Radioactivity Assessment of Sapropel Sediments in Small Lakes in the Baraba Lowland and Kulunda Plain, West Siberia

ISSN 0016-7029, Geochemistry International, 2022, Vol. 60, No. 8, pp. 792–807. © Pleiades Publishing, Ltd., 2022.
Russian Text © The Author(s), 2022, published in Geokhimiya, 2022, Vol. 67, No. 8, pp. 787–804.
Radioactivity Assessment of Sapropel Sediments in Small Lakes
in the Baraba Lowland and Kulunda Plain, West Siberia
V. D. Strakhovenkoa, *, E. A. Ovdinaa, I. N. Malikovaa, and G. I. Malova
a Sobolev Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
*e-mail: strahova@igm.nsc.ru
Received January 17, 2021; revised January 17, 2021; accepted March 20, 2021
Abstract—Various components of lake systems located in different landscape zones in southern West Siberia
were studied for contents of natural and artificial radionuclides, following the requirements of the state standards (GOST). This work aims at assessing the radiation state of lacustrine sapropel sediments in the Baraba
lowland and Kulunda plain, taking into account their natural features and the degree of contamination during
nuclear tests. It was found out that the values of the total effective specific activity (As) of natural radionuclides in all of the sapropel lacustrine sediments are significantly lower than the standard value (according to
the requirements of the GOST). Some sapropel horizons in the lakes contain excess 137Cs reserves that are
twice as high as the global background. Such lakes tend to be spatially constrained to areal traces of radioactive
fallouts after nuclear tests at the Semipalatinsk test site and undoubtedly belong to lake systems whose waters
and soils on catchments were primarily contaminated with radiocesium.
Keywords: sapropel, total effective specific activity, natural radionuclides, radiocesium, small lakes, southern
West Siberia
DOI: 10.1134/S0016702922080080
INTRODUCTION
Newly acquired data on the global transfer of sedimentary material have remarkably modified traditional understanding of globally operating laws that
control biochemical and mechanical processes of continental sedimentation, and this calls for further studies of lacustrine sediments with the application of
modern analytical techniques (Stein, 2008; Wan et al.,
2008; Lisitsyn, 2014; and others).
Sapropels are formed in anaerobic environments as
a result of physicochemical and biological transformations of hydrobionts, at the variable involvement of
mineral and organic components, which actively
interact with one another (Kemp et al., 1999; Kurzo
et al., 2010; Strakhovenko et al., 2016; and others).
The composition of sapropels can notably vary
depending on their genesis, with the organic components differing primarily in the proportions of the biological contributions of various organisms (Strakhovenko et al., 2014; Serebrennikova et al., 2017;
Taran et al., 2018; and others). Terrigenous particles in
sapropel are mostly fragments of rocks brought from
the catchments. The lakes discussed herein lie mostly
in the southeastern West Siberian Platform, which
geologically consists of two floors: a folded basement
and sedimentary cover. The basement is made up of
folded shales, limestones, and sandstones that locally
host magmatic rocks. The basement crops out near the
city of Novosibirsk and is overlain with the sedimentary cover east of it, with the thickness of the cover
reaching 3 km at the western boundary of this territory.
The complete vertical section of the sedimentary cover
consists of alternating marine and continental Jurassic, Cretaceous, and Paleogene rocks. The surface of
the whole territory was uplifted in the latest Paleogene
and became free of seawater. A river network was
formed there, the rock in adjacent areas in the Altai
were eroded, and the eroded material was transported.
The Neogene and Quaternary rocks are continental.
The surface rocks at the territory are loams and clays,
which were immediately involved in the development
of the local surface topography, the origin of the soils,
and the vegetation. In the Neogene–Quaternary, the
local plains (Vasyugan, Ob, Kulunda, and Baraba)
subsided at variable rates, and this resulted in that the
Baraba lowland became enclosed and undrained, and
its absolute elevations reached 100–120 m, i.e., 20 m
lower than the elevations of the former three plains.
No glaciers covered this territory in the Quaternary,
however, the melting of glaciers in nearby Altai areas
enhanced the streams. The removal of rock fragments
and the products of their weathering thus also
increased, as also was enhanced their accumulation on
the plains (Explanatory Notes…, 1967). Terrigenous
alluvial–proluvial sediments in the West Siberian
Lowland were produced by material eroded from
Paleozoic formations in the Altai–Sayan and Kazakh-
792
RADIOACTIVITY ASSESSMENT OF SAPROPEL SEDIMENTS IN SMALL LAKES
stan, and the radiogeochemical levels of these rocks
were close to the average level of the continental crust.
The chemical composition of sapropels is controlled
not only by the contribution of clastic material but also
(and mostly) by the biogeochemical processes in the
water and the few uppermost centimeters of the bottom sediments (Newsome et al., 2014; Strakhovenko
et al., 2018; and others). Still another important
source of material brought to small lakes from nearby
watersheds in West Siberia, where soils are formed on
loess loams, is the wind erosion of soils, a process
that is particularly intense during dust storms, which
became more frequent after the tilling of the wild
lands (Nalivkin, 1969; Gavshin et al., 1999; Shevchenko et al., 2012; and others).
The biological constituent of sapropels of the lakes
in question was documented in detail by N.I. Ermolaeva and E.Yu. Zarubina (Institute of Water and
Environmental Problems, Siberian Branch, Russian
Academy of Sciences). It has been demonstrated in
numerous publications that production processes in
most of the lakes were more intense than the destruction processes, and the rate of addition of organic
compounds to the bottom sediments as a result of
decomposition of macrophyte and zooplankton die-off
was evaluated. The production of phytoplankton in the
lakes broadly varied from 0.01 to 1.96 mg O2/(L × h).
The lakes characterized by the microphytogenic type
of their sapropel-forming processes and by a high
annual production of the phytocenoses (up to 2261 g
organic matter/(m2 × year)) are also characterized by
the highest concentrations of organic carbon (TOC,
total organic carbon). The contributions of various
hydrobiont groups to the bottom sediments can significantly differ and variably affect the composition of
the sediments (Zarubina, 2013; Ermolaeva et al., 2017;
Zarubina et al., 2018; Zarubina and Fetter, 2019;
Ermolaeva et al., 2019; and others).
Systematic studies of sapropels were launched in
1916 on the initiative of Academicians N.S. Kurnakov
and V.I. Vernadsky. The Sapropel Institute, which was
established in 1932, conducted extensive academic
research and resolved much applied problems. The
later development of large oil and gas fields and hydrocarbon chemical processing then hampered studies
aimed at the utilization of sapropels and accordingly
led to the shrinkage of sapropel studies. Russia possesses uniquely large resources of sapropels, which
vary from 38 to 250 billion of cubic meters according
to various evaluations (Shtin, 2005), but no more than
2% of them is explored and adequately studied. Modern technological approaches enable the highly efficiently utilization of both sapropels themselves and
solid and liquid products of their processing in various
fields of economy and various industries, and this
revived interest in the utilization of sapropels, including those from deposits in West Siberia. It is also
important that the removal of sapropel from water
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bodies improves the quality of the water and conditions for fish farming in these bodies.
