Vol.3, No.7, 517-529 (2011) Natural Science
http://dx.doi.org/10.4236/ns.2011.37073
The relationship of mineral and geochemical
composition to artificial radionuclide partitioning in
Yenisei river sediments dow nstream from
mining-and-chemical combine Rosatom
Bondareva Lydia1, Artamonova Svetlana2
1Institute of Nonferrous Metals and Materials, Siberian Federal University, Krasnoyarsk, Russia;
*Corresponding Author:
2Institute of Geology and Mineralogy SB RAS, Novosibirsk, Russia.
Received 9 December 2010; revised 20 February 2011; accepted 4 March 2011.
ABSTRACT
Discharges from the Mining-and-Chemical Com-
bine (MCC) of Rosatom, downstream from Kra-
snoyarsk-26, near of the Krasnoyarsk resulted
in radioactive contamination of sediments of the
River Yenisei. The concentration of artificial
gamma-emitting radionuclides (137Cs, 60Co, 152Eu,
and 241Am) was determined to analyze the mi-
gration processes leading to the transport of
these radionuclides. The concentration of artifi-
cial radionuclides in the surface layers of the
studied area varied in wide ranges: 137Cs – 318 -
1800 Bq/kg, 60Co – 87 - 720 Bq/kg, 152Eu – 12 -
287 Bq/kg and 241Am – 6 - 76 Bq/kg. There was a
sequence of migration of radionuclides inves-
tigated in the surface layer of sediments that
were collected in the near zone of influence of
the MCC: 241Am ≈ 152Eu > 60Co > 137Cs. Radionu-
clide species have been found to be directly
related to sediment structure and composition.
Keywords: Geochemical Properties; Sediments;
Radionuclides; Correlation; the Yenisei River
1. INTRODUCTION
Earth’s ecosystems, including aquatic ones, have ac-
cumulated large amounts of artificial radionuclides. Ra-
dioactive contamination of river ecosystems presents a
challenge to many European countries. The Yenisei Riv-
er is one of the environments affected by the conti- nu-
ous radioactive contamination. The floodplain soils,
sediments, aquatic plants, and water of the Yenisei River
have been found to contain various artificial radionu-
clides, both activation products and ones produced at the
radiochemical plant of the Mining-and-Chemical Com-
bine (MCC) of Rosatom [1-3]. There is a Mining and
Chemical Combine of Rosatom (MCC) on the left bank
of the Yenisei, 50 km downstream from Krasnoyarsk.
MCC includes radiochemical facilities and nuclear reac-
tors. The production facilities of the plant are located on
both banks of the River Yenisei and connected by a tun-
nel under the river bed. Since 1958 MCC has used water
for cooling industrial reactors to produce weapon-grade -
238Pu. The river water after passing through the cooling
system of the reactors has been brought back to the Riv-
er Yenisei. Two once-through reactors were taken out of
service in 1992, therefore, the reactivity level in the ef-
fluents discharged from the MCC area decreased. The
last reactor with a closed circuit which is to be stopped
in 2010 has been operating till now.
The composition of soils and bottom sediments is
quite complex. Mineral particles of the bottom sediments
are formed in the following way: a positively charged
surface of a mineral particle is surrounded by negatively
charged particles of iron hydroxide, aluminum hydrox-
ide etc, where negatively charged silicic acid and organic
colloids are further adsorbed. Besides particles of dif-
ferent minerals (carbonates, silicates, nitrates, chlorides
etc.) the bottom sediments include the organic constitu-
ent: humic and fulvic acids, individual organic sub-
stances (aminoacids, polysaccharose etc.), metal-organic
and organic-mineral complexes [4]. The moiety of or-
ganic substance dissolving in alkali, but deposited by
acids (рН = 1), was named humic acid (its content in the
soil being up to 70%). The moiety dissoluble both in
acids and alkalies – is fulvic acid; and the one insoluble
both in acids and alkalies is humic acid. Humus sub-
stances are amorphous polyelectrolytes with a wide
range of molecular weights―up to 1000 for the fulvic
acids, 100 - 5*105 for the humic acids (according to
some evidence, up to 106). It has been shown that these
fractions include both aromatic and aliphatic compo-

B. Lydia et al. / Natural Science 3 (2011) 517-529 518
nents; their main building blocks are complex phenolic
and benzene-carboxyl structures. These acids are closely
interconnected and can transfer into each other. They are
complex-formers and, consequently, metals in soils and
bottom sediments can be in the form of soluble or in-
soluble complexes with humic and fulvic acids [4].
It is known that radionuclides are associated with
bottom sediments. The mechanisms of the radionuclide
fixation in the mineral phase of the soil may be different:
reversible physical absorption, chemosorption (reversi-
ble and irreversible), introduction into the crystal lattice
of the minerals or exchange for the cations located on
the surface of the mineral particle. Here, radioisotopes
may be: 1) in pore solutions of the bottom sediments in
the form of ions, organic and inorganic complexes, 2) on
the particles of the bottom sediments in cation-exchange
form; also they may be more tightly connected due to the
sorption, co-deposited with the oxides of other elements
(for example, with Fe, Mn oxides), included in the bio-
mass of dead plants and microorganisms, as well as in-
cluded in the structures of the primary and secondary
minerals of the bottom sediments. In spite of the variety
of the existence forms all the substances present in the
bottom sediment mass participate to a greater or lesser
extent in the migration processes including also dissolv-
ing-sedimentation, absorption-desorption, diffusion of a
chemical gradient and diffusion into the micropores of
the mineral particles. Consequently, the migration prob-
lem of the physical and chemical forms of substances in
the bottom sediments is important for understanding
how mineral and geochemical peculiarities of the bottom
sediments influence the geochemical cycles of a water
reservoir.
The diversity of migration flows and different forms
of substance transport can be characterized by two main
vectors: biogenic and abiotic. The abiotic flow is differ-
entiated into vertical descending, vertical ascending,
inter-horizontal (diffuse), lateral, and surface (erosive)
sub-flows, and the sub-flow inside the sediment layer.
The contribution of a sub-flow into the total migration
flow is determined by the degree of heterogeneity and
polydispersity of the sediment. Thus, description of the
migration should be based on studies of both substance
transfer (percolation, diffusion, dispersion, etc.) and ac-
cumulation (particle sedimentation, mineral formation,
sorption, etc.) [5].
