183
2.2 Hydroponic Experiment
Experiments were conducted using 3 L beakers, which were divided into six groups,
including five experimental groups (A, B, C, D, and E) and one control group (F).
The UO 2 (NO 3 ) 2 ·6H 2 O was added into each experimental group, and its initial uranium concentration was set at 2 mg L
−1
. The experiments were conducted in triplicate. Each beaker in all groups contained 3 g of Azolla-Anabaena and 1 L Hoagland
nutrient solution. The pH values of groups A, B, and C were adjusted to 4.0, 6.5, and
10.5, respectively, by HCl and NaOH. A 10 mM Na 2 CO 3 and 1 mM K 2 HPO 4 were
added into groups D and E, respectively. The beakers for experiments were put into
the climate box. The temperature was set at 25 °C during the day and 22 °C during
the night, and the air humidity was maintained at 80%. The day and night ratio was
set at 12:12. The uranium contents and their removal rates were measured every 3
days. The fresh weights were analyzed after 15 days, and the growth inhibition rates
(G) were calculated using the following formula:
G g g g
=
−
(
) ×
0
1
0 100
/
%
(1)
where G is the growth inhibition rate (percent), g 0 is the fresh weight of the
Azolla- Anabaena in the control group (g), and g 1 is the fresh weight of the AzollaAnabaena in the experimental group (g).
2.3 Preparation of Different Species of Uranium
Visual MINTEQ 3.1 Software
The proportions of different species of uranium in solutions under different conditions were calculated with MINTEQ 3.1 software. In a typical experimental process, once Visual MINTEQ is started, the main menu will appear. Then, change the
pH option to “Fixed at,” and make sure that the value in the text box is 4.0. The ionic
strength option should be “To be calculated,” since it is the default option. The concentration unit should be mg L
−1
, and the temperature is given as 25 °C. Then add
the component, U(VI), with a concentration of mg L
−1
. Next, click “Run” to calculate the proportions of different species of uranium.
Preparation of UO 2
2+
, (UO 2 ) 3 (OH) 5
+
, and UO 2 (OH) 3
−
In order to confirm the experimental conditions needed for different species of uranium and the proportions of different species of uranium in solutions at different pH
levels, carbonate and phosphate concentrations were calculated by Visual MINTEQ
3.1 software, which were calculated by the software when the initial uranium concentration was 2 mg L
−1
(Fig. 1). As shown in the figure, the main species of
Influence of Uranium Speciation on Plant Uptake
2.2 Hydroponic Experiment
Experiments were conducted using 3 L beakers, which were divided into six groups,
including five experimental groups (A, B, C, D, and E) and one control group (F).
The UO 2 (NO 3 ) 2 ·6H 2 O was added into each experimental group, and its initial uranium concentration was set at 2 mg L
−1
. The experiments were conducted in triplicate. Each beaker in all groups contained 3 g of Azolla-Anabaena and 1 L Hoagland
nutrient solution. The pH values of groups A, B, and C were adjusted to 4.0, 6.5, and
10.5, respectively, by HCl and NaOH. A 10 mM Na 2 CO 3 and 1 mM K 2 HPO 4 were
added into groups D and E, respectively. The beakers for experiments were put into
the climate box. The temperature was set at 25 °C during the day and 22 °C during
the night, and the air humidity was maintained at 80%. The day and night ratio was
set at 12:12. The uranium contents and their removal rates were measured every 3
days. The fresh weights were analyzed after 15 days, and the growth inhibition rates
(G) were calculated using the following formula:
G g g g
=
−
(
) ×
0
1
0 100
/
%
(1)
where G is the growth inhibition rate (percent), g 0 is the fresh weight of the
Azolla- Anabaena in the control group (g), and g 1 is the fresh weight of the AzollaAnabaena in the experimental group (g).
2.3 Preparation of Different Species of Uranium
Visual MINTEQ 3.1 Software
The proportions of different species of uranium in solutions under different conditions were calculated with MINTEQ 3.1 software. In a typical experimental process, once Visual MINTEQ is started, the main menu will appear. Then, change the
pH option to “Fixed at,” and make sure that the value in the text box is 4.0. The ionic
strength option should be “To be calculated,” since it is the default option. The concentration unit should be mg L
−1
, and the temperature is given as 25 °C. Then add
the component, U(VI), with a concentration of mg L
−1
. Next, click “Run” to calculate the proportions of different species of uranium.
Preparation of UO 2
2+
, (UO 2 ) 3 (OH) 5
+
, and UO 2 (OH) 3
−
In order to confirm the experimental conditions needed for different species of uranium and the proportions of different species of uranium in solutions at different pH
levels, carbonate and phosphate concentrations were calculated by Visual MINTEQ
3.1 software, which were calculated by the software when the initial uranium concentration was 2 mg L
−1
(Fig. 1). As shown in the figure, the main species of
Influence of Uranium Speciation on Plant Uptake