60
an increase in temperature from +15 to +30 °C could be caused by a change in the
structure of the surface of soil aggregates, and to a greater extent was characteristic
of peaty soil.
Change in the content of U mob in water-saturated soil samples at varying
temperature conditions. In the water-saturated sod-podzolic soil, the activity
concentration of U mob was in the range from (2.5 ± 0.2) to (0.9 ± 0.2) Bq kg
−1
of
solid matter, and the fraction of U mob was from (7.2 ± 0.7) to (2.6 ± 0.4)% of the total
uranium content in the soil. In the water-saturated peaty soil, the activity concentration of U mob varied from (0.64 ± 0.07) to (2.5 ± 0.2) Bq kg
−1
, and the fraction of U mob
was from (22 ± 2) to (5.5 ± 0.7)%.
Data on the variation with the temperature of the fraction U mob in soils in the
temperature range from −18 to +30 °C are given in Fig. 9.
In both water-saturated soils, the fraction of U mob decreased with increasing temperature in the entire studied temperature range (from −18 to 30 °C). In peaty soil,
the portion of U mob declined by a factor of 4, and in sod-podzolic light loam soil by
a factor of 2.8.
The decrease with increasing temperature of the fraction of U mob in watersaturated soils could be associated with a change in the oxidation-reduction conditions with increasing temperature as a result of a decrease in the oxygen content in
the water-filled soil pore space. Under these conditions, partial reduction of U (VI)
to U (IV) by humic substances of the soil was possible. The degree of reduction
could increase with increasing temperature. The compounds of U (IV) have a lower
solubility in water than U (VI) compounds, which could be the reason for the
Fig. 8 The portions U mob in air dry samples of sod-podzolic light loamy (SP) and peaty (T) soils
after their aging at different temperatures
G. A. Sokolik et al.
an increase in temperature from +15 to +30 °C could be caused by a change in the
structure of the surface of soil aggregates, and to a greater extent was characteristic
of peaty soil.
Change in the content of U mob in water-saturated soil samples at varying
temperature conditions. In the water-saturated sod-podzolic soil, the activity
concentration of U mob was in the range from (2.5 ± 0.2) to (0.9 ± 0.2) Bq kg
−1
of
solid matter, and the fraction of U mob was from (7.2 ± 0.7) to (2.6 ± 0.4)% of the total
uranium content in the soil. In the water-saturated peaty soil, the activity concentration of U mob varied from (0.64 ± 0.07) to (2.5 ± 0.2) Bq kg
−1
, and the fraction of U mob
was from (22 ± 2) to (5.5 ± 0.7)%.
Data on the variation with the temperature of the fraction U mob in soils in the
temperature range from −18 to +30 °C are given in Fig. 9.
In both water-saturated soils, the fraction of U mob decreased with increasing temperature in the entire studied temperature range (from −18 to 30 °C). In peaty soil,
the portion of U mob declined by a factor of 4, and in sod-podzolic light loam soil by
a factor of 2.8.
The decrease with increasing temperature of the fraction of U mob in watersaturated soils could be associated with a change in the oxidation-reduction conditions with increasing temperature as a result of a decrease in the oxygen content in
the water-filled soil pore space. Under these conditions, partial reduction of U (VI)
to U (IV) by humic substances of the soil was possible. The degree of reduction
could increase with increasing temperature. The compounds of U (IV) have a lower
solubility in water than U (VI) compounds, which could be the reason for the
Fig. 8 The portions U mob in air dry samples of sod-podzolic light loamy (SP) and peaty (T) soils
after their aging at different temperatures
G. A. Sokolik et al.