To investigate the forms of existence and migration
ability of radionuclides as well as that of metals different
methods of the sequential chemical fractionation are
used. According to the recommendations of the Interna-
tional Union of Pure and Applied Chemistry (IUPAC),
sequential extraction of the element forms from the soils,
silts and bottom sediments is attributed to the methods of
the element fractionation [6]. The main principle of such
fractionation implies that every sequential leaching re-
agent must be either stronger by its chemical action than
the previous one or it must be of a different nature. It is
possible to distinguish at least 8 different fractions of
heavy metals, including radionuclides. It is worth noting
that the fractionation is not associated with the extraction
of individual chemical compounds but with the extrac-
tion of their assembly. Each fraction extracted under the
action of a particular leaching reagent, as a rule, turns
out to include a group of compounds possessing similar
properties (namely, physical and chemical mobility and
bioavailability). In general the results of the fractionation
of the element forms depend on the reagents used, con-
tact time of the liquid and solid phases, intensity of
shaking the mixture, ratio of the sample weight to re-
agent amount and peculiarities of the soils and bottom
sediments under investigation.
Washing the sample with water and solution of some
electrolyte is aimed at establishing the content of readily
soluble and exchange forms of radionuclides in the sam-
ple. However, after several tens of years of their entering
the atmosphere, radionuclides could have coupled stro-
ngly in partially soluble and insoluble forms. Exchange
and readily soluble forms of radionuclide existence are
of interest since, firstly, some of them may be destroyed
by plant roots, resulting in penetration into the food
chains; secondly, during spring floods and other natural
events the bottom sediments can move down the river
stream, leading to the contamination of areas located
down the river as far as the estuary of the river and the
ocean.
The most frequently mentioned chemical compounds
being present in the soils and bottom sediments are car-
bonates, sesquioxides and hydroxides, organic substances
and clay minerals. Here, carbonates can be destroyed by
an acid solution, however, this may be accompanied by
the destruction of other fractions, therefore, at present
carbonates are destroyed using subacid solution of so-
dium or ammonium acetate (рН = 5, which is achieved
using nitric or acetic acid) [7-9]. Sesquioxides and hy-
droxides are destroyed when interacting with acid solu-
tions, though quite diluted ones, since using concen-
trated acids may result in solving other fractions. For рН
of the solution to change only slightly in the interaction
process, the salt of this acid is added into the acid to cre-
ate the buffer effect. Tamm’s solution has long been used
which is an ethanediodic acid solution with ammonium
oxalate [10,11]. At present the solution of hydroxyl-
amine chloride in acetic acid is also used [6-8,12]. To
destroy the organic substance use is usually made of the
following oxidizing components: hydrogen peroxide
[11,12], alkali pyrophosphates [8,12,13]. Amorphous

B. Lydia et al. / Natural Science 3 (2011) 517-529 519
silicates are destroyed by the solution of potassium or
sodium hydroxide solutions [11].
When comparing the results obtained in the analysis
using most of the techniques it is possible to partly de-
scribe the type of the compounds formed and only with
great approximation. Since a particular fraction may
imply quite a wide range of compounds (movable or
soluble in acids [10]) or a reagent is chosen which has an
application limited by the frame of the objects under
investigation (sodium pyrophosphate is convenient for
studying light soils with a small amount of sand or for
studying suspensions) [12].
The method of sequential chemical fractionation has
the following shortcomings: 1) insufficient flexibility,
low selectivity of the reagents used relative to the ex-
tracted forms of the elements (soluble mineral phases of
the sample) and, consequently, poor reproducibility of
the results obtained [14]; 2) it takes several days of rou-
tine work since the extraction of the element forms from
the solid samples in static conditions (without renewing
the reagent solutions) is slow. Consequently, estimating
the flexibility and bioavailability of the element forms
may not always be correct because the processes in nat-
ural conditions always occur in dynamics, i.e. with con-
stant renewing of the reaction soil solution.
In spite of the shortcomings of the chemical fractiona-
tion method it is frequently used, since being rather sim-
ple it enables one to obtain important information. And
the results obtained using sequential chemical fractiona-
tion allows one to make preliminary forecasts on the
possible migration of the radionuclides.
The purpose of this study was to determine the rela-
tionship between the mobility of artificial radionuclides
and the mineral and geochemical properties of the Yeni-
sei River sediments in the areas immediately affected by
the operation of the MCC.
2. MATERIAL AND METHODS
2.1. Study Area. Material
A great part of the population of the Krasnoyarsk Re-
gion lives on the banks of the River Yenisei. The Yenisei
is one of the biggest rivers in the world: its longitude
from the conflux of the Big Yenisei and Little Yenisei to
the Kara Sea is 3487 km (from the headstreams of the
Little Yenisei—4287 km, from the headstreams of the
Big Yenisei—4123 km). The conflux of the Big and Lit-
tle Yenisei, near the town Kyzyl is considered to be the
geographical center of Asia. Starting in the south of in
the mountain deserts of Mongolia the River Yenisei over
almost 3000 km flows to the north across different lati-
tudinal geographical zones and inflows into the Arctic
Ocean, forming an estuary up to 30 km wide. The
length is bigger than that of the rivers Danube (2857 km);
Mississippi (3770 km); Indus (3180 km). The Yenisei is
the most full-flowing river of Russia with an annual wa-
tershed yield 624 km3. The average water discharge in
the estuary is 19800 m³/sec, the maximal one up to -
190000 m³/sec. As to the basin area (2580 thousand km2)
the Yenisei is the second river in Russia (after the river
Ob) and the seventh in the world. The River Yenisei is
the nominal boundary between the West and East Siberia.
There are three hydroelectric power stations on the Ye-
nisei and tributaries. The river water is highly transpar-
ent (up to 3 meters) and has low mineralization (the
mean value is 54 mg/l) as well as high oxygen concen-
tration. The flow speed and the river width vary signifi-
cantly: from 1.5 to 12 - 15 km/h and from 0.2 - 0.5 km to
3 - 5 km. In the upper reaches of the river bed there are
glacial boulder beds and cobble deposits which in the
middle reach change into sandy gravel and sandy-clayish
ones in the lower current of the river near the inflow into
the Arctic Ocean.
