near Lake Baikal
to 8.5 8C in the northeast. The seasonal magnitude may exceed 1008C changing from +38 8C in
July to 65 8C in January. Atmospheric circulation
is stable during the winter and determined by
anticyclones. As a result, the precipitation is low.
In spring, which begins at the end of April,
cyclonic circulation brings dry cold air from the
west and northwest accompanied by strong winds.
Under these conditions, the snow often sublimates
before the melting. From the second part of June,
East Pacific cyclones penetrate as far as Lake
Baikal and bring abundant precipitation. This period
lasts for 2–2.5 months and is accompanied by the
highest air temperatures. The autumn is short, cold
and dry (Table 1).
The seasonal variation of precipitation (Fig. 2B)
is determined by atmospheric circulation while its
spatial distribution is controlled by orography. The
highest annual precipitation values were noted on
the northwest ridges, where it reaches 1200 mm at
the altitude of 1400 m (Station Khamar-Daban, Fig.
1). The lowest values (250–300 mm) were found in
the southern valleys close to Lake Baikal. Important
features of the region are strong storm events
occurring during the summer monsoon, providing
up to 200 mm precipitation per day.
The annual pattern of rivers discharge exhibits
very strong dependence on season and rain events
(Fig. 2B). During the five winter months, the rivers
carry only 5% of the annual discharge. Small rivers
may be completely frozen during 100–120 days
from December to March. The influence of groundwater input is less than 10% reaching 25–35% for
the large rivers. The proportion of spring flood flow
decreases from north to southwest and increases
with basin size. For the whole region, it does not
exceed 60% of annual flow. Annual river runoff
values vary from 30 to 900 mm and decrease from
north to south. They increase with elevation by
about 30–40 mm per 100 m altitude (Resources of
Surface Waters of the USSR, 1973a,b,c).
In the Baikal Uplift, lakes cover less than 1.2%
of the area. However, on the Aldan shield, from
10% to 20% of the high flat surfaces is occupied by
lakes. In the northern and eastern parts of the
territory, bogs and lakes occupy 10–30% of total
river watershed area.
2.4. Sampling and analysis
Water sampling and analysis methods applied at
the field works are similar to those of the Hydrological Survey (Semenov, 1977). Water was filtered
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
227
Fig. 2. Annual variations of precipitation (bars) and temperature (lines) regime at two meteorological stations (A), and water discharges for two
typical rivers of the region (B). The data are from Resources (1973).
through 0.5-Am ash-free paper filter and stored in
acid-cleaned 500-mL plastic or glass bottles. Temperature (F0.5 8C) and pH (F0.05 units) were measured
during sampling and alkalinity (F5%, detection limit
of 50 AM) was titrated on site within 1 day of
collection. All other components were analyzed in
laboratory within 2–3 days after sampling. Calcium
and magnesium were measured by volumetric titration
with EDTA (F2%, detection limit of 25 AM); sodium
and potassium were analyzed using flame atomic
absorption (F10%, detection limit of 0.05 mg/L), and
Si, Fe and SO4 were determined by spectrophotometry with molybdenum bleu, oxiquinoline and BaCl2,
respectively (uncertainty of F5% for all three
components, detection limits are 0.1 AM for Si and
Fe and 1 AM for SO4). Dissolved organic matter
concentration was approximated via permanganate
oxidation (PO) in an acidic medium (Semenov, 1977)
and expressed as gram of oxygen per liter.
For rivers of State Hydrological Survey, the total
suspended matter was determined by filtering water
through paper filters with a pore size of 0.8 Am to
collect a minimum weight sample of 0.1 g. The
grain size distribution was measured using standard
gravity granulometer by sedimentation in water
column.
228
Station on the map
Khuzhir
Barguzin reservoir
Nerchinsk
Chita
Mogocha
Khamar-Daban
Dal’durga
Aksha
Romanovka
Years
1990
1990
1990
1990
1990
1962–1985,
1990
1962–1965,
1990
1981–1985
1962–1990
Precipitation,
mm
pH
Ca
Mg
Na
K
HCO3
SO4
Cl
N-NO3
N-NH4
Concentration, mg/L
449
379
479
436
379
1417
5.8
6.6
6.5
6.2
6.1
1.0
1.8
4.7
4
2.9
0.49F0.1
0.2
0.3
0.5
0.4
0.5
0.34F0.1
0.9
0.8
4.7
1.1
1.6
0.36F0.12
0.6
0.7
1
0.8
0.9
0.19F0.08
1.8
4.3
8.2
8
3.2
2.40F0.8
1.3
3.2
5
5.8
4.6
1.36F0.4
0.9
1.5
2
1.6
1.9
0.98F0.4
16
0.32
0.49
0.25
0.32
0.08F0.04
0.23
0.54
0.39
0.08
0.39
0.32F0.2
453
6.4
1.42
0.55
0.50
0.4
4.71
2.97
1.14
0.38
0.62
383
361
6.5
6
1.07F0.5
0.46F0.1
0.97F0.4
0.45F0.3
0.40F0.21
0.53F0.1
6.29F1.2
3.28F1.0
2.12F0.5
1.32F0.7
0.95F0.3
1.25F0.4
0.18F0.1
0.07F0.02
0.33F0.18
0.14F0.06
0.53F0.2
0.69F0.3
The data comprises between 10 and 50 samplings per year for each station; the standard deviation is ~30% unless indicated.
