34
1 Introduction
Uranium belongs to terrigenous radionuclides and is relatively widespread in nature.
In notable concentrations, it is found in many rocks and oceans. Uranium is mainly
in a diffuse state, and its content in different parts of the Earth is not the same.
According to the prevalence in the Earth’s crust, uranium occupies the 38th place.
The average content of uranium in the Earth’s crust is 2.3 × 10
−4
(wt. %) that higher
than content of silver, bismuth, cadmium, and mercury. It is believed most of the
uranium is concentrated in the Earth’s crust and is not distributed evenly throughout
the planet substance (Greenwood and Earnshaw 1997).
The content of uranium in the Earth’s soils varies in the range of 0.7–10.7 μg kg
−1
(Kabata-Pendias and Pendias 1989). In the upper horizons of the Russian Plain
soils, the concentration of uranium is in the range of 0.7–1.8 μg kg
−1
(Vinogradov
1950). The oceans contain about 10
10
tons of uranium, and the average concentration of uranium in seawater is 3.3 μg L
−1
. In the surface waters, it is in the range of
0.01–5 μg L
−1
and in groundwater 0.1–500 μg L
−1
(Ivanovich and Harmon 1982).
Radionuclides of natural radioactive uranium series play an important role in the
formation of a dose load of the population living in territories with a normal radiation background. Their contribution to the effective dose of internal human irradiation from alpha-emitting radionuclides of the Earth’s crust is substantial (Vasilenko
2001; GN 2.6.1.8–27-2000 Radiation safety standards 2002; IAEA 2004). In this
connection there is a need for information on the content of uranium in the components of the environment, from where it can enter the human body.
The most important elements of natural systems that have a significant effect on
the redistribution of uranium in the biosphere are soil and natural waters. Therefore,
data on the content of uranium in soil and soil waters are of interest.
The study of background levels of uranium content in the soil-plant complexes
of Belarus is still at the initial stage. The main part of the available information on
that problem is obtained in the 1950–1980s of the twentieth century and concerns
the distribution of
238
U in soils, depending on the composition and landscapegeochemical conditions of the distribution of soil-forming rocks (Shagalova 1986;
Gurskiy and Loseva 1989; Kuznetsov 1997; Lukashov 2002). In recent years, the
results on behavior of natural uranium in forest biogeocenoses of the Minsk Upland
were published (Anisova and Yakushev 2008).
Migration of any element from the soil to plants is mainly carried out in the
forms in which they are present in interstitial (pore) solutions of soils in the area of
root nutrition of plants. In soil pore solution, radionuclides are present in forms
characterized by the highest capacity for geochemical and biological migration
(Ovsiannikova et al. 2000). That is why information on the content of radionuclides
in pore solutions of soils and on the stock of radionuclides in soils in the forms, in
which they can enter into the soil waters, is of particular interest.
The increase in the technogenic load on ecosystems, which has increased significantly since the mid-twentieth century, including the widespread use of mineral
fertilizers in agriculture, leads to changes in soil properties, content, physicochemical
statе, and mobility of radionuclides in soils. This can lead to a redistribution of
G. A. Sokolik et al.
1 Introduction
Uranium belongs to terrigenous radionuclides and is relatively widespread in nature.
In notable concentrations, it is found in many rocks and oceans. Uranium is mainly
in a diffuse state, and its content in different parts of the Earth is not the same.
According to the prevalence in the Earth’s crust, uranium occupies the 38th place.
The average content of uranium in the Earth’s crust is 2.3 × 10
−4
(wt. %) that higher
than content of silver, bismuth, cadmium, and mercury. It is believed most of the
uranium is concentrated in the Earth’s crust and is not distributed evenly throughout
the planet substance (Greenwood and Earnshaw 1997).
The content of uranium in the Earth’s soils varies in the range of 0.7–10.7 μg kg
−1
(Kabata-Pendias and Pendias 1989). In the upper horizons of the Russian Plain
soils, the concentration of uranium is in the range of 0.7–1.8 μg kg
−1
(Vinogradov
1950). The oceans contain about 10
10
tons of uranium, and the average concentration of uranium in seawater is 3.3 μg L
−1
. In the surface waters, it is in the range of
0.01–5 μg L
−1
and in groundwater 0.1–500 μg L
−1
(Ivanovich and Harmon 1982).
Radionuclides of natural radioactive uranium series play an important role in the
formation of a dose load of the population living in territories with a normal radiation background. Their contribution to the effective dose of internal human irradiation from alpha-emitting radionuclides of the Earth’s crust is substantial (Vasilenko
2001; GN 2.6.1.8–27-2000 Radiation safety standards 2002; IAEA 2004). In this
connection there is a need for information on the content of uranium in the components of the environment, from where it can enter the human body.
The most important elements of natural systems that have a significant effect on
the redistribution of uranium in the biosphere are soil and natural waters. Therefore,
data on the content of uranium in soil and soil waters are of interest.
The study of background levels of uranium content in the soil-plant complexes
of Belarus is still at the initial stage. The main part of the available information on
that problem is obtained in the 1950–1980s of the twentieth century and concerns
the distribution of
238
U in soils, depending on the composition and landscapegeochemical conditions of the distribution of soil-forming rocks (Shagalova 1986;
Gurskiy and Loseva 1989; Kuznetsov 1997; Lukashov 2002). In recent years, the
results on behavior of natural uranium in forest biogeocenoses of the Minsk Upland
were published (Anisova and Yakushev 2008).
Migration of any element from the soil to plants is mainly carried out in the
forms in which they are present in interstitial (pore) solutions of soils in the area of
root nutrition of plants. In soil pore solution, radionuclides are present in forms
characterized by the highest capacity for geochemical and biological migration
(Ovsiannikova et al. 2000). That is why information on the content of radionuclides
in pore solutions of soils and on the stock of radionuclides in soils in the forms, in
which they can enter into the soil waters, is of particular interest.
The increase in the technogenic load on ecosystems, which has increased significantly since the mid-twentieth century, including the widespread use of mineral
fertilizers in agriculture, leads to changes in soil properties, content, physicochemical
statе, and mobility of radionuclides in soils. This can lead to a redistribution of
G. A. Sokolik et al.