A detailed and predictive understanding of actinide ion transport by groundwater through geological strata has yet to be achieved. New experimental techniques are needed to detect both the oxidation state and the chemical behavior of these ions at very low concentrations. Laser techniques based on the optical properties of actinide ions are evaluated as probes for identification of the oxidation state of a specific ion. A laser-induced fluorescence study of aquo curium 3+ ion is reported. This technique is extremely sensitive but of limited applicability to actinide ions in solution. Thermal lensing spectroscopy, applicable to all actinide ion oxidation states in solution, is being developed. Preliminary results indicate that actinide ion concentrations between 2 and 100 μmol/m3 can be detected in aqueous solution using thermal lensing. The exact detection limit depends on the actinide ion, its oxidation state, and the spectral region used for the investigation. A means of overcoming the sensitivity limitation imposed by the optical absorbance of water itself is discussed.