Journal of Geoscience and Environment Protection, 2014, 2, 153-158
Published Online June 2014 in SciRes. http://www.scirp.org/journal/gep
How to cite this paper: Bolsunovsky, A., & Melgunov, M. (2014). A Study of Sediments and Radioactive Particles of the
Yenisei River Using a Variety of Analytical Methods. Journal of Geoscience and Environment Protection, 2, 153-158.
A Study of Sediments and Radioactive
Particles of the Yenisei River Using a
Variety of Analytical Methods
A. Bolsunovsky1, M. Melgunov2
1Institute of Biophysics SB Russian Academy of Sciences, Krasnoyarsk, Russia
2Institute of Geology and Mineralogy SB Russian Academy of Sciences, Novosibirsk, Russia
Received April 2014
The Yenisei River, one of the largest rivers in the world, is contaminated with artificial radionu-
clides released by a Russian nuclear facility producing weapon-grade plutonium, which has been
in operation for many years. Examination of Yenisei River sediment samples revealed the pres-
ence of artificial radionuclides typical of radioactive discharge from the Mining-and-Chemi cal-
Combine (MCC) nuclear facility: isotopes of europium (152Eu, 154Eu, and 155Eu), cesium (137Cs and
134Cs), 60Co, 90Sr, and transuranium elements. The MCC is also a source of radioactive particles in
the Yenisei. New data on radionuclide concentrations in sediments and radioactive particles in the
Yenisei River were obtained using a wide range of analytical methods. Sequential extraction per-
formed on samples of sediment cores showed different degrees of potential environmental avail-
ability of artificial radionuclides and uranium. In a few samples, 241Am was present in the unex-
tractable form, which may be accounted for by the presence of microparticles of the reactor fuel.
These microparticles were investigated using scanning electron microscopy, and their reactor
origin was confirmed.
Yenisei River Sediments, Artificial and Natural Radionuclides, Radioactive Particles,
Sequential Extraction, Radionuclide Composition and Speciation, Analytical Methods
The Yenisei is one of the world’s largest rivers, over 3000 km long, flowing into the Kara Sea. The Min-
ing-and-Chemical Combine (MCC) of Rosatom is located at Zheleznogorsk in the Krasnoyarsk Territory, on the
bank of the Yenisei River, 60 km downstream of the city of Krasnoyarsk. The Combine has been producing
weapons-grade plutonium in uranium-graphite reactors since 1958, when the first reactor was started up. The ir-
radiated uranium is reprocessed at the radiochemical plant to separate uranium, plutonium, and fission products.
The reactor plant houses three reactors. Two of them used the Yenisei water as coolant, i.e. the water was taken
from the river to remove heat from the core, passed through the reactor fuel channels, and returned to the Yeni-
A. Bolsunovsky, M. Melgunov
sei. Both of these reactors were shut down in 1992, the third reactor was shut down in 2010. The radiochemical
plant and other MCC facilities are still operating. Several scientific expeditions revealed that the Yenisei River
floodplain is contaminated with artificial radionuclides, including plutonium isotopes, within 2000 km down-
stream of the MCC (Bolsunovsky et al., 2002; Klemt et al., 2002; Bolsunovsky & Bondareva, 2007; Bol-
sunovsky et al., 2007; Bolsunovsky, 2010, 2011; Bolsunovsky & Dementyev, 2010; Semizhon et al., 2010).
Since 1995, researchers of the Institute of Biophysics (Krasnoyarsk) and the Institute of Geology and Mineral-
ogy (Novosibirsk) have found radioactive particles in floodplain soils and sediments during their sampling
campaigns at the Yenisei (Bolsunovsky & Tcherkezian, 2001; Bolsunovsky, 2009; Chuguevskii et al., 2010).
The source of these particles is the MCC, and they contain not only fission radionuclides (isotopes of cesium,
plutonium, americium, curium, strontium) but also activation radionuclides (europium isotopes, 60Co). The
MCC is also a source of uranium isotopes in the Yenisei. Thus, the Yenisei River basin is a unique environment
for studying the mobility of both artificial radionuclides and uranium isotopes in the aquatic ecosystem. To ef-
fectively carry out such studies, researchers should employ a variety of methods, including nondestructive ones.
The purpose of this study was to obtain new data on concentrations of radionuclides in sediments and radio-
active particles of the Yenisei River by using a wide range of analytical methods.