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
Table 1
Mean annual precipitation and its average chemical composition measured on the stations of the Meteorological Network of the USSR and situated in the vicinity of the studied area
(Savenko et al., in preparation)
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
2.5. Sources of information and estimation methods
Our study is based on data obtained from
systematic surveys by the Hydrometeorological State
Committee of the former USSR Goskomgidromet
and later Roskomgidromet. These data are published
in the annual issues of the State Water Cadastre of
three studied regions: Baikal, Lena and Amur Basins
(Hydrological Yearbooks and State Gidromet, 1954–
1975a,b) and further generalized in Resources of
Surface Waters of the USSR, 1973a,b,c. Twenty-two
rivers draining Precambrian granitoid terrain were
retained for further discussion (Fig. 1). For comparison, a river draining essentially basic rocks (Amalat,
No. 27) was also included. The river watersheds size
varies from 200 to 186,000 km2. The data from the
Hydrological Survey include for each 24 hydrological stations the water daily discharge and from 4
to 11 measurements per year of major cations,
anions, silica and iron concentrations and 15–30
measurements per year of total suspended matter
(SM). Daily discharge values for all studied rivers
were obtained from the stage–discharge rating curve
established by the Hydrological Survey for each
gauging station according to International Standards
(ISO, 1983). Chemical analyses are described in
Section 2.4.
For two rivers of Amur basin we used the
original data obtained during field studies in 1983–
1986 at two stations on the Ingoda river (Nos. 12
and 13) and one station on the Chitinka river (No.
8). Our data on rivers Chitinka and Ingoda comprise
results of monitoring during the ice-free periods in
1984, 1985 and 1986 and includes about 30–40
samplings per year.
Concentrations of calcium, magnesium, and sum of
cations for most rivers demonstrate a strong exponential dependence on water discharge. Because this
dependence is valid over the full period of observations (1954–1975), it was used for estimation of mean
annual concentrations. For this, full set of data from
1954 to 1975 were used to generate the coefficients k
and n in the Eq. (1)
Ci ¼ k Qin
ð1Þ
where C i is measured element concentration for a
given day of the year, Q i is water discharge for this
229
day, k and n are the empirical constants for each
river. Examples of C vs. Q dependence for some
rivers and the range of k and n parameters are
given in the appendix (Fig. A1 and Table A1,
respectively). Afterwards, the mean annual water
discharge value available for the period of observations (Resources of Surface waters, 1954–1975) was
used to calculate the mean multi-year concentration
of each element (Table 2) using Eq. (1). Similar
method was used by Gordeev and Sidorov (1993) for
estimation of mean monthly and annual element
concentrations in rivers of Lena Basin.
For several watersheds, this technique was
compared with more accurate combined method of
chemical flux calculation. In this method, we used
exponential relation between C and Q (Eq. (1)) for
calculating daily concentration from the daily discharge exclusively for the high water periods (spring
melt and summer monsoons, Fig. 3). For the low
water level period, when both the discharge and
element concentration are quasi-constant, the daily
concentrations were calculated by time linear interpolation (Zaslavskaya and Tikhotskaya, 1978). This
allowed to calculate the mean annual dischargeweighted concentration for each element. Because
the water flow during the low water period on studied
rivers is negligible, the difference of mean annual
concentration estimation between two methods does
not exceed 20% for cations (Ca, Mg) and 8% for TDS
and TDS_c defined as [Ca2+]+[Mg2+]+[Na+]+[K+]+
[SiO2]+[SO42]+[Fe] and [Ca2+]+[Mg2+]+[Na+]+[K+],
respectively.
The mean multi-year flux of element i (R i ) is
calculated as
Ri 4 ¼ Ci 4dW 4=A;
ð2Þ
where C i * is the multi-year average concentration
of element i calculated as described above and
corrected for atmospheric input according to Négrel
et al. (1993) and Oliva et al. (2003), A is the
watershed area (km2) and W* is the multi-year
average water discharge (km3/year) for considered
period taken from the Hydrological Survey Database (Resources, 1973a,b,c).