Sapropels usable in various sectors of national
economy must comply with a range of state standards
(GOSTs). According to GOST 54000-2010, raw sapropel must meet radiation hygienical standards on the
activities of natural and artificial radionuclides.
Nuclear tests at the Semipalatinsk and Novaya
Zemplya testing sites (starting in 1949) and the nuclear
disasters at the Chernobyl Atomic Power Plant in 1986
and at the Fukushima 1 Atomic Power Plant in 2011
resulted in that small areas where regional anthropogenic radiation background was several times higher
than the global radiation background emerged practically throughout the whole study area in West Siberia
(Izrael’, 2000; Sukhorukov et al., 2001; Izrael’, 2005;
Rikhvanov, 2009; and others). Russia and other countries conventionally use 137Cs as an indicator (marker)
of nuclear contamination and the level of radiation
impact. The 137Cs isotope is a long-lived artificial
radionuclide, whose half-life is 30.2 years and which is
produced at nuclear blasts and in the course of operation of nuclear power plants. It is relatively stable (little
migrating) in soils and is relatively easy to identify by
currently utilized analytical techniques. The standardized pollution indicators used in Russia is the specific
activity (Bq/kg) and fallout density (reserve) of 137Cs
in soil in mCi/km2, which characterizes the current
state of a given territory and provides a basis for evaluating the accumulated effective radiation dose (cSv)
(Myasnikov, 2004). The global activity background of
137Cs in soils in West Siberia is, according to expert estimates based on several archive, calculation, and experimental 137Cs measurements in soils), 50 mCi/km2
(1.85 kBq/m2) as of 1995 (Baranov, 1956; Boltnev
et al., 1972; Aleksakhin, 1982; Chernyago et al., 2004;
Medvedev et al., 2005; and others). Note that global
fallouts in Siberia were only insignificantly contributed (no more than 10%) by radiocesium from the
Chernobyl APP, as follows from the activity ratio of
137Cs/134Cs (Gavshin et al., 2000; Sukhorukov et al.,
2001). Earlier publications report data on radiocesium
reserves in off-system units of radiocesium activity
(Ci), including those widely quoted herein, because of
which below we report radiocesium reserves in
mCi/km2, and which can be recalculated into kBq/m2
as 1 Ci/km2 = 37 kBq/m2 (Pavlotskaya, 1974; Moiseev, 1975; Izrael’, 2000; Mikhailovskaya et al., 2015;
and others). Acad. Yu.A. Izrael’ has published, in his
paper issued in 2000 and materials of 2005, a map of
137Cs reserves (mCi/km2 ) recalculated to the year
2000, and has demonstrated that the global radiation
monitoring carried in the 1990s using aerial gammaspectral survey and practically ubiquitous sampling
had revealed a latitudinal zoning in the distribution of
137Cs pollution. As a result of a great number of nuclear
tests in the northern hemisphere and, particularly,
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STRAKHOVENKO et al.
atmospheric circulation because of the much lower
meridional movement velocity compared to the latitudinal ones, the maximum global radiation background
reportedly occurs within two latitudinal belts at 40°–
50° and 50°–60° N (the radiation background caused
by 137Cs in the latitudinal belt of 50°–60° varies within
the range of mCi/km2 i.e., 0.4–2.0 kBq/m2 in recalculation to the year 2012; Usacheva, 2017), and this value
decreases both north- and southward (Izrael’ et al.,
2000; Izrael’, 2005).
Radiocesium concentrations caused by local and
regional fallouts were determined to show a mosaic
distribution pattern, which is explained by both the
heterogeneity of the primary radioactive fallouts and
the uneven secondary redistribution (Sukhorukov
et al., 2001; Malikova et al., 2011; and others).
Our research was aimed at estimating the radioactive radiation state of lacustrine sapropel sediments in
the Baraba lowland and Kulunda plain in West Siberia, with regard to their inherent natural features and
their contamination during nuclear tests.
MATERIALS
This study was carried with sapropel bottom sediment in small lakes in the Baraba lowland and Kulunda
plain. The total number of lakes in the Baraba lowland
and Kulunda plain exceeds 5000, and the aggregate surface area of the lakes exceeds 8000 km2. Most of the
lakes are undrained (basinal) and small: 97.5% are
smaller than or equal to 2.5 km2. Our study is based on
factual materials collected by the authors, in cooperation with researchers from the Institute of Water and
Environmental Problems, Siberian Branch, Russian
Academy of Sciences, in the course of fieldwork conducted starting from 2012 thorough 2019.
The Baraba lowland and Kulunda plain are characterized by a rolling surface topography, which was produced by suffusion–deflation processes. The local
redistribution of moisture and its flow from watersheds to valleys between them (alternating parallel
southwest- to northeast-trending elongate topographic highs and depressions) has produced numerous lakes that filled the depressions. The territory is
made up of loess rocks ranging from heavy loams and
clays in the north to medium and light loams and
sandy loams in the south. The rocks contain 1 to 15%
carbonates (Syso, 2007). The lakes are hosted in modern Quaternary rocks, which are lacustrine–alluvial
loams with sand beds, alluvial sands, and lacustrine–
alluvial clays and loams (Explanatory Notes…, 1967).
It should be mentioned that the loess loams that are
widespread in Baraba and Kulunda and cover the
topographic highs as a layer 0.2 to 1.5 m, and more,
thick, are of wind-laid (aeolian) genesis, which has
significantly homogenized the granulometric and
chemical composition of the soil-forming rocks and
the soils themselves. For lacustrine sapropel, the soil
cover provides organo-mineral material and watersoluble salts, which are brought to lakes with surface
and soil-groundwaters and are accumulated at the
bottom of the lakes. The composition of the rocks and
soils predetermines the wide spread of waters of the
soda type over the whole territory. The composition of
rocks and soils in the catchments of the lakes was studied in much detail, and the results were summarized in
(Syso, 2007; Puzanov et al., 2016; Puzanov et al., 2017;
and others). The soils of the catchments and their geochemical features were studied along geochemical–
soil profiles across all of the major geomorphological
elements (flood plain, bench, and the watershed of the
lake basin), and soil profiles were sampled (from
selected soil horizons by Yu.V. Ermolov of the Institute
of Soil Science and Agrochemistry, Siberian Branch,
Russian Academy of Sciences) and A.V. Saltykov (of
the Institute of Water and Environmental Problems,
Siberian Branch, Russian Academy of Sciences). The
lakes studied in the Baraba lowland are constrained
mostly within the forest–steppe zone. The structure of
the soil cover in the catchments of the lakes is defined
by the following alternating soil types: boggy soil →
meadow–boggy soil → meadow soil → meadow–
chernozem soil → southern and ordinary chernozem →
gray wood soil. The quantity and quality of material
brought to the lakes depends on concentrations of
humic compounds, fine particles, and ions of soluble
compounds in the soil cover. The concentrations of
humic compounds in the upper parts of the soil profiles broadly vary even within a single catchment, and
the degree of their humification ranges from low
(0.9%) to high (8.3%). The soils are highly permeable
to water and have low water-raising and water-holding
capacities. According to their degree of salinization in
the catchments, all of the soils are classified into
unsalinized (southern and ordinary chernozems,
meadow sod–gley soils, meadow–boggy humous soils,
and typical forest ones), weakly salinized (solonized
meadow–chernozem, boggy humous–gley, meadow
humous, and meadow soddy soils), and highly salinized (meadow–boggy humous–gley soils). The pH
of the soil cover in the catchments broadly varies, from
weakly acidic in the upper parts of the meadow–soddy
soils in the vicinities of Tsybovo Lake to strongly alkaline in the lower part of the profile of the meadow–
chernozem solonized soils. Carbonates were identified
in all of the soil types, except only the gray woody soils
typical of the basin of Bol’shie Kaily Lake and occur
mostly in lower horizons. Soils in the catchments of
lakes in the Kulunda plain are typical of the steppe
landscape zone: they are salinized, contain little organic
matter, and are highly dense. The following soil types
occur in the territory: saline soils (sor-affected,
meadow, and meadow–boggy soils), meadow–steppe
salinized, meadow salinized soils near lakes, podzols
and iron-enriched soddy illuvial podzols in the ribbon forest subzone, and dark brown solonized soils (Puzanov
et al., 2016, 2017; Ovdina et al., 2016; and others). The
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(а)
Scale
100
0
200 km
795
(b)
Kamen’-na-Obi
Kyshtovka
da
lun
Severnoe
Ku
Slavgorod
Kulundinskoe L.