2. Materials and Methods
About 200 sediment cores were collected from the channel bed of the Yenisei River at different distances down-
stream of the MCC during 1997-2012 (Figure 1). For comparison purposes, we also collected sediment cores at
a position upstream of the MCC, at the village of Esaulovo (45 km downstream of Krasnoyarsk) and at the city
of Krasnoyarsk (Figure 1). The diameter of the sampler (made in Russia) was 11 cm and it was able to collect
cores up to 180 cm long. Each sediment sample was a 3-cm thick layer, except for the top sediment layer, whose
thickness ranged from 4 to 10 cm, depending on the core moisture content. In the laboratory, some sediment
samples were dried, but several samples were maintained wet and subjected to sequential extraction. The maxi-
mum number of layers for a core was 46, and the maximum length of the core was 147 cm. We also studied ra-
dioactive particles extracted from sediments and floodplain soils of the Yenisei River.
Radionuclide measurements were performed using a wide range of instrumental methods: gamma-spectro-
metry with a “Canberra” spectrometer (U.S.), mass spectrometry with an “Agilent” spectrometer (U.S.), al-
pha-spectrometry with a EURISYS MEASURES spectrometer (France), and neutron activation analysis. Activ-
ity concentrations of radionuclides in sediment layers were decay corrected to the sample collection dates. Ra-
dioactive particles were additionally investigated using scanning electron microscopy (SEM) at the Institute of
Geology and Mineralogy in Novosibirsk (Russia), with a LEO1430VP scanning electron microscope equipped
with an “OXFORD” energy-dispersive spectrometer.
Binding of radionuclides to sediment samples was examined using sequential extraction technique proposed
by Tessier and modified by Klemt and coauthors (Klemt et al., 2002; Semizhon et al., 2010). Six fractions were
produced: I—Exchangeable Ions; II—Carbonates; III—Oxides and Hydroxides of Iron and Manganese; IV—
Organic Matter; V—Amorphous silicates; VI—Residuals. It has generally been accepted that the less radionu-
clide activity is retained in the residual solids (Fraction VI), the more mobile this radionuclide is in the sediment.
Investigations and development of the X-ray fluorescence technique for determining the elemental composi-
tion of sediment were carried out on a VRA-20R Carl Zeiss fluorescent X-ray analyzer (Jena, Germany) at the
Institute of Geology and Mineralogy in Novosibirsk (Russia). Results are reported in Table 1 (Bolsunovsky,
2010). As expected, river bottom sediments contained a large amount of SiO2 (56 - 68 mass%). There was also a
considerable percentage of Al2O3 (12.4 - 13.1 mass%). The percentage of Fe2O3 varied from 4.6 to 5.3 mass%
and that of MnO constituted 0.1 - 0.2 mass%, as is typical of freshwater sediments. Percentages of Fe and Mn in
sediment samples and their vertical distribution in sediments are commonly accepted indicators of the direction
and features of geochemical processes. The samples also contained MgO, CaO, Na2O, K2O, and TiO2, which did
not exceed 2 - 3 mass%.
3.1. An Analytical Study of Concentrations of Radionuclides and Strength of Their
Binding in Sediments of the Yenisei River
Gamma-spectrometry measurements of sediment samples showed artificial radionuclides typical of the radioac-
A. Bolsunovsky, M. Melgunov
Figure 1. Map of the south of the Krasno-
yarskii Krai (Russia), showing the MCC fa-
cility and settlements near where sediment
samples were collected. Scale 1:2800000.
Table 1. Results of X-ray phase analysis of sediments, mass% (Bolsunovsky, 2010).
SiO2 63 56 68
TiO2 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 2.9 2.8 3.1
Na2O 2.5 2.0 2.9
K2O 1.9 1.7 2.0
tive discharge from the MCC to the Yenisei River: isotopes of europium (152Eu, 154Eu, and 155Eu), cesium (137Cs
and 134Cs), 60Co, and the transuranium element 241Am. The vertical distribution of radionuclides in the sediment
cores is complex and there are several concentration minimums and maximums due to different amounts of ra-
dionuclides released by the MCC and due to variations in global fallout. Artificial radionuclides were detected in
sediment layers both at the MCC and at considerable distances downstream of the nuclear facility. For the sedi-
ment core collected at site Kargino (320 km downstream of Krasnoyarsk), the maximum 137Cs activity concen-
trations (up to 900 Bq∙kg−1) were recorded in the middle and the lower parts, with relatively low concentrations
at the surface. 241Am (up to 10 Bq∙kg−1) was also detected in the Kargino core (Figure 2). For the sediment cores
collected near the MCC, maximum 137Cs and 241Am activities were several times higher: up to 4000 and 240
Bq/kg, respectively (Bolsunovsky et al., 2002, 2007; Bolsunovsky & Bondareva, 2007; Bolsunovsky, 2010).