The operation of the greatest hydropower stations re-
sults in constant mixing of water layers. Due to this, at a
big distance down from the hydropower station the water
temperature almost doesn’t change with the depth of the
water flow. In early July the water temperature in the
area near the Krasnoyarsk city and 100 - 150 km down-
stream is ~10℃, and in the late July-August 15 - 17℃.
The river ecosystem is an oligotrophic one with rich
river fauna, there being more than 500 species of algae
and diatoms [15].
Sediments were collected in the area immediately af-
fected by the MCC operation, and samples of their up-
permost layers (0 - 10 cm) were used in the study (Sam-
ples 1 - 5) (Figure 1).
2.2. Sample Preparation
2.2.1. Geochemical Examination
The ground sample was pressed into tablets with di-
ameter 6 mm, mass 30 mg and subjected to synchrotron
radiation X-ray fluorescence analysis (SXRF). Sediment
texture analysis was performed using a hydrometer me-
thod [16] after the destruction of organic matter with
hydrogen peroxide (35%). The particle size analysis of
silty sand is based on the fact that particles of different
sizes have different free-fall velocities and, thus, they
settle onto the bottom within different time periods. The
suspension with the yet unsettled particles was repeat-
edly decanted off at certain time intervals to separate
fractions of <0.05-mm and <0.01-mm particles. The
<0.05-mm fraction was separated by decanting off 6 cm
of the suspension in 30 sec after the mixture was pre-
pared and the <0.01-mm fraction by decanting off 2 cm

B. Lydia et al. / Natural Science 3 (2011) 517-529 520
Figure 1. Sketch-map of the south of the Krasnoyarsk Ter-
ritory near the Mining-and Chemical Combine (MCC) of
the Rosatom (Zheleznogorsk). “0 km”—place of industrial
effluent water MCC; “15 km”—distant frontier region dis-
card samples.
of the suspension in 4 min. The separated suspensions
were dried at 105˚C. The heavy mineral fraction was
recovered from the sand fraction using tribrommethane
(СНВr3) of the density 2.899 g/cm3 at 15˚C: quartz of
the density 2.651 - 2.68 g/cm3 and feldspars of the den-
sity 2.54 - 2.75 g/cm3 floated to its surface.
2.2.2. Differential Thermogravimetric Analysis
For determining some components of the bottom sedi-
ments (pore water, organic substances, carbonates, water
incorporated into the layers of the clay minerals) the me-
thod of the differential thermogravimetric analysis was
used [17].
The portions of the naturally wet sediment samples
under study (1 g) were placed into a porcelain crucible.
Previously, the weight of the crucible had reached the
constant value after burning in a muffle oven at 500˚C,
for 3 days. The crucible with the bottom sediment sam-
ple was placed into the muffle oven. At 105˚C the cruci-
ble weight with the sample portion was also brought to a
constant value during 48 h. In such a case there appeared
water which could be attributed to pore (adsorption) wa-
ter. After determining the adsorption water content in the
sample the crucible with the portion was put into the
muffle oven where it was heated at 350˚C, for 16 hours.
In this case СО2 was released which had formed at the
decomposition of the organic substances present in the
bottom sediment samples. The water included into the
interlayer space of the clay minerals and clays (incorpo-
rated H2O), was determined at the subsequent sample
heating at 600˚C, for 8 - 9 hours. When increasing the
burning temperature up to 850˚C the sample weight loss
was caused by the release of СО2, formed in the process
of the thermal decomposition of the carbonates. In all the
cases the samples were weighed only after cooling down
to room temperature the crucible with the bottom sedi-
ment sample in an exsiccator. The error of the differen-
tial thermogravimetric method was less than 10%.
The calculation of the content of organic substances in
the bottom sediment samples was made using formula
[18]:
0.458 0.4yx


where y is the amount of the organic substance, mg; х is
the weight decrease after burning at 350˚C, mg.
2.2.3. Sequential Chemical Extraction
The total weight of the samples taken was 5 kg. Im-
mediately after sampling the whole amount of the sub-
stance was sieved with the mesh diameter being 0.5 μm
and divided into several portions with the weight ap-
proximately 1 kg. Each portion was packed into a plastic
bag and placed into a fridge. Just before carrying out
sequential chemical fractionation the bottom sediments
from the bags were thoroughly mixed. From the whole
amount the portions having 80 g of wet weight were taken.
For each fractionation scheme 3 portions were selected.
The literature data analysis has shown that the tech-
nique of fractional extraction of the radionuclides from
the soil includes several variants. All the existing tech-
niques are based on the destruction of the constituents of
the soils with the subsequent extraction of the radionu-
clides included into a particular form.
Two of the most widely spread schemes of sequential
chemical fractionation were used in the work. This is
fractionation developed on the basis of the Tessier tech-
nique [11,19,20] and a scheme developed by the Com-
munity Bureau of Reference (BCR) [21,22]. Table 1
presents both schemes used in our investigations of the
existence forms of artificial radionuclides in the bottom
sediment samples of the River Yenisei (Table 1).
The remaining residue mainly consisted of clay min-
erals, feldspars and quartz. The percentage of extraction
in each step was determined as the ratio of the nuclide
activity in the extract and its initial activity in the sedi-
ment sample. In some cases the radionuclide activities in
the extract were below the minimum detectable activity
(MDA). For the calculation of the non-extracted residual
fraction we have used (MDA/2 ± MDA/2)% as a, ficti-
tious” value (recommendation by ISO Working Group
TC85/WG17).
2.3. Measurement Procedures
The silicate composition of sediment samples was de-

B. Lydia et al. / Natural Science 3 (2011) 517-529 521
Table 1. Used the schemes of the sequential chemical fractionation.