Vengerovo
Aleisk
Barabinsk
Tatarsk
Chiosoozernoe
Ubinskoe
Zdvinsk
Rubtsovsk
Kochki
Kupino
Zmeinogorsk
Krasnozerskoe
Karasuk
1
2
3
4
5
7
8
9
10
11
6
Sampling sites
of lake components
1
4
7
2
5
8
3
6
9
Fig. 1. (a) Schematic map of the grain-size composition of soils and soil-forming rocks in the Baraba lowland (Soils, 1966) and
(b) soil–geographic zoning of the Kulunda plain (Nikol’skaya, 1961) with the sampling sites of components of the lake systems.
(a) (1) Loess-like heavy loams and light powdery–silty clays; (2) loess-like heavy powdery and powdery–silty loams; (3) loesslike intermediate and more rare heavy silty–powdery loams; (4) silty–powdery heavy loams and more rare clays; (5) powdery–
silty and silty–powdery heavy loams and clays; (6) sandy–silty and silty–sandy heavy and intermediate loams; (7) intermediate
sandy–powdery and powdery–sandy loams; (8) intermediate and light silty–sandy and powdery–sandy loams; (9) light silty–
sandy loams and more rare sandy clays: (10) sandy clays; (11) cohesive sands. (b) (1) Brown soils; (2) southern chernozems;
(3) ordinary chernozems; (4) leached chernozems and gray forest soils; (5) sod–podzol soils of ancient forest terraces; (6) typical
chernozems; (7) podzolized chernozems and dark gray forest soils; (8) weakly developed mountainous–meadow soils; (9) chernozems of southern piedmonts.
location of the lakes in these areas is shown in schematic soil-cover and soil-forming rock maps published in (Nikol’skaya, 1961; Soils, 1966; Il’in and
Syso, 2001) (Fig. 1). It has been demonstrated in our
earlier publications that concentrations of natural
radionuclides in the soils of different type in the
southern West Siberia are similar in various landscape zones (Strakhovenko et al., 2010; Strakhovenko, 2011; Mel’gunov et al., 2011; Malikova
and Strakhovenko, 2017).
The authors have previously studied in much detail
the geochemistry of the sapropels (Strakhovenko et al.,
2014; Strakhovenko et al., 2016, Strakhovenko et al.,
2019; and others) and have determined that the
organic constituent of the sapropels shows a variable
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contribution of various biological species. X-ray powder diffraction (XRD) data indicate that the mineral
component of the soils is composed of a relatively
short list of dominant minerals: quartz, plagioclase,
potassic feldspar, micas, and calcite. The minor minerals are pyrite, hydromicas, chlorites, dolomite. The
accessory minerals are ilmenite, hematite, zircon,
monazite, magnetite, apatite, rutile, titanite, etc. Our
earlier studies at the same areas have shown that the
concentrations of silicon, an element contained in
quartz and other rock-forming silicates and in diatom
and macrophyte remnants, broadly vary. The Al, K,
and Na concentrations vary proportionally, which
likely suggests their common source (Strakhovenko
et al., 2014). Sedimentation rates in the small sapropel
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STRAKHOVENKO et al.
Density of 137Cs, fallouts, mCi/km2
0
20
40
60
80 100 150 200 250
24.08.56 Trajectory of the air currents carrying nuclear-blast
products that caused intense local radioactive fallouts
27
8
5 6 4
12.08.53 Date of the nuclear blast
400
Nuclear yield
Kemerovo
Novosibirsk
Kaf kaim
Platovka
Istimass
Novyi Vostok
Fedorovka
Makarovka
Vasil'chuki
Klyuchi
Tselinnyi
Sampling sites
of lacustrine
sapropel
Kani
Petukhi
Novovoznesenka
Novokormino
Barnaul
Severka
Zapadnyi Ugol
Ashigul’
Berezovskii
Poluimki
Pokrovka
Nevodnoe
Irkutskii
Nikolaevka
Rakity
Ust’-Kormikha
Mikhailovskoe
.49
29.08
32
24.08.5
27
Ust’-Volchikha
Bor-Forpost
Bastan
Gorno-Altaisk
Valovoi Kordon
20
40
60
mCi/km2
80
100
6
50
13.08.53
3000
Simonovo
Malinovoe
Kormikha
Chernokorovnikovo
Borisovka
Ozerno-Kuznetsovskii Leskhoz
Kuznetsovo L.
Bor-Kosobulak
Alekseevka
Malaya Shelkovka
Rakity
Bol’shaya Shelkovka
Korosteli 2
Mirnyi
Pavlovka
Uglovskoe
Kuibyshevo
Lyapunovo
Krugloe
10
(a)
(b)
0
10 20 30 40 km
Korosteli 1
Gor’koe
Shelrukha
Borisovka
48
8.53
12.0
400
89 Fig. 2. (a) Map of the density of 137Cs fallouts in southern West Siberia (based on original data of the authors) (Rikhvanov, 2009)
and (b) a map of the density of 137Cs fallouts in the bottom sediments of the lakes of the Tanatarskaya and Klyuchevskaya systems.
lakes in various areas in Siberia (data calculated using
the 210Pb and 137Cs isotopes) are 0.15–0.35 cm/year
(Strakhovenko et al., 2017).
With regard to various approaches to the systematics of sapropels (Korde, 1969; Lopotko, 1978; Shtin,
2005; Kurzo et al., 2010; and others), herein we view
sapropels as organic–mineral bottom sediments with
ash contents reaching 85%. Based on mineralogical–
geochemical and biogenetic data, we classified the
organic–mineral bottom sediments according to their
composition. The sapropels were subdivided into four
types according to their ash content: organogenic (less
than 30% ash), organic–mineral (30–50%), mineralorganic (50–70%), and mineralized (70–85%). Bottom sediments with >85% ash were classed with mineral silts (Shtin, 2005; Kurzo et al., 2010; and others).