The annual suspended matter (SM) fluxes were
taken from the USSR Hydrological Survey database
(Resources, 1973a,b,c). The method of SM flux
230
Table 2
Hydrological parameters of studied rivers and mean multi-annual concentrations
River,
gauging
stations
Area,
km2
Runoff,
mm
Mean
watershed
altitude, m
Years of water
sampling
Mean annual concentration, mg/L
Ca
Mg
Na+K
TDS_ c
SiO2+Fe
1
Balyaga,
Balyaga
Bol. Nimnyr,
Nimnyra
1240
40
984
1971, 1974–1975
29.0F5.8
4.9F3.1
5.3F3.5
39.2F10.7
12.9F0.3
1900
416
1130
7.4
3.5
0.4
11.3
6.6
Bolshaya,
Pokrovskoyea
Bol. Yllymakh,
Yllymakh
193
268
964
9.0
1.4
1.0
11.5
9.7
2710
425
940
9.5F1.1
3.0F0.4
0.1F0.1
12.6F1.6
7.5F0.6
5
Chara, Chara
4150
393
1370
4.8F0.4
0.4F0.1
3.0F0.3
8.1F0.9
6.9F0.1
6
Chikoy,
Gremyachka
Chikoy,
Povorot
15,600
230
1300
7.9F0.7
0.8F0.2
2.1F0.1
10.8F0.9
10.5F0.03
44,700
184
1230
8.4F0.6
0.7F0.2
1.1F0.1
10.2F0.9
12.2F0.3
13.9
2.2
3.0
19.1
9.9
12.9
2.3
1.7
16.9
11.7
4.2
0.1
2.9
7.2
5.7
6.2F1.3
0.4F0.4
1.8F2.0
8.4F3.0
11.7F0.8
2.1F0.1
0.4F0.04
3.5F0.1
6.0F0.3
5.7F0.02
10.9
1.7
0.7
13.3
10.0
9
Hilok,
Khailastuya
38,300
83
1060
10
Hilok,
Maletaa
Ingamakit,
Ingamakita
Konda,
Alkiser
23,700
98
990
1010
500
1040
5350
26
1090
Lurbun,
Lurbun
Maximikha,
Maximikhaa
Murin,
Kharamurina
Timpton,
Ust-Timpton
Turka,
Sobolikha
577
465
1480
444
117
670
1954, 1956–1958,
1960–1962, 1964–1966,
1969–1970, 1975
1955, 1963, 1969,
1971, 1974, 1975
1955, 1958–1960,
1962, 1965–1966,
1969–1970, 1975
1958–1962, 1964–1968,
1970, 1975
1962–1963, 1965,
1969, 1971, 1974–1975
1955, 1958,
1962–1963,
1965, 1969,
1971, 1974–1975
1955, 1958, 1963,
1965, 1969, 1971,
1974–1975
1962, 1969, 1971,
1974–1975
1962–1963,
1965–1966
1963–1965,
1966–1967,
1969–1970, 1975
1962–1963,
1965–1966
1971, 1974–1975
1130
661
1520
1971, 1974–1975
3.9
1.0
0.9
5.8
6.4
43,700
384
1010
4.1F1.2
0.9F0.1
0.1F0.1
5.1F0.5
8.3F0.1
5050
286
1180
1958, 1960–1962,
1966–1967, 1975
1965, 1969,
1971, 1974–1975
7.3F0.4
1.0F0.2
0.7F0.2
9.0F0.8
7.4F0.7
2
3
4
7
11
14
15
16
17
18
19
Na
K
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
No. on
the map
Tzipa,
Baunta
3240
256
1510
21
Viluika,
Selenga
Vitim,
Romanovka
255
418
–
18,200
129
1310
Zhuya,
Svetliya
Olekma,
Kudu-Kel
4790
340
950
115,000
273
860
25
Uchur,
Chulbu
108,000
357
960
26
Vitim,
Bodaibo
186,000
256
–
27
Bol. Amalat,
Ust-Antosea
2100
142
1190
22
23
24
Stations sampled in the present study
8
Chitinka,
2640
90
Burgen
12
Ingoda,
6130
229
Deshulan
13
Ingoda,
12500
157
Uletya
1960, 1962,
1966–1967,
1970, 1975
1971, 1974–1975
1953–1954,
1956–1959,
1966–1967,
1969–1970,
1975
1970–1975/5
1961–1962,
1966,
1969–1970,
1975
1959,
1961–1966,
1970
1950–1951,
1954,
1956–1957,
1960,
1962, 1964,
1966–1967,
1969–1970,
1975
1959–1961,
1964–1966,
1970, 1975
11.3
0.2
1.0
12.5
6.9
9.4F0.5
1.2F0.1
1.5F0.1
12.1F0.8
9.7F0.1
6.2F0.7
0.9F0.2
0.8F0.3
7.9F1.2
7.7F0.6
9.5
0.9
0.2
10.5
4.5
7.0F1.1
1.7F0.3
4.9F1.1
13.7F2.9
11.1F0.7
8.3F0.4
3.6F0.2
0.2F0.04
12.1F0.7
6.2F0.02
6.4F0.4
1.3F0.1
0.1F0.1
7.9F0.6
6.4F0.2
16.6
5.5
5.5
27.6
14.5
1180
1984–1986
7.6F1.1
3.0F0.6
1.6F0.6
12.1F2.2
9.8F1.3
0.89F0.5
0.62F0.08
1630
1983–1986
6.9F0.2
1.3F0.02
1.2F0.1
9.4F0.3
12.5F0.1
0.51F0.03
0.70F0.2
1260
1983–1986
5.9
1.6
2.0
9.5
10.0
1.00
0.98
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
20
a
Because of lack of detailed annual discharge data for these stations, the chemical fluxes (and mean concentrations) were estimated on the basis of single value of mean multiannual Q for period of 1950–1985. The standard deviation does not exceed 30%.
231
232
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
Fig. 3. Water discharge (shaded) and concentration (lines) of cations during the ice-free period on the gauging stations sampled in this
study: r. Chitinka (No. 8) in 1984 (A) and r. Ingoda (No. 12) in 1986 (B). The rivers are frozen to the bottom from December to
March.