I scheme II scheme
fraction Chemical reagents Phases with Target Ions fractionChemical reagents Phases with Target Ions
I 1 M CH3COONH4 “Exchangeable Ions” 0.11 М
CH3COOH
“Soluble species, carbonates,
cation exchange forms”
II 1 М CH3COONH4
HNO3 up to рН 5
“Carbonates” + “Amor-
phous minerals I
0.5 M NH2OH*HCl,
рН 1.5 “Oxyhydroxides Fe, Mn”
III 0.1 M NH2OH*HCl
in 25% CH3COOH
“Oxides and Hydroxides of
Iron and Manganese” III H2O2, 1 M CH3COONH4 pH 2 “Organic matter, sulphides”
IV H2O2+ HNO3
up to рН 1.5
“Organic Matter” +
“Particles” IV “Residuals”
V 0.1М NaOH “Amorphous Silicates”
VI “Residuals”
termined using a VRA-20R X-ray phase analyzer. For all
determined elements detection limits were 0.02% -
0.005%. Concentrations were calculated using the fun-
damental parameter method [23].
As a sample comparison was used by the standard
“SRS-1A” (RF). To perform the analysis we have con-
ducted measurements of two standard samples of “SG-
1A” (albitized granite) (RF) and “SG-1T” (trapp) (RF)
containing (mass %): SiO2 – 73.36 and 49.12, TiO2 –
0.07 and 1.85, Al2O3 – 13.84 and 14.23, Fe2O3 – 2.16
and 15.31, MnO – 0.19 and 0.21, MgO – 0.05 and 5.74,
CaO – 0.14 and 10.20, Na2O – 5.46 and 2.49, K2O –
4.14 and 0.69 in “SG-1A” and “SG-1T”, respectively.
The trace element composition of sediments was
quantified by the SXRF method. Measurements were
performed using monochromatized primary ray. K, Ca,
Ti, Mn, Fe and 19 trace elements were determined at 23
KeV; Ag, Cd, Sn, Sb, and I were determined at 63.5 KeV.
Bi, Tl, and Hg were estimated from the PbLβ1 calibration
curve, and Te from the SbKά calibration curve. The in-
tensity of secondary radiation was ~ 10000 cps, the ex-
posure time 300 sec. Standard reference material was
Lake Baikal sediment BIL-1. The relative standard de-
viation in determination of concentrations of the ele-
ments listed above was 10% - 15%.
X-ray structure analysis of mineral particles was per-
formed on a DRON-3M powder diffractometer (Russia),
with СuК1 radiation, the tube voltage U = 40 kV, and the
current I = 24 mA. This method was used to qualita-
tively evaluate mass fractions of minerals. The clay frac-
tion of the sediments was impregnated with ethylene
glycol and examined additionally.
The morphology and material composition of total se-
diment particles, the sand fraction, and heavy minerals
of the sand fraction were examined using the electron
scanning microscope ТМ-1000 (Hitachi, Japan), with the
X-ray spectral energy-dispersive analyzer SwiftED (Ox-
ford Instrument Analytical, England) when registering in
back-scattered electrons with the accelerating power of
15 kW in the low vacuum regime. The sediment particles
were directly fixed on the filters by a double-sided adhe-
sive conductive carbon tape on the sample mount and
were placed into the chamber of the electron microscope.
Micrographs scanned in back-scattered electrons were
collected into a separate file and were subjected to stan-
dard digital processing to increase the image sharpness
and contrast. Spectral analysis of some parts of the sam-
ple (selected particles, characteristic details) was made.
Solutions and residual solids resulting from sequential
chemical extraction were analyzed for gamma-emitting
radionuclides on a Canberra gamma-spectrometer (USA)
coupled to a hyperpure germanium (HPGe) detector.
3. RESULTS AND DISCUSSION
Bottom and alluvial sediments are the main depots of
artificial radionuclides released to the Yenisei as a result
of 50 years of MCC operation. The analysis of 5 sedi-
ment cores collected between 5 km and 15 km down-
stream the reactors will be discussed with respect to
137Cs (half-life 30.1 y, fission product), 152Eu (13.5 y,
activation and fission product) , and 60Co (5.3 y, activa-
tion product), which are long lived artificial radionu-
clides discharged to the river water in significant
amounts. According to Vakulovsky [24], in the period
1975-2002 the total discharges from MCC to the Yenisei
amounted to 30.7 TBq and 32.8 TBq for 137Cs and 60Co,
respectively, and 2.7 TBq for 152Eu for the period
1987-2002. In addition, 241Am is a radionuclide of inter-
est due to its long half-life (432.2 y) and its origin in
sediment samples: It was partly released with radioactive
waste discharges but it is also produced within sediments
as a decay product of 241Pu. Moreover, there are just a
few publications reporting on 241Am contamination lev-
els in sediment [3,17].
3.1. Investigation of Geochemical
Properties of the Top Sediment Layers
Sediment samples were analyzed to examine their
grain-size, mineral, and elemental composition. The or-

B. Lydia et al. / Natural Science 3 (2011) 517-529 522
ganic matter was mainly represented by fine dark-brown
detritus and contained considerable amounts of humic
substances [17]. Organic particles adhere to particles of
clay minerals and sand. Therefore, to separate the clay
fraction, we increased the soaking time and the number
of stirrings. Yet, we failed to completely separate organ-
ics from clay minerals. Organics was successfully re-
moved by heating the samples at 480˚C, but the structure
of clay particles had changed considerably. Sediment
samples contained frustules of diatomic algae (Figure 2),
which accumulate high concentrations of radionuclides
and metals [25].
Most of the inorganic components of sediments were
minerals corresponding to acid rocks: fragments of well-
crystallized quartz constituted the largest portion; amounts
of plagioclases and amphiboles were somewhat lower;
the portion of chlorites was small; and the amount of
potash feldspar was insignificant. Micas, gypsum, dolo-
mite, magnesite, carbonates, and clay minerals were
present as minor components, and there were trace
amounts of siderite. Iron minerals were identified as
hematite, and some of them also contained pyrite and
magnetite.
The major fractions of the inorganic component of the
sediment were fine sand (0.25 - 0.05 mm), fine-grained
siltstone (0.05 - 0.005 mm), and fine mineral powder
(<0.005 mm). The 0.004—0.005-mm size range can
include both the smallest of the grains and the largest of
the powder particles. The major grain-size fraction of the
sediments was fine-grained siltstone: 58% to 90%. The
clay fraction made up just ~3%. X-ray diffractometry
showed that the clay fraction consisted of fine powders
of illite, mixed-layered illite/smectite, smectite with kao-
lin inclusions, and chlorite particles, which were much
better crystallized. The fine sand and siltstone fractions
mainly consisted of quartz (up to 60%), as the most sta-
ble component of towards soil formation and weathering
processes, plagioclase (up to 35%), and other detrital
minerals—feldspars, micas, etc. The amounts of heavy
metals and radionuclides contained in the fine sand frac-
tion are usually considered to be insignificantly low. The
fine powder fraction consists of minerals with a layered
crystalline structure, with the layers less tightly bound to
each other than ions in the structure of detrital minerals.