The authors of the paper further classify all sapropel
types, except organogenic ones, based on the Si/Ca ratio
into three classes: silicon (Si > Ca); calcium (Ca > Si),
and mixed (Si ~ Ca). According to the dominant production type, the sapropels were subdivided into planktonic, macrophytic, and planktonic–macrophytic.
Radioactive fallouts occurred in the territory of
West Siberia during nuclear tests at the Semipalatisk
and Novaya Zemlya test areas. The map of nuclear
trails across West Siberia indicates that the Baraba and
Kulunda areas were affected mostly by the 1953 and
1954 nuclear tests (Selegei, 1997). The total annual
beta activity of fallouts in Kulunda in 1961–1963 was
605–1584 mCi/km2 (Robertus, 1993). We have compiled the greatest database of analytical parameters of
sapropels in the Baraba lowland and Kulunda plain.
The database comprises our own original data and literature materials published before 2018. In cooperation with a large team of researchers, the authors have
sampled an extensive territory in southern West Siberia and mapped the density of radiocesium pollution
of soils in the Baraba lowland and Kulunda plain,
which were published in (Rikhvanov, 2009; Malikova
and Strakhovenko, 2011; Mel’gunov et al., 2011; and
others). Figure 2 shows a map of the density of 137Cs
fallouts in soils in southern West Siberia [the map is
based on original data of the authors and was published in the monograph (Rikhvanov, 2009)] and a
map of the density of 137Cs fallouts in the bottom sapropel sediments in lakes of the Tanatarskaya and Klychevskaya systems of larger scale, which was con-
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structed by the authors for each lake system in the
Baraba lowland and Kulunda plain separately.
METHODS
Cores of bottom sediments, soil profiles, soilforming rocks, as well as samples of the waters and
dominant plant species, were collected in the course of
a fieldwork. Water samples for all analyses were taken
in compliance with the state standards GOST 31861,
2012. We have determined the variable physicochemical pars of the waters and bottom sediment. The genesis
of sapropel formed in the various lakes was identified in
samples of the primary sapropel-forming material
(phytoplankton, photosynthetic pigments, zooplankton, phytobenthos and phytoperiphyton, macrophytes, grass cuttings for the biomass, and geobotanical descriptions). The lakes significantly vary in their
degree and character of macrophyte development and
the production levels of the aquatic phytocenoses. The
fluxes of autochthonous organic matter into the lakes
vary from 3.2% in hypersaline Malinovoe Lake (in
which the sedimentation flux is dominated by allochthonous halite) to 84.2% (in lakes with an autochthonous type of material accumulation, such as Barchin,
Kachkul’nya, and other lakes) of the total mass of the
sedimentation flux. The maximum production and
destruction values were found in lakes with the massive development of blue-green algae. The samples
taken for gamma spectrometric analysis included the
dominant producers of organic matter in each of the
lakes. For example, lakes massively overgrown with
macrophytes were sampled for the dominant submerged plants (morass-weed Ceratophyllum, soldier
Stratiotes, and charophytes Chorales) or for semisubmerged plants (Phragmites). In lakes of fringing vegetation type, we analyzed a few samples of the dominant biomass, and the further calculations were carried out using the arithmetic means of these samples.
Soils were sampled, using a metal ring, throughout
the whole depth of the soil profile. Samples were taken
from each soil horizon with a sharpened metal ring
(82 mm in diameter and 50 mm high). Each individual
soil profile was continuously sampled through its
upper 30 cm by a ring, and then each of the genetic
horizons was sampled. This allowed us to determine
radiocesium activity in each horizon, which is particularly important for the identification of a sod horizon
and the upper part of the humus–accumulation horizon A, which are able to accumulated the highest
radiocesium amounts. The obtained values of the
specific radiocesium activity, expressed in Bk/kg,
were recalculated into pollution density in mCi/km2
(Malikova and Strakhovenko, 2011).
The thickness of the sapropel layers was determined using an acoustic depth finder. Cores of bottom
sediments were taken from a twin-hull boat, using a
cylindrical corer with a vacuum lock (designed and
manufactured at the Taifun Research and Production
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Company, Russia) 82 mm in diameter and 120 mm
long. Samples were then collected from each layer of
the bottom sediment cores, with the sampling sites
spaced 5 to 25 cm apart, depending on the composition, with the mineral silt sampled from the basins of
the lakes. All of the samples were analyzed for moisture and ash contents and for the composition of the
organic and inorganic constituents of the sapropel.
The morphology and phase composition of the bottom sediment samples of various classes were studied
under a TESCAN MIRA 3 (Tescan, Czech Republic)
scanning electron microscope equipped with an
OXFORD XMAX 450+ (Oxford Instruments, United
Kingdom) energy-dispersive spectrometer.
Natural radionuclides and radiocesium were determined by gamma spectroscopy, using gamma spectrometers with NaI(Tl) well-type scintillation crystals
200 × 200 and 150 × 150 mm. The masses of the analyzed samples were varied between 100 and 450 g.
The detection limits at mass analyses was evaluated at
1–3 Bq/kg. The accuracy and reproducibility of the
analyses were determined by replicate analysis of the
SA-1 and SI-1 standards and the BSILT (7126-94) reference standard sample of Baikal silt. The accuracy of
analyses for natural radionuclides was estimated by
comparing with analyses of IAEA standard reference
samples, and the analytical laboratory has previously
successively participated in the certification of these
samples. Replicate analyses of soil and bottom sediment samples were used to estimate the reproducibility: replicate analysis of every tenth sample was conducted in strict compliance with the analytical procedures. According to the results of statistical processing
of data on 70 bottom sediment samples that contained
75 to 25% organic matter and were analyzed by two or
more techniques, the deviations between the 226Ra
activity values were no greater than 15%, and those for
Th and K were 10%. Detailed descriptions of the analytical techniques can be found in (Gavshin et al.,
2004; Mel’gunov et al., 2011; Malikova and Strakhovenko, 2017).
To assay how much the sapropels comply with the
radiation−hygienical standards, we calculated the
total effective specific activity (As) caused by natural
radionuclides by the formula (with regard to the coefficients) As = АRa + 1.31 ATh+ 0.085 AK1 , where АRa, ATh,
and AK1 are the specific activities of the corresponding
radionuclides. The standardized values of the As values
of natural radionuclides are no higher than 300 Bq/kg,
and those for artificial radionuclides are no greater than
1 relative unit, which is assumed to be equal to the
global background value (GOST R 54519, 2011).
The analyses were conducted at the Analytical
Center for Multielemental and Isotope Research,
Siberian Branch, Russian Academy of Sciences. The
data on the specific activity of radiocesium were recalculated with regard to the radioactive decay as of the
2022
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STRAKHOVENKO et al.
