[H-CG21] Nuclear Energy and Geoscience

[HCG21-03] Conservation of Fluorescent Dyes and the Groundwater Characteristics that Possible Decrease in its Concentration

*Ayumi Sugiyama¹, Kotaro Nakata¹, Takuma Hasegawa¹ (1.Central Research Institute of Electric Power Industry)

Keywords:fluorescent dyes, sodium fluorescein, groundwater tracers, conservative

Fluorescent dyes have been widely used as tracers in groundwater investigations and experiments. They considered to be conservative, and if their concentrations change by mechanisms other than mixing, such as adsorption or attenuation, they will have a significant impact on the results of investigations or experiments. However, when various types of groundwater and fluorescent dyes are contact with each other, the concentration of fluorescent dyes significantly decreases during storage, depending on the combination of groundwater and fluorescent dyes (Nakata et al., 2017; Sugiyama et al., submitted). In this study, the changes in concentration of fluorescent dyes over time were investigated. Three more fluorescent dyes were added to the four examined in the previous report (Sugiyama et al., submitted) and the solutions of fluorescent dyes were prepared by using 34 types of groundwater, for the experiments. Based on the results, the groundwater characteristics that affect the decrease in concentration of fluorescent dyes were discussed. If we can get some idea of the possible decrease in concentration of fluorescent dyes based on groundwater characteristics, this would be useful information when selecting fluorescent dyes for investigations and experiments.
This study was carried out under a contract with the Ministry of Economy, Trade and Industry (METI) as part of its R&D supporting program titled "Research and development on groundwater flow evaluation technology in bedrock (2022 Fy) Grant Number JPJ007597.

References
Nakata, K., Hasegawa, T. and Kashiwaya, K. (2017): Analysis and storage of fluorescent dye solutions as a tracer of groundwater flow, Journal of Groundwater Hydrology, 59(3), 205-227.
Sugiyama, A., Nakata, K. and Hasegawa, T. (submitted): Elucidation of the mechanism of fluorescent dyes concentration decrease and proposal of coping methods of its concentration decrease, Journal of Groundwater Hydrology.