PT Journal
AU Gómez, P
   Garralón, A
   Buil, B
   Turrero, MJ
   Sánchez, L
   Cruz, Bdl
TI Modeling of geochemical processes related to uranium mobilization in the groundwater of a uranium mine
SO Science of The Total Environment
PY 2006
BP 295
EP 309
VL 366
IS 1
DE Geochemical modeling; Granite; Groundwater; Uranium mine; Uranium retention
AB This paper describes the processes leading to uranium distribution in the groundwater of five boreholes near a restored uranium mine (dug in granite), and the environmental impact of restoration work in the discharge area. The groundwater uranium content varied from \textless1 μg/L in reduced water far from the area of influence of the uranium ore-containing dyke, to 104 μg/L in a borehole hydraulically connected to the mine. These values, however, fail to reflect a chemical equilibrium between the water and the pure mineral phases. A model for the mobilization of uranium in this groundwater is therefore proposed. This involves the percolation of oxidized waters through the fractured granite, leading to the oxidation of pyrite and arsenopyrite and the precipitation of iron oxyhydroxides. This in turn leads to the dissolution of the primary pitchblende and, subsequently, the release of U(VI) species to the groundwater. These U(VI) species are retained by iron hydroxides. Secondary uranium species are eventually formed as reducing conditions are re-established due to water–rock interactions.
ER