The fact that some sediment layers contained high 241Am concentrations could be indicative of high concentra-
tions of other transuranium elements. Further analysis of the sediment layers that contained maximum levels of
A. Bolsunovsky, M. Melgunov
Figure 2. Representative vertical distribution profiles of radio-
nuclides in channel bed sediments (Bq/kg dry mass) of the Ye-
nisei River near the villages of Esaulovo (45 km downstream of
Krasnoyarsk) and Kargino (320 km downstream of Krasnoyar-
sk). See Figure 1 for locations.
radionuclides, including 241Am, indicated that the Yenisei River sediment samples had local anomalous hotspots
with high activity concentrations of transuranium elements, which were 100 times higher than their global fall-
out levels (Bolsunovsky et al., 2002, 2007; Bolsunovsky & Bondareva, 2007; Bolsunovsky, 2010).
In layers of sediment cores collected at a position upstream of the MCC (the village of Esaulovo), the level of
137Cs (up to 10 Bq/kg dry mass) can be accepted as the background value of radioactive contamination of sedi-
ments in this section of the Yenisei, due to global fallouts of 137Cs (Figure 2). In addition to artificial radionu-
clides, MCC effluents contain uranium isotopes. Our results suggest that upstream of the MCC, at the city of
Krasnoyarsk and the village of Esaulovo, the average 238U concentration in sediments is about 3.0 mg/kg dry
mass. In sediments collected at the place where the MCC releases its radioactive water (at the villages of Ata-
manovo and B. Balchug), 238U concentration is 1.5 times higher, reaching 4 - 5 mg/kg. In some tributaries of the
Yenisei River, close to Rosatom facilities, the highest 238U concentrations in sediment layers amount to 6 mg/kg.
Sequential extraction techniques are the most common method of studying radionuclide speciation in soils
and sediments. Sequential extraction performed on samples of the upper layers of the sediment core collected
near the MCC showed (Figure 3) that the amounts of extracted 90Sr, 152Eu, and 241Am were the largest (reaching
80% of initial activity), then followed 60Co (30%), 238,239,240Pu (15% - 30%), and, last, 137 Cs (5% - 15%). The
distribution of 238U among chemical fractions of sediments was similar to that of 60Co. The largest amounts of
the radionuclides were extracted from such fractions as organic matter (Fraction IV) and oxides and hydroxides
of iron and manganese (Fraction III). In a few samples, almost all 241Am was present in the unextractable form
(Fraction VI), which may be accounted for by the presence of microparticles of the reactor fuel. Assessment of
potential environmental availability of artificial radionuclides in the analyzed sediments from the Yenisei River
was based on the data for the first four fractions (Exchangeable Ions, Carbonates, Oxides and Hydroxides of
Iron and Manganese, and Organic Matter) of sequential extraction. Based on our results (Figure 3), we arranged
radionuclides in the following sequence, showing their relative mobility in the upper layers of the cores (Bolsu-
A. Bolsunovsky, M. Melgunov
Figure 3. Typical distribution of radionuclide activities among
chemical fractions of the upper layers of the sediment collected
near the MCC (Bolsunovsky, 2011). Fractions: I—Exchange-
able Ions; II—Carbonates; III—Oxides and Hydroxides of Iron
and Manganese; IV—Organic Matter; V—Amorphous silicates;
novsky, 2010, 2011):
3.2. An Analytical Study of Radioactive Particles of the Yenisei River
As noted above, since 1995, researchers of the Institute of Biophysics (Krasnoyarsk) and the Institute of Geol-
ogy and Mineralogy (Novosibirsk) have found a number of radioactive particles in floodplain soils and sedi-
ments during their sampling campaigns at the Yenisei (Bolsunovsky, Tcherkezian, 2001; Bolsunovsky, 2009;
Chuguevskii et al., 2010). Analytical studies showed that these particles contained not only fission radionuclides
(isotopes of cesium, plutonium, americium, curium, strontium) but also activation radionuclides (europium iso-
topes, 60Co). The highest 137Cs activity in the particles reached 30 MBq/particle (Bolsunovsky & Tcherkezian,
2001; Bolsunovsky, 2009). Investigations of radioactive particles performed in Russian and Norwegian labora-
tories proved their reactor origin. Based on comparative analysis of 137Cs/134Cs ratios, all the particles can be di-
vided into three major groups, suggesting that over the 50-year period of the MCC operation, there had been
three emergency situations at the MCC reactors, with nuclear fuel microparticles released into the Yenisei. In-
vestigations carried out in Novosibirsk and Krasnoyarsk institutes showed that alluvial soils and sediments of
the Yenisei floodplain downstream the MCC are contaminated by radioactive particles of various types and ac-
tivities (Bolsunovsky, 2009; Chuguevskii et al., 2010). All the particles can be divided into two classes of activ-
ity: 1) radioactive particles with the activity of 137Cs (or another radionuclide) from several kBq/particle to sev-
eral tens of MBq/particle, and the number of such particles in the Yenisei floodplain is roughly estimated as 100
particles/km2; 2) radioactive microparticles with the activity of 137Cs (or another radionuclide) from several
Bq/particle to several hundred Bq/particle. These microparticles were investigated and their reactor origin was
confirmed. As an example, Table 2 gives results of scanning electron microscopy of one particle. The spatial
distribution of some elements over the scanned surface of the isolated particle region obtained by energy-dis-
persive analysis shows that at points 1 - 3, the major element of the particle is uranium, while at points 4 and 5,
carbon is the main element of the particle matrix. These data are indicative of the uranium-graphite (i.e. nuclear
fuel) origin of this particle (Chuguevskii et al., 2010).