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
estimation used by the Hydrological Survey is based
on the time interpolation between the values
measured at the main phases of hydrological regime
and, more frequently, at the rising water level (15–
30 times per year). The suspended matter concentration measurements for the small rivers are scarce
and provided only occasionally. Available data on
SM for the following rivers and the years were used
in this work: r. Chikoy at Gremyachka in 1953–
1967, r. Hilok at Hailastuy in 1948, 1950–1967, r.
Vitim at Bodaibo in 1946–1953, 1957–1961, 1969,
1972, 1974–1975, r. Vitim at Romanovka in 1957–
1958, 1970–1975, r. Olekma at Kudu-Kel in 1967,
1970–1975, r. Chara at Chara in 1962–1970, 1975,
r. Lurbun at Lurbun in 1961–1966, r. Zhuya at
Svetliy in 1970–1975.
233
3. Results
The chemical composition of river waters is
controlled by the hydrological regime and results from
the mixing of rain, snow melting and groundwater
input. Concentrations of major elements vary by a
factor of 2–7 over the annual cycle. Examples of
diurnal discharge and element concentration variations
obtained in the present study are illustrated for
Chitinka River (No. 8, year 1984) and Ingoda river
(No. 12, year 1986) in Fig. 3a and b, respectively.
Typical data of Hydrological Survey are illustrated for
Vitim River (No. 22, year 1965) and Chikoy River
(No. 6, year 1965) in the appendix (Fig. A2a,b). For
most rivers, the total dissolved solid ranges from 20 to
200 mg/L and calcium dominates among cations.
Table 3
Average for the period 1954–1975 chemical and suspended matter (SM) fluxes
No. on the map
River, gauging stations
Flux, tons/km2/year
SM
1
2
3
4
5
6
7
9
10
11
14
15
16
17
18
19
20
21
22
23
24
25
26
27
Balyaga, Balyaga
Bolshoi Nimnyr, Nimnyr
Bolshaya, Pokrovskoye
Bol. Yllymakh, Yllymakh
Chara, Chara
Chikoy, Gremyachka
Chikoy, Povorot
Hilok, Khailastuy
Hilok, Maleta
Ingamakit, Ingamakit
Konda, Alkiser
Lurbun, Lurbun
Maximikha, Maximikha
Murin, Kharamurin
Timpton, Ust-Timpton
Turka, Sobolikha
Tzipa, Baunt
Viluika, Selenga
Vitim, Romanovka
Zhuya, Svetliy
Olekma, Kudu-Kel
Uchur, Chulbu
Vitim, Bodaibo
Bol. Amalat, Ust-Antosea
Stations sampled in the present study
8
Chitinka, Burgen
12
Ingoda, Deshulan
13
Ingoda, Ulety
a
River with dominating basic rocks.
21.1
10.5
3.3
45.8
6.7
21.8
2.6
9.4
Ca
Mg
Na+K
TDS_ c
SiO2+Fe
1.2
3.1
2.4
3.9
2.0
1.7
1.5
1.2
1.3
2.1
0.2
1.0
1.3
2.6
1.6
2.1
2.9
3.9
0.8
3.2
1.9
3.0
1.6
2.4
0.2
1.5
0.4
1.2
0.2
0.2
0.1
0.2
0.2
0.1
0.01
0.2
0.2
0.6
0.3
0.3
0.1
0.5
0.1
0.3
0.5
1.3
0.3
0.8
0.2
0.2
0.3
0.1
1.2
0.5
0.2
0.2
0.2
1.4
0.05
1.6
0.1
0.6
0.03
0.2
0.2
0.6
0.1
0.1
1.4
0.1
0.03
0.8
1.6
4.7
3.1
5.2
3.4
2.3
1.9
1.6
1.6
3.6
0.2
2.8
1.6
3.9
1.9
2.6
3.2
5.0
1.1
3.6
3.8
4.3
2.0
3.9
0.5
2.7
2.6
3.1
2.9
2.3
2.2
0.8
1.1
2.8
0.3
2.7
1.2
4.2
3.2
2.1
1.8
4.0
1.0
1.5
3.1
2.2
1.6
2.1
0.7
1.6
0.9
0.3
0.3
0.3
0.1
0.3
0.3
1.1
2.2
1.5
0.9
2.8
1.6
Na
K
0.08
0.12
0.16
0.06
0.16
0.15
234
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
3.1. Dissolved fluxes of elements
The total dissolved cation flux (TDS_c=[Ca2+]+
Mg2+]+[Na+]+[K+]) of the studied rivers varies from
0.2–14.7 tons/km2/year or 7–151 kmol/km2/year
(Table 3). The flux of [SiO2]+[Fe] varies between 0.2
and 4.2 tons/km2/year, equivalent to up to 30% of total
dissolved cation flux. Minimal TDS_c flux is observed
in the central part of the region for rivers with low
runoff (Konda, No. 14; Chitinka, No. 8; Hilok, Nos. 9–
10). The stack diagram of Ca, Mg, and Na+K fluxes for
studied rivers is presented in Fig. 4.
