114
(Tananaev 2011). It was discovered in considerable concentrations in Earth material, oceans, the Earth mantle and meteorites. The half-life of
238
U is 4.49 × 10
9
years
(4.49 billion years), and it is an α-emitter with maximum energy of 4.7 MeV.
Environmental contamination by
238
U occurs in the resting places of rocks with
high uranium content in the points, where the ground waters come out on the Earth
surface.
238
U enters the atmosphere because of volcanic outbursts, meteoric dust and
soil transfer by the wind.
A significant fraction of environmental contamination is formed by the products
of
238
U leaching from the wastes of uranium mines and plants and releases of uranium fusion (yellow substance) from the stacks of the enterprises processing the
uranium concentrate. Entrance into the environment with the wastes of phosphate
industry (at phosphate rock processing), application of phosphoric fertilisers (superphosphate, precipitated phosphate and others), coil burning at thermal power plants
and primary metal establishments are considered as the intensive source of agrocoenosis contamination (Drichko 1983). The content of mobile forms of
238
U in ammophos and phosphogypsum comes up to 5.95% and 23% from gross content in
water-soluble form.
Uranium content in Earth crust is 2 × 10
−4
% (Tananaev 2011). The average content of
238
U in all Earth soils is 2.4 × 10
−4
% (Alexakhin 1982; Alexakhin and
Korneyev 1992). The
238
U content in grey forest soils is equal to 3.4 × 10
−4
%, in
chernozems—3.0 × 10
−4
%, and in the upper layers of sierozemic soils of semideserts, it comes up to 2.2 × 10
−4
%. The average content of
238
U in soils all over the
world is 24.4 Bq kg
−1
. Global technogenic flows of
238
U in biosphere were approximately 1.5 × 10
14
Bq at the operation of fuel cycle enterprises working on nuclear
and fossil fuels and 1 × 10
14
Bq at the application of phosphoric fertilisers.
238
U
amount in ploughing horizon of agricultural areas is 1.4 × 10
17
Bq (Alexakhin and
Korneyev 1992).
Uranium belongs to the class of water migrants, and in natural media, it exists in
(IV) and (VI) valency forms. In continental surface waters, the distribution of
238
U
follows the natural and climatic zone sequence, where the concentration of this
radionuclide varies from 10
−8
to 10
−5
g L
−1
. In the waters of large rivers flowing
through different climatic zones, the concentration of
238
U for the Northern
Hemisphere increases from north to south (Alexakhin et al. 1990).
In natural waters,
238
U exists as a uranyl ion UO
2 +
, which forms complex compounds with inorganic and organic acids. The ability of the uranyl ion to form complexes with ions such as SO 4
2−
, Cl
−
, F
−
, NO 3
−
, CO 3
−
, CH 3 COO
−
, etc. to become a
part of the negatively charged colloidal sols of the hydroxide and to form complexes
of uranium-organic compounds plays a major role in the migration of
238
U to natural
waters (Drichko 1983). The forms of
238
U in surface waters depend on pH and the
content of CO 2 and C org . In neutral and slightly acidic waters of the cold and temperate zones of the humid zone, the dissolved
238
U migrates in the form of fulvates,
hydroxy complexes or pseudocolloids. For weakly alkaline waters of the arid zone
containing carbonate ion, the main forms of finding
238
U are stable carbonate complexes [UO 2 (CO 3 ) 2 (H 2 O 2 ) 2 ]
2−
and [UO 2 (CO 3 ) 3 ]
4−
. The researchers also assume the
presence of bicarbonate complex compounds
238
U (Alexakhin et al. 1990).
A. N. Ratnikov et al.
(Tananaev 2011). It was discovered in considerable concentrations in Earth material, oceans, the Earth mantle and meteorites. The half-life of
238
U is 4.49 × 10
9
years
(4.49 billion years), and it is an α-emitter with maximum energy of 4.7 MeV.
Environmental contamination by
238
U occurs in the resting places of rocks with
high uranium content in the points, where the ground waters come out on the Earth
surface.
238
U enters the atmosphere because of volcanic outbursts, meteoric dust and
soil transfer by the wind.
A significant fraction of environmental contamination is formed by the products
of
238
U leaching from the wastes of uranium mines and plants and releases of uranium fusion (yellow substance) from the stacks of the enterprises processing the
uranium concentrate. Entrance into the environment with the wastes of phosphate
industry (at phosphate rock processing), application of phosphoric fertilisers (superphosphate, precipitated phosphate and others), coil burning at thermal power plants
and primary metal establishments are considered as the intensive source of agrocoenosis contamination (Drichko 1983). The content of mobile forms of
238
U in ammophos and phosphogypsum comes up to 5.95% and 23% from gross content in
water-soluble form.
Uranium content in Earth crust is 2 × 10
−4
% (Tananaev 2011). The average content of
238
U in all Earth soils is 2.4 × 10
−4
% (Alexakhin 1982; Alexakhin and
Korneyev 1992). The
238
U content in grey forest soils is equal to 3.4 × 10
−4
%, in
chernozems—3.0 × 10
−4
%, and in the upper layers of sierozemic soils of semideserts, it comes up to 2.2 × 10
−4
%. The average content of
238
U in soils all over the
world is 24.4 Bq kg
−1
. Global technogenic flows of
238
U in biosphere were approximately 1.5 × 10
14
Bq at the operation of fuel cycle enterprises working on nuclear
and fossil fuels and 1 × 10
14
Bq at the application of phosphoric fertilisers.
238
U
amount in ploughing horizon of agricultural areas is 1.4 × 10
17
Bq (Alexakhin and
Korneyev 1992).
Uranium belongs to the class of water migrants, and in natural media, it exists in
(IV) and (VI) valency forms. In continental surface waters, the distribution of
238
U
follows the natural and climatic zone sequence, where the concentration of this
radionuclide varies from 10
−8
to 10
−5
g L
−1
. In the waters of large rivers flowing
through different climatic zones, the concentration of
238
U for the Northern
Hemisphere increases from north to south (Alexakhin et al. 1990).
In natural waters,
238
U exists as a uranyl ion UO
2 +
, which forms complex compounds with inorganic and organic acids. The ability of the uranyl ion to form complexes with ions such as SO 4
2−
, Cl
−
, F
−
, NO 3
−
, CO 3
−
, CH 3 COO
−
, etc. to become a
part of the negatively charged colloidal sols of the hydroxide and to form complexes
of uranium-organic compounds plays a major role in the migration of
238
U to natural
waters (Drichko 1983). The forms of
238
U in surface waters depend on pH and the
content of CO 2 and C org . In neutral and slightly acidic waters of the cold and temperate zones of the humid zone, the dissolved
238
U migrates in the form of fulvates,
hydroxy complexes or pseudocolloids. For weakly alkaline waters of the arid zone
containing carbonate ion, the main forms of finding
238
U are stable carbonate complexes [UO 2 (CO 3 ) 2 (H 2 O 2 ) 2 ]
2−
and [UO 2 (CO 3 ) 3 ]
4−
. The researchers also assume the
presence of bicarbonate complex compounds
238
U (Alexakhin et al. 1990).
A. N. Ratnikov et al.