By using modern spectrometric methods, we determined a great number of artificial and natural radionuclides in
sediments and radioactive particles of the Yenisei River. Scanning electron microscopy of microparticles proved
their reactor origin. Binding of radionuclides to sediment samples was examined using sequential extraction
technique. Based on results obtained, we arranged artificial radionuclides and uranium in the sequence showing
their relative mobility in the layers of the sediment core.
Sr-90 Am-241 Eu-152Co-60U-238Pu-
239,240 C s-137
A. Bolsunovsky, M. Melgunov
Table 2. Elemental composition (%) of hot particles (Chuguevskii et al., 2010).
Points of analysis of the particle
1 2 3 4 5
C 5.2 7.4 7.7 65.3 88.2
O 19.6 17.5 22.4 25.3 11.4
Si 1.1 0.6 0.4
U 75.2 75.1 68.8 3.7
Total, % 100 100 100 100 100
The study was partly supported by Russian Foundation for Basic Research (RFBR) Grant No 12-05-00078
and IAEA Research Contract No 17941.
Bolsunovsky, A. (2009). Hot Particles in the Floodplain of the Yenisei River. In Radioactive Particles in the Environment.
Springer, 111-121. http://dx.doi.org/10.1007/978-90-481-2949-2_6
Bolsunovsky, A. (2010). Artificial Radionuclides in Sediment of the Yenisei River. Chemistry and Ecology, 26, 401-409.
Bolsunovsky, A. (2011). Radionuclide Speciation in Sediments of the Yenisei River. Radioprotection, 46, S195-S198.
Bolsunovsky, A., & Bondareva, L. (2007). Actinides and Other Radionuclides in Sediments and Submerged Plants of the
Yenisei River. Journal of Alloys and Compounds, 444-445, 495-499. http://dx.doi.org/10.1016/j.jallcom.2007.01.146
Bolsunovsky, A., & Dementyev, D. (2010). Sediments of the Yenisei River: Monitoring of Radionuclide Levels and Estima-
tion of Sedimentation Rates. IAHS Publ., No337, 143-148.
Bolsunovsky, A. Ya., & Tcherkezian, V. O. (2001). Hot Particles of the Yenisei River Flood Plain, Russia. Journal of Envi-
ronmental Radioactivity, 57, 167-174. http://dx.doi.org/10.1016/S0265-931X(01)00021-2
Bolsunovsky, A., Ermakov, A., & Sobolev, A. (2007). New Data on Transuranium Elements in the Ecosystem of the Yenisei
River Floodplain. Radiochimica Acta, 95, 547-552. http://dx.doi.org/10.1524/ract.2007.95.9.547
Bolsunovsky, A. Ya., Ermakov, A. I., Myasoedov, B. F., Novikov, A. P., & Sobolev, A. I. (2002). New Data on the Content
of Transuranic Elements in Bottom Sediments of the Yenisei River. Transactions Dokl Akad Nauk, 387, 233-236.
Chuguevskii, A. V., Sukhorukov, F. V., Melgunov, M. S., Makarova, I. V., & Titov, A. T. (2010). “Hot” Particles of the
Yenisei River: Radioisotope Composition, Structure, and Behavior in Natural Conditions. Doklady Earth Sciences, 430,
Klemt, E., Spasova, Y., Zibold, G., & Bolsunovsky, A. (2002). Deposition of Artificial Radionuclides in Sediments of the
River Yenisei. In P. Strand, T. Jolle, & A. Sand (Eds.), Environmental Radioactivity in the Arctic & Antarctic (pp. 67-70).
Norway: Norwegian Radiation Protection Authority.
Semizhon, T., Röllin, S., Spasova, Y., & Klemt, E. (2010). Transport and Distribution of Artificial Gamma-Emitting Radio-
nuclides in the River Yenisei and Its Sediment. Journal of Environmental Radioactivity, 101, 385-402.