In accord with measurements of Huh and Edmond
(1999), calcium dominates the cationic flux, accounting for 60–80% of TDS_c value. Magnesium and
sodium+potassium contributions vary between 40%
Fig. 4. Mean multi-annual cationic fluxes for rivers from the studied territory showing the cations contribution to the total dissolved
flux.
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
and 20%. The highest Mg fluxes (e.g., more than 1
tons/km2/year) are observed for the rivers Bolshoi
Nymnyr (No. 2), Bolshoi Yllymkh (No. 4) and
Uchur (No. 25), which can be explained by the
presence of a small proportions (less than 10% by
area) of dolomitic rocks in their watersheds. In
accord with previous studies of crystalline rock
235
(White and Blum, 1995; Oliva et al., 2003), the
rivers of Siberian Craton exhibit a positive correlation between chemical denudation rate and the water
runoff (Fig. 5A) whereas the total dissolved solid
concentration exhibits a flat to slightly negative
sloped relationship with runoff (Fig. 5B). The
majority of cations are removed during the summer
Fig. 5. Dependence of cationic total dissolved fluxes (A) and total cation concentration (B) on mean annual runoff for studied rivers.
Amalat River (No. 27) draining basaltic-bearing terrain falls off the correlation exhibiting twice higher erosion rate for the similar
runoff.
236
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
Fig. 6. Seasonal distribution of cation flux and water flow (numbers
over the columns) for Chikoy River (No. 6) in 1965.
monsoon. The spring flood yields 10–20% of the
annual flux and the winter season accounts for only
5–15% which is illustrated for Chikoy River as an
example (Fig. 6).
3.2. Suspended matter fluxes
Mean annual suspended sediment concentrations
of studied rivers do not exceed 50 g/m3 in the
rivers of Baikal and Vitim uplifts and 25 g/m3 in
the rivers of Aldan and Stanovoy uplifts. Maximal
suspended sediments concentration is usually
observed during snow melt and the monsoon flood
(Resources, 1973a,b,c). Monthly fluxes of suspended matter for two large (Vitim, No. 26;
Olekma, No. 24) and two small (Chara, No. 5;
Ingamakit, No. 11) rivers are shown in Fig. 7. The
Olekma and Vitim rivers exhibit the lowest flux of
SM whereas Chara and Ingamakit have very high
SM flux because the latter drain the Chara
depression filled by terrigenous rocks and granitic
alluvium.
Suspended matter size ranges from 0.01 to 0.14
mm. The fraction 0.01–0.05 mm constitutes 30–
50% of the total flux and the fraction N0.05 mm
represents more than 50%. The contribution of
b0.01 mm fraction is not so important (approximately 10–20%).
For eight rivers, it was possible to make reliable
estimates of annual suspended matter (SM) flux
because sufficient mean monthly data were available. The mean annual values vary from 2.6 to 45.8
tons/km2/year and increase with water runoff.
Temporal variability of physical erosion is greater
than spatial heterogeneity and reflects hydro-meteorological conditions for a given year (Fig. 7). In
spite of mountainous relief and high precipitation
Fig. 7. Mean monthly fluxes of suspended matter for four contrasting rivers of granitic terrain.
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
during short period of time, a number of environmental factors slow down the physical erosion in
the Aldan Craton. Permafrost, forestation and the
presence of soils with sod horizon strongly stabilized by grass roots tend to keep the weathering
products on site. Therefore, any weakening of these
factors favors the removal of solid particles and
rises the SM flux. It is known that permafrost is
very sensitive to warming and over moistening
(Matsuoka, 2001). For example, for some years
(1973 on r. Vitim, 1963 on r. Lurbun), SM flux is
two to four times higher than the multi-year
average. This can be explained by high precipitation
for these years that accelerates solifluction and
releases mudflows.
3.3. Underground input
The main source of cations in rivers is leaching
from soils and rocks by surface and subsurface
waters. We attempted to distinguish between the
fluxes of cations derived from surface and soil
waters and from groundwaters for two rivers of
Amur basin, Chitinka (No. 8) and Ingoda (No. 12),
using results of our field observations. For this, we
used a conventional hydrochemical method (Drozd,
1969; Pisarsky and Khaustov, 1973). This method is
based on the analysis of mixing process and
assumes that (i) two sources have contrasting
concentration of dissolved elements, (ii) on the
flood crest (peak of the snow melt or the monsoon)
the contribution of groundwater is insignificant, and
(iii) the relation between concentration and discharge C=f( Q) (Eq. (1)) for the river is met during
the different flood events. The groundwater discharge
was calculated as
Qgw ¼ Qr ðCr Cs Þ= Cgw Cs
ð3Þ
where Q gw is the discharge of the groundwater for a
given day, C gw is the mean concentration of ith
element in the groundwater assumed being equal to
river water concentration during the low level
period in winter, Q r represents the river discharge
for a given day, C r is the concentration of ith
element in the river for this day, and C s is the
concentration of ith element in the surface waters.
The latter parameter was postulated to be equal to
237
C r during the peak of the flood when the concentration is quasi-constant (Fig. 3). The values C gw
and C s were determined from the State Hydrological Network archive data (Hydrological Yearbooks, 1965–1975) and the field observations of
this study. The uncertainties associated with these
estimations do not exceed 30%.
