55
5.3 The “Solid Phase-Pore Solution” Distribution Coefficient
in Soil (K d )
К d coefficient is the ratio between activity concentrations of radionuclide in the
solid phase and pore solution of soil in the state of interphase equilibrium or near it:
K d Error ,
=
!
(1)
where A solid phase and A solution are activity concentrations of
238
U in solid phase and
pore solution after 3 weeks of moistening the calculated amount of distilled water
to the state of water saturation.
Taking into account the activity concentration of
238
U in the soil sample taken for
the preparation of pore solution and its water capacity (WC), the activity concentration of
238
U in the solid phase of the soil can be estimated, using formula (2):
K d Error ,
=
!
(2)
where A U (Bq kg
−1
), activity concentration of
238
U in absolutely dry soil; A solution
(Bq kg
−1
), activity concentration of
238
U in soil pore solution; and WC (%), water
capacity of the soil.
The activity of uranium in water-saturated soil containing m kg of solid phase is
equal to A U × M solid , where M solid is mass of solid phase of soil.
In the state of interphase equilibrium
A solid phase Error ,
=
!
(3)
where M solution is mass of soil pore solution,
M
WC M
solution
s olid
=
×
0 01
.
(4)
then
K d Error Error
= =
!
(5)
The K d coefficient can be considered as a parameter characterizing the soil’s ability to prevent redistribution of the radionuclide in terrestrial ecosystems. As the
coefficient K d increases, the soil’s barrier functions become stronger, and, accordingly, the mobility of the element in the soil decreases (Iskra and Bakhurov 1981).
The K d coefficients for
238
U in the (0–10)-cm layer of water-saturated soils are
given in Fig. 7.
As it is seen from the data received, the genetic type of soil significantly affected
the value of the K d coefficient. Among the mineral soils, the minimum coefficients
K d (166–282; average, 207; coefficient of variation, 20) were characteristic of sandy
Uranium and Its Distribution in Typical Belarusian Soils
5.3 The “Solid Phase-Pore Solution” Distribution Coefficient
in Soil (K d )
К d coefficient is the ratio between activity concentrations of radionuclide in the
solid phase and pore solution of soil in the state of interphase equilibrium or near it:
K d Error ,
=
!
(1)
where A solid phase and A solution are activity concentrations of
238
U in solid phase and
pore solution after 3 weeks of moistening the calculated amount of distilled water
to the state of water saturation.
Taking into account the activity concentration of
238
U in the soil sample taken for
the preparation of pore solution and its water capacity (WC), the activity concentration of
238
U in the solid phase of the soil can be estimated, using formula (2):
K d Error ,
=
!
(2)
where A U (Bq kg
−1
), activity concentration of
238
U in absolutely dry soil; A solution
(Bq kg
−1
), activity concentration of
238
U in soil pore solution; and WC (%), water
capacity of the soil.
The activity of uranium in water-saturated soil containing m kg of solid phase is
equal to A U × M solid , where M solid is mass of solid phase of soil.
In the state of interphase equilibrium
A solid phase Error ,
=
!
(3)
where M solution is mass of soil pore solution,
M
WC M
solution
s olid
=
×
0 01
.
(4)
then
K d Error Error
= =
!
(5)
The K d coefficient can be considered as a parameter characterizing the soil’s ability to prevent redistribution of the radionuclide in terrestrial ecosystems. As the
coefficient K d increases, the soil’s barrier functions become stronger, and, accordingly, the mobility of the element in the soil decreases (Iskra and Bakhurov 1981).
The K d coefficients for
238
U in the (0–10)-cm layer of water-saturated soils are
given in Fig. 7.
As it is seen from the data received, the genetic type of soil significantly affected
the value of the K d coefficient. Among the mineral soils, the minimum coefficients
K d (166–282; average, 207; coefficient of variation, 20) were characteristic of sandy
Uranium and Its Distribution in Typical Belarusian Soils