Table 1. Statistical parameters of geochemical data on the specific activity (Bq/kg) of natural radionuclides and 137Cs in the
various components of lake systems in the Baraba lowland (52 lakes) and Kulunda plain (41 lakes)
Variables
Specific activity of Ra
Specific activity of Th
Specific activity of K
Total effective specific activity
Specific activity of 137Cs
Specific activity of Ra
Specific activity of Th
Specific activity of K
Total effective specific activity of
Specific activity of 137Cs
Specific activity of Ra
Specific activity of Th
Specific activity of K
Total effective specific activity of
Specific activity of 137Cs
Average
Minimum value Maximum value
Standard
deviation
Asymmetry Excess
29
19
438
89
20
Soil (2137 samples)
1
1
10
3
0
112
59
751
234
198
11
22
146
37
42
0.7
2.4
0.6
1.2
2.9
1.0
5.9
1.6
3.3
8.4
32
12
470
90
3
Biota (112 samples)
1
156
1
152
10
1720
2
264
0
24
28
18
432
62
6
2.0
5.0
1.0
1.2
2.1
5.2
35.4
0.1
0.8
4.0
26
15
248
66
12
Sapropel (3956 samples)
1
143
1
58
10
870
3
187
0
342
16
10
176
33
31
1.8
0.7
0.4
0.5
4.8
7.0
0.2
0.4
0.5
30.4
year 2010 and put into the database. The analytical
data were statistically processed, including the estimation of radionuclide distribution in the soils, sapropel
deposits, and biota, tests of hypotheses of the types of
the distributions, and the evaluation of the correlations, were done using the Statistica 8 software and
MS Excel application. Cluster analysis was applied to
graphically represent the grouping of the analytical
data on the whole set of the analyzed elements in the
bottom sediments and soils (Mikhail’chuk et al.,
2006). The calculations were conducted with a т × п
matrix (where п is samples of bottom sediments, biota,
and/or soils, and т is the number of factors or variables (Ca, Mg, Na, Al, Fe, Si, U(Ra), Th, and K). The
number of variables in the solutions was varied to identify stable relationships between variables and to
obtain stable groups of lakes. The calculations were
conducted for R analysis−factors (elements). The
metrics of R analysis is the correlation coefficient. The
solutions were presented in the form of dendrograms
of correlations between chemical elements within a
specified set of objects. The QGIS and ArcGIS program packages were applied to build models for the
layer by layer and areal distributions of the 137Cs
reserves (mCi/km2) and the total effective activity (As)
of natural radionuclides in the sapropels and soils in
the catchments for the lakes studied in the various lake
systems in the Baraba lowland and Kulunda plain. An
example is presented in Fig. 2.
RESULTS AND DISCUSSION
Considered together with preexisting dataset on the
soil profiles, the newly obtained materials on the sapropels, biomass, and waters in lakes in the Baraba lowland and Kulunda plain show that, in spite of the significant variations in the concentrations of U(Ra), Th,
and K in the datasets, the average values for the soil
profiles and bottom sediment columns vary relatively
insignificantly (Table 1). This fact obviously indicates
that the concentrations are unevenly distributed in the
soil-forming rocks, from which the elements are transferred first into the soils and then into the sapropels.
During the very first evolutionary stages of the lakes,
their bottom sediments were formed on a mineral
source material. The topographic features had then
not been completely shaped, and the surface topography of the catchments was actively formed by erosion.
The corresponding rocks make up the lowermost portions of bottom-sediment columns in small lakes in
West Siberia, and the thickness of this layer is commonly 2−6 cm (at the total thickness of the sediments
of 3 to 29 m). The system was equilibrated with time,
and the bulk of the sediment-forming material was
brought from the catchments into lakes by streaming
waters and air flows (allochthonous material), with
the authigenic organic and mineral material formed by
hydrobionts (autochthonous material). The concentrations of natural radionuclides in the soil profiles
correspond to those in the loess loams. We statistically
GEOCHEMISTRY INTERNATIONAL
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Number of observations
Number of observations
RADIOACTIVITY ASSESSMENT OF SAPROPEL SEDIMENTS IN SMALL LAKES
100
90
80
70
60
50
40
30
20
10
0
700
600
500
400
300
200
100
0
799
(а)
(b)
(c)
Histogram of: Ас
К-С d = 0.13385, p < 0.05, Lilliefors p < 0.01
Normal expectation
Histogram of: Ас
К-С d = 0.03047, p > 0.20, Lilliefors p < 0.05
Normal expectation
Histogram of: Ас
К-С d = 0.14512, p < 0.05, Lilliefors p < 0.01
Normal expectation
Ас
Soil
–50 0 50 100 150 200 250
Upper boundaries, x ≤ boundary
(d)
Histogram of: 137Сs
К-С d = 0.3462, p < 0.01, Lilliefors p < 0.01
Normal expectation
137
Сs
Soil
–50 0 50 100 150 200 250 300 350
Upper boundaries, x ≤ boundary
600
500
400
300
200
100
0
70
60
50
40
30
20
10
0
Ас
Sapropel
–50 0
50 100 150 200
Upper boundaries, x ≤ boundary
(e)
Histogram of: 137Сs
К-С d = 0.31472, p < 0.01, Lilliefors p < 0.01
Normal expectation
137
Сs
Sapropel
–50 0
50 100 150 200
Upper boundaries, x ≤ boundary
45
40
35
30
25
20
15
10
5
0
70
60
50
40
30
20
10
0
Ас
Biota
–50 0 50 100 150 200 250 300
Upper boundaries, x ≤ boundary
(f)
Histogram of: 137Сs
К-С d = 0.34108, p < 0.01, Lilliefors p < 0.01
Normal expectation
137
Сs
Biota
–5 0 5 10 15 20 25
Upper boundaries, x ≤ boundary
Fig. 3. Histograms of the total effective specific activity (As) (Bq/kg) of (a, b, c) natural radionuclides and (d, e, f) 137Cs in the
soils, sapropel, and biota.
processed geochemical data on concentrations of natural radionuclides and 137Сs in the soils, sapropel bodies, and biota. The results show that all of the radionuclides are characterized by a normal or lognormal distribution (Fig. 3). A lognormal distribution indicates
that the contribution of samples with an elevated radiation background was small.
were found. Inasmuch as waters in the territories are
mostly alkaline, this is favorable for high U mobility in
the form of uranyl−carbonate Na compounds (Evseeva and Perel’man, 1962; and others). In the reducing
environments of lakes with a stagnant hydrodynamic
regime, uranium that has been previously adsorbed on
colloid particles is reduced (Titaeva, 2005).
Concentrations of Th and K in the sapropels of the
lakes generally correspond to those in soils in the
catchments and are generally lower than in the soils.
Uranium concentrations in the bottom sediment of all
of the lakes are lower than or equal to those in soils in
the catchments of these lakes, with rare exceptions of
lakes in the steppe and taiga zones. The exceptions are
some soda lakes whose waters have high pH (>9), in
which U concentrations in the sapropels are higher.
The depletion of the sapropels in potassium is most
likely explained by its leaching from minerals and
organic matter in the sediments.