The Chitinka River is smaller that the Ingoda
River by more than a factor of 2 and also has less
than half as much runoff (Table 2). They have
similar hydrogeological conditions and, according to
this model, exhibit comparable values of groundwater runoff (21 and 22 mm, respectively) and
dissolved cations concentration (Fig. 8). However,
the proportion of surface waters exerts the main
control on total element fluxes: between these two
watersheds, Ingoda exhibits the highest surface
runoff and thus the highest chemical erosion rate.
3.4. Role of lithology
Within the large territory of Precambrian granitogneisses, it is difficult to identify the purely granitic
watersheds; some proportion (i.e., 1–10%) of basic
or carbonate rocks can never be excluded. In order
to reconstruct the different rocks contribution to
total dissolved cation flux for the Siberian Craton,
we used the ratios of Ca and Mg fluxes to those of
Na+K. The chemical composition of rocks was
obtained from Frost et al. (1998), Makrygina and
Fig. 8. Comparison of dissolved fluxes for surface and groundwaters for Chitinka (No. 8) and Ingoda (No. 12) rivers sampled in
this study.
238
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
Petrova (1998), Smelov and Beryozkin (1993), and
Puchtel et al. (1993). It was found that most rivers
bear the signature of granite and gneisses as
parental rocks (Fig. 9). Only six rivers (Chara,
No. 5; Lurbun, No. 15; Ingoda, No. 13; Olekma,
No. 24; Konda, No. 14; Chikoy, No. 6) exhibit the
ratios close to proper granite. Other rivers lay in the
trend from granites to basalts or carbonates and
exhibit the Ca/Mg ratios that are similar or higher
than those of granites. It is known that even in
small granitic watersheds the Ca/Mg ratio in runoff
is normally higher than the ratio in the rocks
(Stallard, 1985) because of the enrichment of Mg
(and K) in the weathered granite due to preferential
retention of micas and K-feldspar during weathering
(White and Brantley, 2003). The rivers Uchur (No.
25), Bolshoi Nimnyr (No. 2), Bolshoi Yllymakh
(No. 4), Timpton (No. 18), Zhuya (No. 23) and
Vitim at Bodaibo (No. 26) have a signature of
carbonate rocks. Indeed, most of the watershed area
of these rivers is underlain by granites and only
close to the gauging stations, the carbonate rocks
appear that represent not more than 5% of the total
watershed area.
4. Discussion
The present study allows estimation of annual
element fluxes based on measurements of high and
low runoff regimes. Moreover, this time (1950–
1975) pertains to a period before the intensive
industrial development of the region. Thus, our
study represents a rigorous quantification of longterm granite weathering in a pristine environment.
The previous investigation of chemical weathering
on the Aldan Craton (Huh and Edmond, 1999) was
based on one-point sampling during the summer. In
Huh and Edmond’s (1999) study, most of sampling
points were located in the low reaches of large
rivers where the contribution of sedimentary rocks
may be important. For comparison, we retained six
common to both studies rivers draining mainly
granitic rocks and having similar locations of
sampling points. As one can see from Fig. 10
for Aldan basin rivers, we obtained higher Ca, Mg
and TDS_c fluxes compared Huh and Edmond’s
(1999) values. For the Chara river, the flux given
by Huh and Edmond (1999) is twice as high as
ours. This can be explained by the presence of
Fig. 9. Plot of Mg/Na+K vs. Ca/Na+K molar ratios for studied rivers corrected for atmospheric precipitation, the rainwater and various rocks
composition of the region. The Amalat River draining basaltic rocks is highlighted. Six rivers bearing clear signature of carbonate rocks are
encircled.
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
239
Fig. 10. Annual cationic fluxes for six Aldan Shield rivers reported by Huh and Edmond, 1999 (one point summer measurements, dark columns)
and those assessed in this study (mean multi-annual values, light columns).
carbonate rocks in the low reaches of Chara River
sampled by Huh and Edmond (1999). Besides, one
should keep in mind the possible change of river
water composition in Chara region due to the
impact of industrial activity from the beginning of
1970s. The differences for the other rivers stem
from the difference in methods of flux calculation:
multi-annual (our data) and one-point sampling
(Huh and Edmond, 1999). Note that the summer
concentrations of Ca, Mg and TDS_c measured by
Huh and Edmond (1999) in Bol. Nymnyr (No. 2),
Bol. Yllymakh (No. 4), Uchur (No. 25) and
Timpton (No. 18) are comparable with those of
the Hydrological Survey for the same period of the
year (not shown). However, for annual values, an
underestimation of fluxes by Huh and Edmond
(1999) is possible which is caused by underestimation of water runoff values taken from
UNESCO maps in their study. It is known that
the hydrological maps describe with good accuracy
the latitudinal hydrometeorological characteristics.
However, in mountain regions where the runoff
strongly depends on the altitude, these maps cannot
properly reproduce the flux and their use should be
avoided.