That is why these minerals are good sorbents for scat-
tered radionuclides and metals. The fine powder fraction
consists of 1) smectites, which can swell considerably,
micas, whose interplanar spacings remain unchanged
under various physicochemical impacts, and 2) minerals
of the kaolin group, with decreased sorption capacity.
Common layered materials of significance in materials
applications include clay minerals and layered double
hydroxide compounds. In general, clay minerals are
Figure 2. Material composition of the sediment samples:
presents a great amount of algae among quartz and mica
debris. Magnification power of ×5000.
comprised of multiple layers of hydroxylated and coor-
dinated tetrahedral and octahedral sheets [26]. Smectite
clays, such as the common mineral montmorillonite, are
characterized by substitution of lower-valency metal
cations (Mg2+ for Al3+ or Al3+ for Si4+) within the sheets
to create a net negative charge that is compensated by
interlayer cations that are typically solvated by water
molecules. The extent of such structural substitutions (as
defined in layer charge) combined with relative humidity
control the swelling ability of smectite minerals. Of most
significance is the ability of many of these layered mate-
rials to intercalate neutral molecules or charged chemical
species (from inorganic metal cations to large organic
polymers and of the metal pollutants and radionuclide
contaminants) into their interlayers [27]. Detailed ex-
amination of the fraction composition of the fine mineral
powder showed the predominance of 0.5-µm to 1.5-µm
particles. The analysis of the obtained data also sug-
gested that mineral particles were subjected to dispersion
and amorphization, resulting in a considerable increase
in the content of X-ray amorphous particles of sizes less
than 0.1 µm. Table 2 lists the oxide composition of the
studied sediment samples.
The high proportion of SiO2 ((56 – 68) mass%) is ob-
viously determined by the geochemical properties of
sediments [4]. The percentage of Al2O3 was also high
(12.4 - 13.1 mass%). Natural mobility of Si and Al is low.
However, SiO2 and Al2O3 are components of sediment
mineral fractions, whose surfaces can have high sorption
capacity due to their considerable porosity and the pres-
ence of charges that create an electrostatic field on the
surface of the mineral. Fe2O3 content varies from 4.6
mass% to 5.3 mass% and MnO from 0.1 mass% to 0.2
mass%, which is characteristic of the sediment of fresh-
water environments. The geochemistry of Fe and Mn is
characterized by their non-uniform distribution in a sedi-

B. Lydia et al. / Natural Science 3 (2011) 517-529 523
ment layer, which is mainly caused by the ability of iron
and manganese to change their valence and be then
transformed to a soluble state. This creates migration
fluxes, which involve other elements associated with Fe
and Mn and their oxides.
Figure 3 shows results of elemental analysis of sedi-
ment sample particles.
The distribution of the elements (Fe, Ca, Mg, Ti, Al,
etc.) in sediment particles is not uniform and differs de-
pending on the origin of the analyzed fragment. This me-
thod is not sensitive enough to determine submicron
quantities of artificial radionuclides.
It is known that as a result of the chemical sorption
(including the mechanisms of chemisorption, ion-exchange
and co-deposition) there occurs the formation of chemi-
cal associates between the surface of a bottom sediment
particle and the ions of radionuclides and (or) their com-
pounds in water. The content of some components of the
bottom sediment absorbing complex with considerable
reactivity can be one of the main indicators of the accu-
mulation capacity of the samples under study with re-
gard to artificial radionuclides. Such components are
clay minerals and clays, specific and non-specific organic
substances, carbonates.
Most widely spread is the method of differential ther-
mogravimetric analysis to determine the main compo-
nents in the absorbing complex of the bottom sediment
according to the sample weight loss when heated at dif-
ferent temperatures. The temperatures used correspond
to the decomposition of one or another bottom sediment
component with the release of volatile products of the
thermal reaction.
The results of the differential thermogavimetry showed
the following. The polar molecular structure of water
contributes to its concentration on the surfaces of Fe-
and Mn-hydroxides, organic substances and both on the
outer surface and in the interlayer space of the clay min-
erals [28]. The water loss upon heating at 105˚C is an
indicator of humidity and is quantitatively connected
with the relatively large surface areas of the compounds
constituting the absorbing complex of the bottom sedi-
ments. As is seen from the given results, the bottom se-
diment sample under study contains about 38 wt% of
adsorption water. This is characteristic of the surface
layer of the bottom sediment (0 - 10 cm) of river systems
with a high rate of water exchange. The amount of СО2
released at the destruction is equal to ~8.6 wt%. It cor-
responds to ~16 mg of the organic substance in 1 g of
the sample. The content of water incorporated in the clay
minerals does not exceed 1 wt%. The weight loss at
8500С caused by the release of СО2 at the decomposition
of the carbonates is equal to about 0.6 wt%.
3.2. Investigation of the Distribution of
Artificial Radionuclides in Sediments
In this study, extraction experiments of the following
artificial radionuclides are discussed: 137Cs, 60Co, 152Eu,
and 241Am. In the study area (from the site drains to the
MCC the boundaries of our study—15 km downstream),
the contents of the radionuclides varied in wide ranges:
137Cs—318-1800 Bq/kg, 60Co—87-720 Bq/kg, 152Eu—
12 - 287 Bq/kg and 241Am—6-76 Bq/kg.
