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mobile uranium(iv)-bearing colloids in a mining-impacted wetland

by:Top-In     2020-08-06
It is generally believed that the four-valent uranium forms a refractory species, resulting in uranium being fixed under reduction conditions.
Here we introduce mobile U (IV)-
The general assumption of carrying a gel in the environment is questioned.
We study the mobility of uranium in mining.
Affected wetlands in France have a uranium concentration of up to 14,000. p. m.
Since it is possible to observe the obvious release of uranium into streams passing through the wetland, we studied the composition of soil and porewater as a function of depth to assess the geophysical conditions leading to such release.
Analysis shows that U exists (IV)
As non in soil
Crystal species bound with amorphous Al-P-Fe-
Si is a unique species associated with Fe and organic colloid, as well as in porewater.
These results prove that U (IV)
In these soils, it is associated with a moving porewater gel that is eventually released into surface water.
The stream flowing through the wetland is shallow and the maximum depth is about 20 cuccm.
Sample the stream water from a depth of about 10 cuccm.
Samples were taken in different locations in April, November 2011 and July 2012, each of which was divided into two parts, one with pH (
Multi-parameter instruments using WTW multi-50i or HORIBA W20)
And alkaline (
HACH titration box with sulfuric acid and methyl bromide Green/a red color indicator)
Another filter with 0. 22u2009μm pore-
Poly (size)PES)
The membrane and U content were analyzed using inductive coupled plasma mass spectrometry on the thermal X7 analyzer (
Test limit of U: 4. 2u2009nM).
PH and alkaline values were reported in and U concentration was shown.
The stream was also sampled near position 3, using 0 filtering. 22u2009μm pore-
Enlarge the PES film and dry at 100 °c to obtain the powder.
Part of the powder is three-
Step HNO/HF Microwave digestion procedure for high-
Performance microwave, and then the emission spectrum using an inductive coupled plasma (ICP-OES)
For the main elements and U content, the mineral analysis of the other part was performed using X-ray diffraction.
The results are displayed in the main text and in.
Soil and porewater sampling activities were carried out in November 2011 and July 2012.
The soil core samples were collected only in November 2011, and porewater was collected in November and July to capture seasonal changes.
The core is high-
Flow Ar flow, sealed in a closed sterile bag, and then adjusted in the hypoxia chamber (N atmosphere)
5 min from sampling point.
Collect the vertical soil core with a Russian reel machine, cut into 5 cm slices, and each piece is divided into two parts, one of which is sealed in 0. 127-mm-thick (0. 005 inches)
MYLAR bag, stored at 4 °c for XAS analysis, the other is dried by heating at 80 °c for 24 hours in the hypoxia chamber, then ground and homogenized into powder for remaining analysis.
Using multi-sampling, sampling porewater with a vertical resolution of 5 cuccm
A cavity pressure gauge designed and manufactured in EPFL.
The concept of pressure gauge is.
The pressure gauge was installed at point A and point B on April and June 2011, respectively, with the help of A clay machine.
Porewater in each chamber uses LAMBDA high-flow peristaltic pumps and Tygon R-pumps to the surface
3603 pipe and measure the pH and DO of porewater using air-tight flow
By customizing cells for probes on EPFL.
And then in a high-
Flow Ar flow, sealed in a serum bottle with a blue scorpion plug, and then treated in an hypoxia chamber (N atmosphere)
5 min from sampling point.
Filter the sample with 0 in the hypoxia chamber. 22u2009μm pore-
The PES membrane is enlarged and divided into three parts: one with hypoxia 2 u2009 M HCl (
Volume ratio 1:1)for Fe(II)
Analysis, with 5 u2009 m HNO (
Volume ratio 1:5)
For metal ion analysis, the rest are stored in a serum bottle sealed with a Ding glue plug for the rest of the analysis. The Fe(II)
The concentration in pork samples was determined using the iron-zinc titration method described by ookey.
Solution of iron and zinc3-(2-pyridyl)-5,6-bis(4-
At pH 7, prepared in 1 gg l in 50 hemm HEPES. 0.
The porewater sample was analyzed by mixing the 15 μ l sample with 1,485 μ l iron and zinc solution.
UV-determination of absorbance at 562 µnm by Shimadzu
2501 PC light meter.
Using ICP-the concentration of metal ions in the porewater sample was obtained
Agarwood on Shimizu ICPE9000 analyser (
The detection limits of Fe and U: 1. 8 and 21u2009nM).
The ion concentration was measured using Dionex ICS 3000 ion chromatography.
Dissolved organic carbon and dissolved inorganic carbon (bicarbonate)
TOC-analysis of moisture in pork using ShimadzuAnalyzer 5000 (
Detection limit: 16. 7u2009μM).
Samples for LFS analysis at EPFL at H/N (3–4% H)anoxic chamber.
Water samples from two point a in November (
15-20 and 35-40 cm)
From July (15–20u2009cm)
Select LFS analysis.
Only dissolved U can be detected by LFS (VI).
Each sample is divided into two sub-samples of 4 ml using N-of 1 ml-
Purifying hypoxia 1m HCl and releasing U from Fe-rich colloids.
The previous test shows no U (VI)
If it is combined with Fe, it can be detectedrich colloids.
Prior to the analysis, one sub-sample was sealed in a serum-like bottle with a plug-in, and the other was exposed to air for at least 24 hours to oxidized U (IV)to U(VI).
Samples are then sent to HZDR for analysis.
Upon arrival, open the serum bottle containing the sample of hypoxia in the glove box (Braun, Germany)
The atmosphere is N (
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