From previous studies of granites chemical
weathering (White and Blum, 1995; Oliva et al.,
2003), it is known that cationic and Si fluxes
strongly depend on water runoff and mean annual
temperature. When compared to other cold and
240
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
temperate regions of the world, it is seen that the
overall chemical erosion (TDS_c flux) on the Aldan
Craton is higher than it is expected from a general
correlation between element fluxes and water runoff
in granitic environment (Fig. 11A). Calcium flux
provides the major contribution to the elevated
TDS_c values (Fig. 11B) while the fluxes of Mg
(Fig. 11C) and Na+K (Fig. 11D) are comparable to
those of cold environments at similar runoff values.
The SiO2 fluxes of Aldan rivers are well correlated
with water runoff (Fig. 12) and lay in the trend for
arctic and glacial environments (Anderson et al.,
1997, 2000; Oliva et al., 2003).
It has been argued that in modern alpine glacial
environments, the cation denudation rate is greater
than that in granito-gneisses metamorphic watersheds of plains and is a little lower than that in
basaltic terrain (Oliva et al., 2003). Among the
factors that are responsible for enhanced weathering
in granitic environments, rapid dissolution of
carbonate traces (White et al., 1999b), Ca-plagioclases (Oliva et al., 2004), biotite and grinding of
rocks exposing fresh mineral surfaces (Anderson et
al., 1997) have been suggested. In the permafrost
region, another important factor of weathering can
be the frost mixing within soil profile which
supply the upper reactive horizons by fresh
minerals (Ershov, 1995). For example, freezing
front migration downwards leads to irreversible
changes in the soil structure and to transformation
Fig. 11. Plot of cationic TDS_c (A), calcium (B), magnesium (C), and Na+K (D) mean multi-annual fluxes calculated over 1950–1975
period as a function of runoff for various granitic watersheds of Siberian Craton (open circles). The data for cold (TV5 8C), temperate
(5 8CbTV13 8C) and permafrost-bearing watersheds are from the database of Oliva et al. (2003). Data for glacial watersheds are from
Oliva et al. (2003) and Anderson et al. (1997).
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
241
100
Siberia
cold
temperate
glacial
permafrost
Flux SiO2, t/km2/y
10
1
0,1
0,01
10
100
1000
10000
runoff,mm
Fig. 12. SiO2 flux as a function of runoff for cold (TV5 8C), temperate (5 8CbTV13 8C), permafrost-bearing and glacial regions (Anderson
et al., 1997; Oliva et al., 2003) compared to Siberian Craton (mean multi-annual values, this study).
and neoformation of clay minerals within the active
layer as it was shown for Transbaikal region (Vogt
and Larqué, 1998) and Kolyma Lowland (Alekseev
et al., 2003). Numerous experimental and field
studies under soil freezing/thawing conditions have
evidenced (i) accelerated minerals transformation
and weathering (Zvereva and Ignatenko, 1983;
Konishchev and Rogov, 1993; Polubesova et al.,
1996), (ii) soil acidification and increase of cation
fluxes (Fitzhugh et al., 2003 and references therein)
and (iii) non-stoichiometric mineral dissolution
induced by mechanical disaggregation by freeze–
thaw cycles (Hoch et al., 1999; Hall et al., 2002).
Therefore, mechanical exposure of fresh surfaces
by frost shattering may hinder any negative
temperature effect on rock weathering in cold
climate. This led Huh and Edmond (1999) to the
conclusion that there is no discernible climatic
influence on weathering on regional scales.
Another important weathering factor in South
Siberia is vegetation. In contrast to glaciated alpine
environment covered by poor vegetation or by
coniferous trees (fir, pine) and arctic regions with
tundra vegetation (Canada), the larch trees of
Central Siberia provide important annual supply of
litter which is likely to degrade fast in O horizon
producing highly reactive organic ligands (Targulian, 1971). Because the weight proportion of Ca in
moss, lichens and whole tree biomass is at least five
times higher than that of Mg (Kovda, 1956), the fluids
of surficial soil horizons become enriched in Ca vs.
Mg (Belousova, 1974). Therefore it is possible that
the fast degradation of litter from deciduous larch
trees can be another factor accelerating the weathering
over the annual cycle compared to the regions with
similar vegetation density dominated by evergreen
trees.
Important role of dissolved organic matter on
global rates of silicate rocks weathering under
boreal conditions has been recently demonstrated
by Millot et al. (2003). Such an effect is consistent
with the results obtained by Moulton and Berner
(1998) and Moulton et al. (2000) for basalt weathering in Iceland, where chemical denudation fluxes
were found to be several times higher in vegetated
areas than in bare rock areas.
242
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
Fig. 13. Annual calcium and silica fluxes together with those of organic matter (PO=permanganate oxidation in tons of oxygen) for four rivers of
studied region.
Following this track, we plotted the annual
calcium and silica fluxes together with that of
organic matter, expressed as permanganate oxidation (PO) in tons of oxygen per km2 (Fig. 13).
Because of paucity of available information, the
annual PO fluxes could be rigorously estimated
only for four rivers having similar runoff values
(100–200 mm/year). For these rivers, a clear
positive correlation between the fluxes of PO and
that of Ca and Si is observed, suggesting important
role of organic matter in element mobilization from
the rocks.
