Analysis and storage of fluorescent dye solutions as a tracer of groundwater flow

Abstract

Fluorescent dyes are frequently used for tracing the flow of groundwater. The quantitative determination (QD) of dyes is affected by some factors during measurement and storage of the samples and that could be a cause of error in measurement. In this research, factors affect to the QD are considered and the effects of each factor are investigated. In addition, the methods to control such effects are proposed. In the measurement and pre-treatment, pH of solutions, temperature of solutions, co-existence of natural organic matter and filtration were found to affect QD significantly. However they could be controlled by buffering the pH with buffer solution, adjustment sample temperature, investigation of the fluorescent/quenching characteristics of natural organic matter and using rinsed PTFE filter, respectively. In the storage of the samples, most important point is light shielding. However sometimes dyes might be changed by microbial activity.