Investigation of Fluorescent Dyes as Partitioning Tracers for Subsurface Nonaqueous Phase Liquid (NAPL) Characterization

Five fluorescent dyes were evaluated as partitioning tracers for detection and quantification of tetrachloroethylene (PCE): fluorescein, rhodamine A WT (RWT), sulforhodamine B (SRB), eosine, and pyranine. Results obtained from batch tests were (a) sorption partitioning coefficients (KP) 0.088+-0.025 and 0.091 cm^3/g, for RWT and SRB, respectively (eosine and pyranine increased fluorescence after soil/dye batch tests; thus, KP could not be obtained for these tracers) and (b) nonaqueous phase liquid/water partitioning coefficients (KNW) for RWT, SRB, and eosine were 0.1703, 0.0603, and 0.049, respectively (pyranine also increased fluorescence in PCE/dye tests). Retardation factors (Rf) measured in column tests for fluorescein, RWT, SRB, eosine, and pyranine were (a) 1.08+-0.07, 1.64+-0.38, 1.23, 1.45, and 2.97, in the absence of PCE; and (b) 1.31, 2.3, 1.33, 1.79, and 3.51, in the presence of PCE, respectively. The results of this study suggested that the partitioning behavior of the tracers tested is different from simple hydrophobic partitioning and that their fluorescence is complex and dependent upon several variables. Column tests indicated that RWT, SRB, and eosine are possibly suitable as partitioning tracers.