An interesting comparison of Late Proterozoic
and Precambrian granitoids and metamorphic rocks
weathering under similar climatic conditions is
possible, thanks to recent study performed by
Millot et al. (2002) on Canadian Shield. For Slave
and Greenville Provinces having mean annual
temperature of 4 to 4.5 8C, respectively, these
authors reported the TDS_c fluxes of 0.35 and 1.55
tons/km2/year, respectively. For these territories, the
mean runoff varies from 100 mm/year (Slave
Province) to 575 mm/year (Greenville Province).
The Aldan Shield rivers of similar runoff and
temperatures exhibit ca. ~3–4 times higher TDC_ c
values. Several factors may be responsible for this
difference: (i) The density of vegetation and the
depth of soil in the Slave Province (tundra and
subarctic forest) are lower than those in the
Siberian taiga; (ii) the mean annual precipitation
in Slave Province is 350 mm/year which is at least
half that in Siberian Craton; (iii) the temperature at
the time of maximal runoff and maximal transport
of solutes is much higher in Siberia (summer
monsoon at highest annual temperatures) compared
to Canada (spring snowmelt); (iv) high mountain
relief in Siberia, in comparison with Canada Plain,
implies stronger physical erosion via the exposure
of fresh minerals and totally different water flow
paths. However, results of our study do not allow
distinguishing between these processes and further
work in necessary to resolve these issues.
It has been shown in earlier studies (Dunne, 1978;
Bluth and Kump, 1994; Gaillardet et al., 1997; Millot et
al., 2002) that a positive correlation between physical
and chemical erosion rates is a typical feature of
weathering process in various climatic and geological
conditions. Results of Hydrological Survey of South
Siberia presented in this study corroborate this finding
as illustrated in Fig. 14. Similar to other granitic
watersheds of the world, both mean multi-annual
suspended and dissolved load concentrations (Fig.
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
Fig. 14. Correlation between suspended and dissolved load
concentration (A) and fluxes of chemical and physical weathering
(B). Suspended matter fluxes and concentrations represent mean
estimations for a period of 8 years and have an uncertainty of 20–
30%. The data for granitic watersheds of Siberian rivers are in good
agreement with other world data from Millot et al. (2002).
243
with those of temperate regions. Among cations,
calcium is largely responsible for elevated chemical
erosion intensity, in accord with previous study of Huh
and Edmond (1999) for this region. The fluxes of Mg,
Na and K are comparable with those for other granitic
regions of the world.
It has been shown that the complex of natural
conditions formed under specific climate is responsible for extremely high variability of chemical
erosion rates on granitic rocks (Oliva et al., 2003).
In the case of Aldan Craton, the cold and humid
climate provides actively forming soils. Elevated
temperature during the summer leads to relatively
high for permafrost regions vegetation productivity
and provides rapid litter degradation. This can
increase the weathering flux via (i) primary and
secondary minerals dissolution by reactive organic
ligands and (ii) direct release of biogenic elements
such as calcium from the litter in upper soil
horizons. Prevailing of rain on snow precipitation
during the second part of warm period leads to
intensive cycling and removal of mineral grains
which is further promoted by intensive frost mixing
within the soil profile. Therefore, in accord with the
track developed by Millot et al. (2003) for sedimentary rocks weathering in the Mackenzie River
region, we can conclude from the study of Siberian
Craton that although the low temperatures inhibit
chemical weathering reactions, the interlinked factors
such as heterogeneous lithology, soil and dissolved
organic matter, mechanical erosion and freeze–thaw
cycling are able to counteract the negative effect of
temperature and accelerate weathering fluxes.
Acknowledgements
14a) and physical and chemical erosion rates (Fig. 14b)
are positively correlated.
5. Conclusions
Chemical weathering of granitoid rocks in Southern
Siberia was studied based on long-term seasonal
measurements of solute and suspended matter fluxes
for 27 watersheds of various size. The total dissolved
cationic fluxes from this territory are higher than
expected for such cold environment and comparable
The manuscript was greatly improved by insightful
and constructive reviews of S.P. Anderson, J.I. Drever
and R. Yuretich. The authors are grateful to J.
Gaillardet, J. Viers and P. Oliva for useful discussions
in the course of this study. We thank the staff of
Department of Hydrology of Moscow State University
for their continuing help and assistance in providing the
bibliographic information. This work was supported by
the French program PNSE (Program National bSol et
ErosionQ) jointly funded by INSU/CNRS agencies.
[LW]
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E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
Appendix A
Fig. A1. Examples of the relation between concentrations and discharge. Ca=filled circles, Mg=open circles, TDS_c=filled squares, TDS=open
squares, Na=filled diamonds, K=open diamonds.
Table A1
The range of k and n parameters of Eq. (1) for all studied rivers
n
k
Ca
Mg
Na+K
TDS
TDS_c
Na
K
0.1 to 0.47
6–69
0.1 to 0.51
3–37
0.2 to 0.5
7–15
0.1 to 0.4
22–107
0.1 to 0.9
15–96
0.18 to 0.2
2–4
0.17 to 0.25
1.3–1.4
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
245
Fig. A2. Seasonal variation of discharge (shaded) and cations concentration in the Vitim river (No. 22) in 1954 (A) and the Chikoy river (No. 6)
in 1965 (B). Original data are from The Hydrological Survey (Hydrological Yearbooks).
246
E.A. Zakharova et al. / Chemical Geology 214 (2005) 223–248
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