Analysis of components of the lakes for U, Th, and
K enabled us to compare the contributions of the specific activity of natural radionuclides in various landscape zones of southern West Siberia and the contribution of their total specific activity (Fig. 5). The values of As of the biota soils broadly vary but never
exceed 300 Bq/kg. The values obtained for the soils are
consistent with literature data on the natural radioactivity of rocks (Titaeva, 2000; Rikhvanov, 2009). The
total effective specific activity of natural radionuclides
(As) in the bottom sediments of all of the small lakes is
lower than in soils in the catchments and never exceeds
the standardized maximum value of 300 Bq/kg
(GOST R 54519, 2011). It is worth mentioning that the
As values of the sapropels generally only insignificantly
inherit features of the catchments, i.e., the soil-forming rocks. This is explained by the significant contribution of the biota to the As values, with this contribution broadly varying even for a single lake (dependence
on the species), from one lake to another within a single landscape zone, and from one landscape zone to
Cluster analysis of the concentrations of trace elements and radionuclides in the soil and bottom-sediment samples has demonstrated the strongest positive
correlations of Al with Si, Th, K, and Na, which are
strongly correlated with many trace elements that are
mostly contained in clastic minerals of the bottom
sediments, such as quartz, feldspars, micas, mafic silicates, and aluminosilicates (Fig. 4). No correlations
between U(Ra) and these elements (including Sr)
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STRAKHOVENKO et al.
(а)
1.0 0.8 0.6 0.4 0.2
Fe
V
Al
K
Ba
Na
Si
Ni
Cu
Cr
Th
Mn
Co
Zn
Cd
Pb
Hg
U
Mg
Sr
Ca
P
(b)
0 –0.2 –0.4 –0.6 –0.8 –1.0
1.0
0.8
0.6
0.4
Na
Th
Hg
K
Al
Si
Cr
Cu
Ni
Fe
P
Cd
Pb
Co
Zn
U
Mg
Sr
Ba
Ca
Mn
Cluster R
Silicon class
0.2
0
–0.2 –0.4 –0.6 –0.8 –1.0
Cluster R
Calcium class
(c)
1.0
Na
Mg
Sr
Ba
U
Ca
P
Al
Si
Fe
Ni
Co
Cu
Th
Cr
Zn
Cd
Pb
Hg
K
Mn
0.8
0.6
0.4
0.2
0
–0.2 –0.4 –0.6 –0.8 –1.0
Cluster R
Mixed class
Fig. 4. Dendrograms of correlations between chemical elements (R-cluster analysis) based on analytical data on the concentrations of major and trace elements (Si, Ca, Na, K, Al, Mg, Fe, Ti, P, Mn, Sr, Ba, Pb, Cd, V, Cu, Zn, Co, Ni, Cr, Hg, U, and Th)
in the distinct classes of the sapropels: (a) silicon, (b) calcium, and (c) mixed.
another. This is explained by the significant contribution of potassium, whose concentrations in the biomass are high, to the total specific activity. Relations
between the U, Th, and K concentrations and their
specific activity are reported in (Rikhvanov, 2009).
To comprehensively estimate the radiation state of
the sapropel deposits and the outlooks of their industrial use, we systematized our results on relations
between the ash contents of the sediments and the
total specific activity As of natural radionuclides in various water bodies of the lake systems in various landscapes (Fig. 6). No dependence of the As values on the
ash contents of the sediments were detected, i.e., further evidence was obtained that biogeochemical processes largely control the chemical composition of the
sapropels. Detailed data on the dependence of As values on the mineralogical composition of the samples
of sapropel of various classes led us to determine the
following. As expected, the minimum As values were
detected in the carbonate sapropels, which is
explained by that both calcite and dolomite practically
cannot adsorb trace elements and do not contain them
as admixtures, except only Sr, Mn, and Ba. Conversely, the occurrence of much micas and/or feldspars is the sapropels leads to an increase in the As values, because much potassium is contained in minerals
of the terrigenous fraction. A decrease in the Th, U,
and K concentrations in the sapropels of the lakes in
all landscape zones, and hence, a decrease in the As
values, is explained by the dilution of the sediments
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200
Taiga landscape
150
(Kyshtovskaya lake system)
50
0
0
ilo
vo
U
rm
an
no
Sh
e
ch
uc
h’
eP
Le
ne
Sh
vo
ch
uc
h’
eL
eK
D
an
ch
’
ab
Sh
ch
u
Ka
r
200
(Klyuchevskaya
lake system)
150
(central Baraba)
Ch
ul
Ba ym
r
Ka chin
m
ba
l
Ka a
Be ily
Ka rgul
za ’
to
Ya vo
rg
B ol’
Pe . Ka
sc ily
ha
n
Ch oe
ist
S oe
B. uet
Ku ok
r
Sa gan
rb
Bu aly
gr k
Ve isto
rk e
h
N nee
izh
ne
e
50
200
Steppe landscape
150
50
0
0
0
Soil
Biota
Ko
ro
s
ali
kh
elt
y
Zh
Pe
tu
M
e
ch
’
L.
Ku
re
kh
L.
tel
ev
sk
oe
B.
Ta
sso
Ly
r
ap
un
ik
ha
Sh
ub
a
Ba
lan
so
r
50
no
vo
Io e
dn
o
Ka e
ra
Ta tan
na
tar
Ta -6
na
ta
Ta r 4
na
tar
D
em 2
ki
n
Ru o
ble
v
Pr o
es
no
e
50
ov
oS
100
r’
100
ov
oP
100
Pe
tu
(Uglovskaya
lake system)
(Tanatarskaya lake system)
150
801
Forest–steppe landscape
150
100
200
Bq/kg
200
100
aly
k
Bq/kg
RADIOACTIVITY ASSESSMENT OF SAPROPEL SEDIMENTS IN SMALL LAKES
Bottom sediments
Fig. 5. Total effective specific activity of natural radionuclides (As, Bq/kg, per dry weight) in the soils, biota, and bottom sediments of lakes occurring in various landscape zones of the Baraba lowland and Kulunda plain. The names of the lakes are listed
along the X axis.
Lakes in the Baraba lowland
Lakes in the Kulunda plain
Kachkul’nya
Yargol’
Kusgan160
Peschanoe
Kr. Lyaga
140
Kaily
Khoroshee
120
B. Kaily
Kankul’
100
Bol. Chicha
Itkul’
Zhiloe
80
60
40
20
0
Presnoe
Balansor
Zalivnoe
M. Minzelinskoe
Chistoe
Tsybovo
Bil’gen’
Bugristoe
Suetok
Kazatovo
Zhiloe K.
Bol. Kurgan
Karagan
Chulym
Mostovoe
B. Tassor
Kurech’e
Sarbalyk
Kuklei
Barchin
Bergul’ Kambala
160
140
120
100
80
60
40
20
0
Rublevo
Petukhovo S.
Korostelevskoe
Zheltyr’
Petukhovo P
Malinovoe
Tanatar 6
Ash content
Demkino
Tanatar 4
Lyapunikha
Iodnoe
Shuba
Gor’koe
As
Fig. 6. Total effective specific activity of natural radionuclides (As, Bq/kg, per dry weight) and ash content of sapropels in lakes
in the Baraba lowland and Kulunda plain. Circled lake names indicate to lakes with high Ca concentrations in their sapropels.
with silica (quartz sand of aeolian genesis). Note that
the presence of fringing-type vegetation of macrophytes at the lakes also hampers the influx of minerals
of aeolian genesis into the sapropel deposits. We have
previously determined that the trace-element compoGEOCHEMISTRY INTERNATIONAL
Vol. 60
No. 8
sition of the lacustrine silts and soils in the steppe
landscapes of the small lakes are identical, and this led
us to hypothesize that the dominant sources of material for the bottom sediments of the lakes were particles
of soil that rests on loess loams, and the main transport
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802
STRAKHOVENKO et al.
