Elucidation of the Mechanism of Fluorescent Dyes Concentration Decrease and Proposal of Coping Methods of its Concentration Decrease

Abstract

Fluorescent dyes have been commonly used as tracers to track the water movement. However, the cases of significant decrease in concentration had been observed when they were added to groundwater. In this study, we investigated changes in the concentration of fluorescent dyes when they are added to water samples and examined the mechanisms. Sodium fluorescein (uranine) and sodium naphthionate (NAP) were found to decrease significantly when they contact with groundwater, in some cases. These were suggested the microbial influence on the decrease in the concentration of these dyes. The results have shown that the micro bial activity can cause a significant decrease in the concentration of these dyes. Based on our findings, points to be considered when using fluorescent dyes as conservative tracers are summarized. Finally, we proposed an appropriate sample storage method for the analysis of fluorescent dyes concentrations.