When using scheme 1 it was obtained that the migrat-
ing form (associated with the exchange fraction and
carbonates) was represented by (%): 60Co—4.3-6.9,
137Cs—3.3-3.8, 152Eu—8.2-9.7, 241Am—19.7-29.5. The
content of the radionuclides bound with sesquioxides of
Fe and Mn, as well as with the organic substance of the
bottom sediment under study was determined, these ra-
dionuclides being in a potentially migrating form. The
following radionuclides were extracted (%): 60Co—12.6
- 13.6, 137Cs—2.1 - 5, 152Eu—38 - 51.8, 241Am—13.9 -
43.9. In the undecomposed residue, i.e. in the non-mi-
grating form in the samples studied the content of the
radionuclides corresponds to their physical and chemical
peculiarities and to the type of association with the min-
eral fragments of the bottom sediments. The following
radionuclides were determined (%): 60Co—79.5 - 83.1,
137Cs—9.1 - 94.1, 152Eu—38.5-53.6, 241Am—44.7 - 66.4
(Table 2).
When using scheme 2 in the first fraction radionu-
clides having high migration ability and potentially bio-
available radionuclides were extracted which are poten-
tially dangerous for the environment. The radionuclides
extracted were (%): 60Co—2.3 - 5.5, 137Cs—0.2 - 0.5,
152Eu—0.2 - 0.7. At the destruction of fraction II the
following was extracted (%): 60Co—4.9 - 11.6, 137Cs—
5.8 - 8.1, 152Eu-45.8—55.7, 241Am—33 - 36.7. Fe/Mn
oxides are known to exist as inclusions, concretions,
binding agent between the particles or as covering layers
on the particles. They are perfect radionuclide accumu-
lators. At the destruction of this component under certain
conditions the radionuclide content can considerably
increase both in the pore space and in the mineral resi-
due due to the formation of new compounds different in
solubility and stability (Table 3).
At the destruction of fraction III the following was
extracted (%): 60Co—1.4 - 4.6, 137Cs—7.9 - 8.8, 152Eu—
17 - 27.6, 241Am—31.2 - 49.6. It is believed that under
certain conditions (e.g. with the change of the content of
organic compounds in the aquatic medium [28], the ra-
dionuclides present in the oxidized fraction can again be
involved into the local migration. Consequently, the mo-
iety of the radionuclides present in this fraction indicates
the contribution into the further migratory ability of the
technogenic radionuclides in an aquatic ecosystem.

B. Lydia et al. / Natural Science 3 (2011) 517-529 524
Figure 3. Elemental analysis of the some fragments of a sediment sample by LEO 1430 VP scanning electron microscope
equipped with an OXFORD energy dispersive spectrometer (EDS) (UK). Magnification power of ×3000. Each fragment cor-
responds to the results presented separately: for picture (a) graphics 1 - 2; for picture (b) graphics 1 - 7.

B. Lydia et al. / Natural Science 3 (2011) 517-529 525
Table 2. (a) Sediment oxide composition, mass %; (b) Averaged results of sequential fractionation of sediment samples (scheme 1).
(a)
Oxide compositions Mean Minimum Maximum
SiO2 63 56 68
Ti O2 0.76 0.7 0.8
Al2O3 12.8 12.4 13.1
Fe2O3 4.9 4.6 5.3
MnO 0.14 0.1 0.2
MgO 2.1 1.9 2.3
CaO 2.92 2.9 3.1
Na2O 2.46 2.0 2.9
K2O 1.88 1.7 2.0
(b)
60Co 137Cs 152Eu 241Am
1 2 3 1 2 3 1 2 3 1 2 3
I, % 0.9 2.9 3 2.8 3 0.9 2.1 18.5 2.6
II, % 4.3 6 4.9 0.4 0.8 0.6 5.8 7.3 7.6 11 17.1
III, % 8 8.6 7.2 0.6 0.7 0.8 22.519.8 21 21.8 19.9
IV, % 4.6 5 5 2.3 1.4 4.2 21.818.2 30.8 4 13.9 24
V, % 0.1 0.8 0.5 0.2 10.5 6.1
VI, % 83.1 79.5 82.9 93.7 94.1 90.8 46.453.4 38.5 34.2 60.3 56.1
Table 3. Averaged results of sequential fractionation of sediment samples (scheme 3).
60Co 137Cs 152Eu 241Am
1 2 3 1 2 3 1 2 3 1 2 3
I, % 5.5 2.5 2.3 0.2 0.5 0.7 0.6 0.2
II, % 11.6 5.3 4.9 7.5 8.1 5.8 54.755.7 46.8 36.7 33.0
III, % 4.6 1.4 1.5 8.1 7.9 8.8 23.817 27.6 44 31.2 49.6
IV, % 78.3 90.8 91.3 84.2 83.8 84.9 20.826.7 25.4 19.3 35.8 50.4
The radionuclide content detected at the destruction of
the reducing fraction (scheme 2, fraction II) is higher
than at the destruction of fraction III (scheme 1) similar
in the main components. It is due to the fact that along
with the sesquioxides, iron is also reduced which is
bound with some organic substances, for example, with
fulvic acids, and, therefore, radionuclides are released
forming mixed complexes with these iron compounds
[14]. Probably for this reason the radionuclide redistri-
bution between fractions 2 and 3 is observed according
to scheme 2 as compared to the radionuclide redistribu-
tion between fraction 3 and 4 according to scheme 1.
Moreover, the mobility of the radionuclides associated
with the fraction being reduced is considered to be high-
er than the mobility in the fraction being oxidized.
The radionuclide content present in the non-migratory
form was found in the undecomposed residue after the
sequential extraction according to scheme 2: 60Co—
78.3% - 91.3%, 137Cs—83.8% - 84.9%, 152Eu—20.8% -
26.7%, 241Am—19.3% - 50.4% which was also different
from the radionuclide content in fraction VI according to
scheme 1. This is, probably, due to the fact that at the
previous stages of chemical fractionation the compounds
present in the reduced or oxidized form were destroyed,
e.g. iron compounds [14]. Therefore, a greater number of
radionuclides were extracted associated with these iron
forms.
