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Uranium migration in a podzol. The role of colloids in the non-saturated zone and the phreatic water: application to the Landes de Gascogne area; Migration de l'uranium dans un podzol. Le role des colloides dans la zone non saturee et la nappe: application aux Landes de Gascogne

Abstract

The non-saturated zone of a soil represents the interface between the atmosphere and the phreatic water. The confinement efficiency of the non-saturated zone above the phreatic water depends on the fastness of water transfers and on the type of pollutant transport mechanisms. Uranium (VI) can combine with humid acids to form very stable complexes. The aggregates of the absorbing complex are highly sensible to the variations of the ionic force of the environment. This sensitiveness can be at the origin of a strong remobilization of the colloid humic compounds of the soil, and of their migration towards the underground water. In this situation, the uranium complexed by humic compounds can rapidly migrate in the soil. The comparative reactive transport of the total uranium and its isotopes has been studied in a site, the Landes de Gascogne podzol (SW France), where metallic uranium has been sprinkled on the surface of the soil. The field study has been completed with an experimental column transport study using uranium isotopes tracer techniques. The field study shows that most of uranium is trapped in the very first cm of the soil. However, anomalous high uranium concentrations are observed in underground waters, more than 2 km  More>>
Authors:
Publication Date:
Jan 01, 2001
Product Type:
Thesis/Dissertation
Report Number:
FRCEA-TH-820
Resource Relation:
Other Information: TH: These sciences de la terre et de l'univers; [190 refs.]; PBD: Jan 2001
Subject:
54 ENVIRONMENTAL SCIENCES; AQUIFERS; CLAYS; COLLOIDS; GEOCHEMISTRY; HUMIC ACIDS; HYDROLOGY; PH VALUE; RADIONUCLIDE MIGRATION; SOIL CHEMISTRY; TRACER TECHNIQUES; TRAPPING; URANIUM; URANIUM COMPLEXES
OSTI ID:
20209203
Research Organizations:
CEA Bruyeres le Chatel, Lab. d'Hydrogeochimie et Etudes de Sites, 91 (France); Universite Joseph Fourier, Grenoble I, 38 (France)
Country of Origin:
France
Language:
French
Other Identifying Numbers:
TRN: FR0107656062144
Availability:
Available from INIS in electronic form
Submitting Site:
FRN
Size:
284 pages
Announcement Date:

Citation Formats

Crancon, P. Uranium migration in a podzol. The role of colloids in the non-saturated zone and the phreatic water: application to the Landes de Gascogne area; Migration de l'uranium dans un podzol. Le role des colloides dans la zone non saturee et la nappe: application aux Landes de Gascogne. France: N. p., 2001. Web.
Crancon, P. Uranium migration in a podzol. The role of colloids in the non-saturated zone and the phreatic water: application to the Landes de Gascogne area; Migration de l'uranium dans un podzol. Le role des colloides dans la zone non saturee et la nappe: application aux Landes de Gascogne. France.
Crancon, P. 2001. "Uranium migration in a podzol. The role of colloids in the non-saturated zone and the phreatic water: application to the Landes de Gascogne area; Migration de l'uranium dans un podzol. Le role des colloides dans la zone non saturee et la nappe: application aux Landes de Gascogne." France.
@misc{etde_20209203,
title = {Uranium migration in a podzol. The role of colloids in the non-saturated zone and the phreatic water: application to the Landes de Gascogne area; Migration de l'uranium dans un podzol. Le role des colloides dans la zone non saturee et la nappe: application aux Landes de Gascogne}
author = {Crancon, P}
abstractNote = {The non-saturated zone of a soil represents the interface between the atmosphere and the phreatic water. The confinement efficiency of the non-saturated zone above the phreatic water depends on the fastness of water transfers and on the type of pollutant transport mechanisms. Uranium (VI) can combine with humid acids to form very stable complexes. The aggregates of the absorbing complex are highly sensible to the variations of the ionic force of the environment. This sensitiveness can be at the origin of a strong remobilization of the colloid humic compounds of the soil, and of their migration towards the underground water. In this situation, the uranium complexed by humic compounds can rapidly migrate in the soil. The comparative reactive transport of the total uranium and its isotopes has been studied in a site, the Landes de Gascogne podzol (SW France), where metallic uranium has been sprinkled on the surface of the soil. The field study has been completed with an experimental column transport study using uranium isotopes tracer techniques. The field study shows that most of uranium is trapped in the very first cm of the soil. However, anomalous high uranium concentrations are observed in underground waters, more than 2 km away from the contaminated areas. This demonstrates that a fast and long distance transport process exists for uranium in the unsaturated zone. In the sandy soil of the study area, natural argillo-humic colloids migrate with the velocity of water but can be delayed when the ionic force of the underground waters increases. It is shown that uranium is strongly linked with the thin grain size fraction (< 8 {mu}m) of the sand, and more particularly with the argillo-humic composite colloids. In the stable geochemical conditions of the experimental columns, more than 70% of uranium is trapped in the first 2 cm of the sand, even after the circulation of 100 volumes of water inside the column. This shows the strong trapping capacity of the Landes sand. The addition of natural colloids to the injected solution favors the migration of uranium. Between 5 and 15% of the total uranium input is transported by argillo-humic colloids at water speed. The use of {sup 233}U allows to discriminate between the uranium transported through the sand in a non-reactive way, and the uranium desorbed from the argillo-humic aggregates and the sand grain coatings. A fast reduction of the ionic force of the environment during the tests shows an important remobilization of uranium from the soil. When the complex relations between hydrology and geochemistry in the unsaturated zone are considered, it appears that uranium transport is controlled: by the ionic force and pH value disturbances as an answer to rain water infiltration or phreatic water rises, and by the existence of an acidity and dissolved oxygen stratification in the soil which determines the speciation of uranium and the efficiency of sorption at the surface of soil minerals and colloids above the free surface of the phreatic water. (J.S.)}
place = {France}
year = {2001}
month = {Jan}
}