Uranium facilitated transport by water-dispersible colloids in field and soil columns
Water Pollutants, Radioactive
550
[SDE.MCG]Environmental Sciences/Global Changes
Field monitoring
Fresh Water
Chemical Fractionation
01 natural sciences
Soil
[SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry
[SDU.STU.GC] Sciences of the Universe [physics]/Earth Sciences/Geochemistry
Column experiments
Water Movements
Soil Pollutants
Depleted uranium
Colloids
Groundwater
Humic Substances
0105 earth and related environmental sciences
Uranium Compounds
6. Clean water
[SDE.MCG] Environmental Sciences/Global Changes
13. Climate action
Clay
Aluminum Silicates
Adsorption
Porosity
Environmental Monitoring
DOI:
10.1016/j.scitotenv.2010.01.061
Publication Date:
2010-02-24T04:18:28Z
AUTHORS (3)
ABSTRACT
The transport of uranium through a sandy podzolic soil has been investigated in the field and in column experiments. Field monitoring, numerous years after surface contamination by depleted uranium deposits, revealed a 20 cm deep uranium migration in soil. Uranium retention in soil is controlled by the <50 microm mixed humic and clayey coatings in the first 40 cm i.e. in the E horizon. Column experiments of uranium transport under various conditions were run using isotopic spiking. After 100 pore volumes elution, 60% of the total input uranium is retained in the first 2 cm of the column. Retardation factor of uranium on E horizon material ranges from 1300 (column) to 3000 (batch). In parallel to this slow uranium migration, we experimentally observed a fast elution related to humic colloids of about 1-5% of the total-uranium input, transferred at the mean porewater velocity through the soil column. In order to understand the effect of rain events, ionic strength of the input solution was sharply changed. Humic colloids are retarded when ionic strength increases, while a major mobilization of humic colloids and colloid-borne uranium occurs as ionic strength decreases. Isotopic spiking shows that both (238)U initially present in the soil column and (233)U brought by input solution are desorbed. The mobilization process observed experimentally after a drop of ionic strength may account for a rapid uranium migration in the field after a rainfall event, and for the significant uranium concentrations found in deep soil horizons and in groundwater, 1 km downstream from the pollution source.
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