Mixing volume calculations,sources and aging trends of Floridan aquifer water by uranium isotopic methods

The activity ratio (A.R.) of two naturally occurring isotopes of uranium, U-238 and U-234, varies significantly in aqueous environments. The A.R., used in conjunction with the uranium concentration, provides a ‘fingerprint’ of groundwater masses and, by use of these parameters, mixing volumes and flow patterns can be determined. This method was applied to two large limestone springs in central Florida; the mixing volumes and flow patterns calculated are notably similar to those derived by standard hydrologic methods.In deeper parts of the aquifer, the waters are found to have low uranium concentration and a pattern of higher A.R.'s suggestive of an aging effect.