the effect of concentration and time in distribution of uranium in one calcareous soil

abstract uranium as a natural radioactive heavy metal widely disperses throughout the earth's crust. in many cases, the natural abundance has been re-distributed due to anthropogenic activities, resulting in radionuclide contamination in groundwater and surface soil. uranium through the plant uptake can enter the chain. the degree of speciation of radio nuclides in soils in areas with differing levels of uranium is of great interest in order to further the knowledge of the processes that determine the mobility and distribution of these contaminants from the installation, and consequently the potential short and long term risks. in the present work, we used a sequential extraction procedure based on tessier’s method to determine the fractionation of uranium in a calcareous soil. the effects of two levels of uranium, 585 and 3240 bq/kg 238u on the uranium distribution in soil fractions at 30 and 90 days of incubation were studied. the results indicated that u primarily associated with the carbonate fraction (62%) and increased by increasing the uranium level in soils. a comparison of extraction results from different incubation times showed that the pattern of uranium association with different fractions changed during the time of incubation.