In order to understand the practicability of RATU, the amount of Hg2+ in tap water and pool water were determined by our proposed fluorescence assay method, and the results were listed in Table 1. The data revealed a good agreement between the added and the found concentrations of Hg2+. The recovery was between 98.0% and 102.3%. The relative standard deviation (RSD) of three measurements was less than 1.8%. Thus, the present method could be effectively determined Hg2+ in real water samples.