The use of environmental uranium isotopes in the study of the hydrology of the Burdekin Delta

Abstract

Analyses of bore water samples from the Burdekin Delta, Queensland, show considerable variation in both the uranium concentration and the 23l+U/238U activity ratio. In many cases, the uranium concentration was closely correlated with the bicarbonate concentration, but not for waters with a very low uranium concentration. Mechanisms by which uranium can be removed from solution are discussed. They provide a basis for explaining the low uranium concentrations and, in some areas, the apparent lack of response of the aquifer to the input of uranium by recharge. The 23I+U/238U activity ratio is interpreted as a reflection of the extent of local interaction of infiltrating ground water with soil constituents. Measurement of the isotope activity ratio has confirmed the location of an area with significant recharge from the river into the aquifer system. The isotopic and supporting chemical data illustrate the complexity of the aquifer system.