(а)
Bq/kg
20
40
60
80
0
100
10
10
20
20
30
30
Depth, cm
Depth, cm
0
(b)
Bq/kg
40
50
60
70
80
137
Cs
Barchin
Bol. Kaily
Bugristoe
Zhiloe-K
Lenevo
20
40
60
80
100
40
50
Gor’koe
60
70
137
Presnoe
Cs
Rakity
80
Fig. 7. Vertical distribution of the specific activity of 137Cs (Bq/kg) in the profiles of sapropel bodies in lakes in the (a) Baraba
lowland and (b) Kulunda plain. The lakes differ in composition and have an uneven distribution of radiocesium. The type of
the symbols denotes the class of the sapropel body: squares correspond to the calcium class (Ca > Si), circles are the silicon
class (Si > Ca), and triangles mark the mixed class (Si ~ Ca).
agent was dust storms, which are widespread in southern West Siberia (Gavshin et al., 1999; Strakhovenko,
2011; and others).
In lakes with open shores (such as Zheltyr’, Shuba,
and Zhiloe K), high As values are caused by that the
sediments are rich in muscovite, although loams on
the shores contain only trace amounts of muscovite.
Similar to any mica mineral, muscovite forms platy
crystals (thin platelets and flakes), which can be readily transported by wind and can be brought from the
catchment areas.
It is worth mentioning that radiocesium activity in
the soils and sapropels is high and is sometimes much
higher than the background activity. Radioactive fallouts occurred in some areas in Baraba and Kulunda, as
well as the territory of West Siberia as a whole, and
soils and bottom sediments in these territories are still
contaminated with radiocesium. Our database on
137Cs activity, recalculated to the year 2010 with the
QGIS and ArcView program packages, were used to
develop detailed models for the areal distribution of
137Cs reserves (mCi/km2) of the lake systems in various
parts of the Baraba lowland and Kulunda plain and
soils at the catchments of these systems. This material
is generally consistent with our earlier maps, for example, the map of radiocesium reserves in the upper
humus−accumulation horizon of soils in the Novosibirsk and Altai territories (Ad) (Malikova et al., 2005;
Malikova and Strakhovenko, 2011; and others).
According to the character of the vertical distribution of 137Cs in the sapropel deposits of the lake sys-
tems, these systems can be classified into two major
types. One of these types of 137Cs distribution in sapropel deposits pertains to lakes with two or more peaks of
137Cs activity in the bottom sediments, with this activity decreasing both up and down the vertical sections
of the sapropel deposits (Fig. 7). Anomalously high
137Cs concentrations at deep levels of the sediments
provide evidence that the sediments were originally
contaminated by fallouts after nuclear tests starting
from 1949. They can be explained by the passage of
radioactive clouds over the lake systems and radioactive fallouts from these clouds. These lakes tend to be
spatially constrained to radioactive fallout trails and
are undoubtedly systems whose lakes were originally
contaminated (Selegei, 1997; Rikhvanov, 2009). The
sapropel deposits of these lakes are noted for an elevated radiocesium activity, which is twice or more
higher than the global background (34 mCi/km2 as of
2010). The density of global 137Cs fallouts in the midlatitudes of Siberia, recalculated to 2010, is according
to various evaluations (including those of the authors
of this paper) 34 to 53 mCi/km2 (0.9–1.5 kBq/m2)
(Chernyaga et al., 2012; and others).
A feature of the other type is the fact that radiocesium is enriched in the upper horizons, and its activity
gradually diminishes toward lower levels to a depth of
40−50 cm, where it approaches zero (Fig. 8). No 137Сs
was found in the silts at depths greater than 40−50 cm.
Our earlier studies have demonstrated that the depth
of 40−50 cm corresponds (according to the plot of
210Pb distribution) to the beginning of nuclear tests at
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RADIOACTIVITY ASSESSMENT OF SAPROPEL SEDIMENTS IN SMALL LAKES
20
0
(а)
Bq/kg
40
60
80
0
10
80
Tanatar-4
Kambala
20
Yargol’
30
Suetok
Bol. Kurgan
Tsybovo
50
Depth, cm
Kazatovo
40
Rublevo
Bol. Tassor
30
Lyapunikha
40
Zalivnoe
Kurich’e
50
Peschanoe
60
70
60
10
20
Depth, cm
20
(b)
Bq/kg
40
803
Zheltyr’
60
137
137
Cs
70
80
Cs
80
Fig. 8. Vertical distribution of the specific activity of 137Cs (Bq/kg) in the profiles of sapropel deposits in lakes in the (a) Baraba
lowland and (b) Kulunda plain. The lakes differ in composition and show a gradual radiocesium enrichment with decreasing
depth, starting at a depth of 40–50 cm. The type of the symbols denotes the class of the sapropel deposits: squares correspond to
the calcium class (Ca > Si), circles are the silicon class (Si > Ca), and triangles mark the mixed class (Si ~ Ca).
the Semipalatinsk test area (Strakhovenko et al., 2010;
Strakhovenko et al., 2017; and others). Such distributions were found in many of the lakes. This distribution is likely explained by that radionuclides were continuously redistributed at the bottom–water interface,
and this is associated with 137Cs influx from the catchment to lake with soil particles: the bulk of 137Cs is concentrated in the upper sod soil horizon even nowadays,
and the destruction of this layer leads to the release of
the radionuclides and their removal (Table 2). Only
the past two decades were marked by the equalization
and even a decrease in 137Cs addition to the bottom
sediment compared to earlier decades. The decrease in
the 137Cs activity in the uppermost horizon is controlled by the decrease in the concentration of the
radioisotope in the sod horizon of the soil because of
decay. This distribution type is thus related to the secondary redistribution of the “retained” reserves of soil
137Cs between the sinking remnants of the dead biomass and the new accumulation of radionuclides by
the rooted aquatic vegetation and benthos. If the soils
gradually release their artificial radionuclides as a
result of chemical and physical processes, these radionuclides are accumulated in the lakes, i.e., the primary
radioactive contamination of the lakes is overprinted
by effects of secondary processes.
For most sapropel deposits in the lakes, regardless
of their chemical composition, the contamination
level with 137Cs corresponds to the global background.
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Evidently, it is the heterogeneous distribution of
radiocesium in the soils and bottom sediments
(because of the uneven fallouts of atmospheric precipitation during the nuclear tests) that is the main reason
for that the 137Cs activity in the sapropels of the lakes is
not correlated with the location of the lakes in various
landscape zones. The local landscape environments
affect the erosion–accumulation processes and
lithochemical migration. Known facts indicate that
radiocesium can migrate from upper soil horizons
downward, but this has never been detected in any of
the studied soil profiles (Table 2) (Izrael’, 2005; Rikhvanov, 2009; and others).