The high percentages of 152Eu and 241Am in the frac-
tion V+VI (scheme 1) can be accounted for by the pres-
ence of microparticles containing significant radionu-
clide concentrations. The occurrence and the properties
of such particles were described by Bolsunovsky and his
co-authors [29]. A significant part of the radionuclides
released during various nuclear events has been associ-

B. Lydia et al. / Natural Science 3 (2011) 517-529 526
ated with particles. Radioactive or hot particles were
released into the environment as a result of nuclear
weapon tests, fallouts from accidents at nuclear reactors,
discharges from reprocessing plants and associated ra-
dioactive wastes. Therefore, releases of radioactive par-
ticles have occurred more frequently than perhaps usu-
ally anticipated [30]. Most of those particles were ura-
nium containing graphite particles of relatively large size
(300 to 700 μm); practically in all particles 137Cs was the
dominating radionuclide [31,32]. At the same time active
particles with much lower activities (n·101 to n·103 Bq
per particle) were spread more abundantly and could be
demonstrated only in laboratory conditions using re-
peated quartering and high precision gamma-spectros-
copy [32,33]. Their contribution to the total contamina-
tion was significant and reached up to 25% - 100% for
different isotopes in flood land soils [33]. The composi-
tion and size of those particles were not completely clear.
Gritchenko et al. [33] estimated their size to be in the
order of 10 to100 μm. Sukhorukov et al. [32] catego-
rized the active particles into polyisotopic (containing
152Eu, 154Eu, 155Eu, 137Cs, 60Со and 241Am) and monoiso-
topic (60Со or 137Сs) particles.
3.3. Determination of the Relationship
between the Mobility of Artificial
Radionuclides and Mineral and
Geochemical Properties of Sediments
Relationships, including correlations, between the
properties of objects of study and certain parameters of
these objects are investigated using statistical methods or
mathematical models. In this study, correlations between
the species of artificial radionuclides and mineral and
geological parameters of the examined sediments were
obtained using the statistical package of Microsoft Of-
fice Exсel 2003.
60Co interacts, via an ion exchange mechanism, with
compounds present on the surface of clay minerals (r2 =
0.63) and sand (r2 = 0.5). 60Co concentration depends on
the levels of Al2O3 (r2 = 0.75) and K2O (r2 = 0.74), which
are incorporated in crystal structures of sediment parti-
cles. On the other hand, surface phenomena at the inter-
action interface of the two compartments (mineral-
aqueous medium) are known to be caused by the water
molecule adsorption and formation of a hydrate aqua
film on the surface. The hydration degree of the clay
particles is mainly determined by the influence of ca-
tions-compensators (for example, potassium) which are
located on the surface of the solid particles. The cations
– compensators actively attach water molecules to their
surface. This results in weakening the bonds between the
cations and the surface in the aqueous medium, thus, a
number of the cations is removed from the solid particles.
The cations remaining on the surface are considered to
form an adsorption layer and the removed cations create
a diffusion layer. In this connection, the negatively
charged surface of the solid particles and the adsorption
and diffusion cation layers compensating its charge form
a double electric layer of the particle. The double electric
layer structure is not constant but changes with time un-
der the influence of environment conditions [28].
Additionally, mobile species are formed as a result of
60Co interaction with the readily soluble mixed carbon-
ates, which are associated with the surface of the miner-
als containing Al2O3 (r2 = 0.8) and CaO (r2 = 0.94). Par-
ticles of clay minerals and sand are covered with a Fe2O3
polymer film with a high sorption capacity, which inter-
acts with metals that are transported to sediments [34].
Potentially mobile 60Co species may be formed as a re-
sult of 60Co interaction with Fe2O3 (r2 = 0.57), where
they can correlate with MgO (r2 = 0.83). As certain or-
ganic substances (such as lignin) are poorly soluble, the
immobile 60Co may also correlate with the organic con-
tent (r2 = 0.53).
Similarly to 60Co, 152Eu and 241Am interact with fine
carbonate powder, forming mobile species, which mainly
occur on the surface of the sand (r2 = 0.65 and r2 = 0.98
for 152Eu and 241Am, respectively) containing Al2O3 (r2 =
0.87 and r2 = 0.99 for 152Eu and 241Am, respectively).
241Am was found to be related to MgO (r2 = 0.94). As
stated above, the potentially mobile 152Eu and 241Am
react mostly with organic components of sediments (r2 =
0.64 and r2 = 0.66 for 152Eu and 241Am, respectively).
The data on the geochemical composition of sediment
samples showed that a certain portion of the organic
component is firmly bound to the surface of the particles,
mostly clay minerals. Hence, levels of 152Eu and 241Am
in the organic fraction are related to the amount of clay
minerals (r2 = 0.93 and r2 = 0.69 for 152Eu and 241Am,
respectively). The proportion of 241Am associated with
the organic component of the sediment is related to
Al2O3 concentration (r2 = 0.96), whereas 152Eu is related
to Fe2O3 (r2 = 0.78), MnO (r2 = 0.97), and TiO2 (r2 =
0.77). Much of the potentially mobile portion of 152Eu
and 241Am is formed by the interaction of the radionu-
clides with Fe and Mn oxides, which belong to the frac-
tion “sesquioxides and hydroxides” (III): r2 = 0.85 for
241Am-Fe2O3 and r2 = 0.92 for 152Eu-MnO. In the same
fraction, 241Am concentration is related to the levels of
CaO (r2 = 0.89), Na2O (r2 = 0.81), and K2O (r2 = 0.93).
As assumed previously [3,17], the immobile 152Eu and
241Am were mainly bound to clay minerals (r2 = 0.91 and
r2 = 0. 79 for 152Eu and 241Am, respectively). Analysis of
the relationships for the chemical fractions of 152Eu and
241Am showed that the radionuclide amounts extracted

B. Lydia et al. / Natural Science 3 (2011) 517-529 527
from the organic fraction correlated with their concen-
trations in the residual solids (r2 = 0.82 and r2 = 0.97 for
152Eu and 241Am, respectively). This can indicate that
under different conditions, radionuclides can be con-
verted from the potentially mobile form to the immobile
one. The conditions can be changed if, for instance, sedi-
ment humic substances are humified, forming poorly so-
luble humus. On the other hand, the immobile form can
become more readily soluble and, thus, more mobile.