The distribution of natural radionuclides over the
whole lengths of cores from the sapropel deposits is
practically homogeneous throughout the whole time
period in question and depends, unlike what is typical
of the soil profiles, mostly not only the composition of
the soil-forming rocks (Malikova and Strakhovenko,
2017; Strakhovenko et al., 2017) but also on the composition of the biomass of the organic constituents of
the sediment.
At some of the lakes, their fringing reed tussock
were found out to serve as reactive barriers, which
seem to be able to fix soil particles brought from the
shores (Ovdina et al., 2019). The reed tussock partly
adsorb dissolved uranium, potassium, and radiocesium species and accumulate them in the root parts of
the tussocks (the root systems of reedmace and reed).
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STRAKHOVENKO et al.
Table 2. Morphological structure and vertical distribution of 137Cs specific activity (Bq/kg) in genetically different soil horizons in the catchments of the lakes
137Сs, Bq/kg
137Сs, Bq/kg
Horizon
Depth
Horizon
Depth
Baraba lowland, Zhiloe Lake
Kulunda plain, Demkino Lake
Ordinary chernozem
Iron-rich illuvial sod-podzol
A
0–5 cm
54
О
0–2 cm
43
2–7 cm
27
A
5–10 cm
31
A1
7–12cm
12
A
10–16
9
A1
12–17 cm
2
AB
16–31 cm
0
A1
17–27 cm
0
B
31–54 cm
0
A 1A 2
27–35 cm
0
BC
>54 cm
0
A2 B 1
35–75 cm
0
Meadow-chernozem solonized soil
B1
0–6 cm
36
B2
75–104 cm
0
Ad
>104 cm
0
A
6–18 cm
12
B3
B
18–40 cm
0
Meadow solonchak soil
0–5 cm
54
BC
>40 cm
0
S1
5–8 cm
32
Boggy humous-gley soil
S1
0–5 cm
89
Abound
8–13
11
Ap
5–10 cm
36
Abound
13–18
0
Ap
10–15 cm
12
Abound
18–20 cm
0
Ap
15–20cm
0
AS2
20–35 cm
0
Ap
35–50 cm
0
C
20–24 cm
0
S2
>50 cm
0
C
>24 cm
0
S3
Tsybovo Lake
Malinovoe Lake
Meadow sod soil
Sor solonchak
0–5 cm
49
S1
0–5
24
Ad
5–10 cm
13
A
5–10 cm
15
S2
10–15 cm
4
A
10–15 cm
4
S2
15–20 cm
0
A
15–22 cm
0
S2
20–36
0
AC
22–37 cm
0
S3
36–47
0
C
>37 cm
0
S4
47–59
0
Mostovoe Lake
S4S5
>59 cm
0
Typical gray forest soil
S5
A
0–5 cm
22
Iodnoe Lake
A
5–10 cm
11
Iron–rich illuvial sod–podzol
0–5
17
A
10–15 cm
2
A1
5–10
7
A
15–22 cm
0
A1
10–15
2
AB
22–44 cm
0
A1
15–21
0
B
44–74 cm
0
A1
21–60
0
BC
>74 cm
0
A1A2
60–82
0
Bol’shie Kaily Lake
A2B1
>82 cm
0
Typical gray forest soil
B1
A
0–5 cm
38
Krasnovishnevoe Lake
5–10
21
Meadow–steppe solonized soil
0–5 cm
21
AB
10–15
3
A/
AB
15–20 cm
0
5–10 cm
4
A/
AB
20–31
0
10–15 cm
0
A/
B
>31 cm
0
15–20 cm
0
A/
Meadow sod soil
20–25
0
A//
Ad
0–17 cm
31
AB
25–30
0
30–35
0
A
17–40 cm
0
B1
35–40
0
C
>40 cm
0
B1
40–58
0
Peschanoe Lake
ABr
Meadow sod soil
BC
58–76
0
0–5 cm
42
С
>76 cm
0
Ad
0–10 cm
23
Sor solonchak
Ad
0–5 cm
24
A
10–15 cm
11
S1
5–10 cm
15
A
15–20 cm
3
S1
10–15 cm
4
AB
20–30 cm
0
S1
15–20 cm
0
AB
30–59 cm
0
S2
21–26
0
C
59–78 cm
0
S3
26–50
0
C
>78 cm
0
S4
GEOCHEMISTRY INTERNATIONAL
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No. 8
2022
RADIOACTIVITY ASSESSMENT OF SAPROPEL SEDIMENTS IN SMALL LAKES
805
Our data do not reveal any significant differences in
the accumulation and redistribution of radiocesium in
the cores of the sapropels of any type and class.
extraction from the bottoms of the lakes is necessary
for the rational management of the natural resources
and should maintain the balance of the lake systems.
CONCLUSIONS
The bottom sediments of the small lakes show a
total effective activity (As) no higher that the standardized limiting values of 300 Bq/kg (GOST, 2011). The
value of As of sapropel body of any one lake is controlled primarily by the mineralogical composition of
the sediment (which depends on biogeochemical processes in the water and in the uppermost layer of the
sediment), radiogeochemical characteristics of soils in
the catchment, and hence, also the underlying rocks,
and the presence of fringing macrophyte vegetation
around the lakes, which hampers the introduction of
the aeolian components of the terrigenous fraction of
dust storms.
The sapropel deposits of some of the lakes were
found out to include horizons whose 137Cs reserves are
twice or more higher than the global background
(32 mCi/km2 as of 2010). These lakes tend to be spatially constrained within the areal trails of radioactive
fallouts after nuclear tests in the Semipalatinsk Test
Area and undoubtedly belong to lake systems with primary contamination of both the water bodies and soils
in the catchments. If the soils gradually get rid of artificial radionuclides as a result of their decay, these
lakes accumulate the radionuclides, because their primary radioactive contamination is overprinted by secondary processes of transport from the catchments.
Anomalously high (peak) concentrations of 137Cs in
some depth intervals provide evidence of the primary
(starting in 1949) contamination of the sediments by
products of nuclear tests.
According to Article 19 of the Federal Law of Environmental Protection 7-FZ of January 10, 2002,
which postulates standards not only for the quality of
the environment but also for the permissible influence
on the environment at economic and other activities to
guarantee environmental safety, some horizons in the
sapropel deposits cannot be directly utilized because
of their contamination by artificial radiocesium. It is
necessary to decide whether the material of these horizons should be first diluted with material with a low
radiocesium activity (sand, sandy clay, etc.), or these
horizons with a high radiocesium activity, which are
normally no thicker than 10 cm, i.e., make up no more
than 1% of the total thickness of the sapropel deposits,
can be utilized directly.
If the sapropels are brought from the bottom of the
lakes, ecological problems of these lakes are simultaneously solved: silt deposition in the lake is terminated, and this drastically reduces the internal eutrophyzing load, ensures the sustainable functioning of
the natural ecological system, and prevents the degradation of the lakes. Scientifically grounded sapropel
FUNDING
GEOCHEMISTRY INTERNATIONAL
Vol. 60
No. 8
This work is done on state assignment of IGM SB RAS
with the financial support of the Ministry of Science and
Higher Education of the Russian Federation.
CONFLICT OF INTEREST
The authors declare that they have no conflicts of interest.
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Translated by E. Kurdyukov
2022