A mobile species of 137Cs is formed when the ra-
dionuclide interacts, via an ion exchange mechanism,
with Na2O (r2 = 0.98) and K2O (r2 = 0.78), which are
present in the diffuse layer on the surface of sediment
particles, including the sand (r2 = 0.62). The amount of
potentially mobile 137Cs is mainly related to concentra-
tions of Fe2O3 (r2 = 0.78) and MnO (r2 = 0.57) in the
fraction “sesquioxides and hydroxides” and to MnO
concentration (r2 = 0.63) in the organic fraction of the
sediment. 137Cs, which can be incorporated into crystal-
line structures of primary and secondary minerals, be-
comes firmly bound to particles of sand (r2 = 0.62) and
clay minerals (r2 = 0.93), in which it resides in the im-
mobile form. Correlation analysis of 137Cs concentra-
tions in the chemical fractions indicated a relationship
between the mobile 137Cs concentration (“carbonates”)
and the potentially mobile 137Cs concentration (“organ-
ics”) (r2 = 0.91). So, a change in geochemical conditions,
resulting in various transformations in sediments, can
cause a reversible redistribution of 137Cs between less
mobile and more mobile forms.
Thus, we can make the following assumptions. The
mobility of artificial radionuclides is directly related to
the mineral and geochemical properties of the sediments
they interact with: the structure and the composition of
the minerals determine the type of sedimentary struc-
tures that form on their surface. The surface can be
composed of fine-crystalline or amorphous deposits, or a
mixture of both. In addition to this, the surface can be
positively or negatively charged. These factors affect
possible mechanisms of the uptake of metals and ra-
dionuclides from the liquid layer that contacts the sedi-
ments. The presence and the degree of the physico-
chemical affinity between the radionuclides and the ele-
ments comprising the sediment mineral component de-
termine the stability or instability of the relationships
between them. For instance, the interaction between ra-
dionuclides and the exchangeable fraction of sediments,
via an ion exchange, results in the formation of unstable
associates. As the exchangeable fraction is usually char-
acterized as a diffuse layer on the surface of the particles,
the associates are easily destroyed to form soluble com-
pounds. 137Cs, e.g., correlates well with Na and K com-
pounds in the exchangeable fraction because these ele-
ments are alkali metals and have similar physicochemi-
cal properties (Table 2).
Sediments contain various poorly soluble carbonate
compounds (up to 3.3 mass%). If, however, the condi-
tional equilibrium in a sediment layer is somewhat
shifted (e.g., if the sediment is acidulated due to humifi-
cation processes), this can result in the formation of hy-
drogen carbonates or their complete transformation. Thus,
radionuclides bound to the chemical fraction “carbon-
ates” are converted into other species, which have dif-
ferent solubility properties and, hence, different mobility.
This can be confirmed by the positive correlations ob-
tained for 60Co- CaO , 241Am-MgO and 137Cs associated
with the fractions “carbonates” and “organics” (Table 2).
Fe and Mn sesquioxides and hydroxides, forming po-
lymer film on the surface of mineral particles, bind con-
siderable amounts of radionuclides, which change their
valence and, hence, are able to form redox pairs with the
corresponding potential, such as 60Co- Fe2O3, 152Eu-
-Fe2O3-MnO. Moreover, the film formed by sesquiox-
ides and hydroxides has charged sites, which bind ra-
dionuclide compounds with a corresponding opposite
charge, e.g., 137Cs-Fe2O3-MnO, 241Am-Fe2O3. Iron, how-
ever, can be a component of both silicate and non-sili-
cate compounds [17]. Thus, radionuclides with similar
physicochemical properties can form such compounds
with Fe, e.g., 60Co (fractions V+VI)-Fe2O3.
The organic constituent of sediments consists mainly
of humic substances: humic acids, fulvic acids, and
humin [4]. The proportions of these components deter-
mine the percentage of radionuclides bound to the or-
ganic fraction [14,17]. As organic substances rather
firmly adhere to a large part of the surface of sediment
particles, their reactivity also depends on the reactivity
of humic substance components. The percentages of
152Eu and 241Am associated with organics, particularly
with low-molecular-weight and free fulvic acids, were
the highest among the radionuclides examined in this
study [17]. The total amount of organics correlates with
clay minerals: their layered structure makes them pene-
trable by organic substances and their complexes with,
e.g., radionuclides. On the other hand, certain compo-
nents of the organics contained in sediments are resistant
to chemical reagents (such as lignin). This portion of
organics, together with associated radionuclides, stays in
the residual solids, i.e. is considered to be firmly bound
to the mineral structures of sediments; for instance, 152Eu
and 241Am concentrations associated with the organics
correlate with the residual solids.
Geochemically speaking, residual solids are a coarse
fraction of sediments, consisting of insoluble crystalline
structures. Residual solids also contain clay minerals
deformed by chemical fractionation and an insignificant

B. Lydia et al. / Natural Science 3 (2011) 517-529 528
portion of insoluble organics. Hence, radionuclides as-
sociated with residual solids are bound to them either via
the mechanism of isomorphic incorporation in the crys-
tal lattices of silicate structures (e.g., 137Cs concentration
correlates with the portions of sand and clay minerals) or
as a result of compound formation in interlayer spaces of
clay minerals (e.g., interaction of 152Eu and 241Am with
clay minerals).
4. CONCLUSIONS
The results of this study suggest the following conclu-
sions:
1) The fractionation according to scheme 2 is mainly
based on the physical-chemical properties of the ele-
ments included into the mineral geochemical compo-
nents of the bottom sediments, e.g. iron compounds. In
this connection there is some overlapping between the
main fractions and, thus, the redistribution between the
forms of existence, whereas fractionation according to
scheme 1 is based on the properties of the mineral com-
positions of the bottom sediments. However, when using
both fractionation schemes it is possible to compare the
obtained results and use them for a more complete de-
scription of the radionuclide behavior in the bottom se-
diments.
2) The identified correlations can indicate that under
different conditions, radionuclides can be converted
from the potentially mobile form to the immobile one.
As changing conditions can be considered, for instance,
sediment humic substances are humified, forming poorly
soluble humus. But on the other hand, the immobile
form can become more readily soluble and, thus, more
mobile. In the latter case, it formed flows of secondary
contamination of the Yenisei River floodplain radionu-
clides.
5. ACKNOWLEDGEMENTS
The authors would like to express their gratitude to Razvorotneva
L.I., Ph.D., and Armancheva T.A. and Dubova V.P., technicians, at the
Institute of Geology and Mineralogy SB RAS, and to Kolmogorov Y.P.,
a technician of the Elemental Analysis Station at the VEPP-3 of the
Institute of Nuclear Physics SB RAS.
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