Influence of a solubility‐enhancing agent (cyclodextrin) on NAPL‐water partition coefficients, with implications for partitioning tracer tests

[1] The partitioning tracer test (PTT) is used to quantify subsurface nonaqueous phase liquid (NAPL) saturations (SN). The laboratory-measured NAPL-water partitioning coefficient (KNW) is required to calculate the SN. The complexing agent hydroxypropyl−β−cyclodextrin (HPCD) has been used to successfully remediate NAPL-contaminated sites. Residual concentrations of HPCD may remain in the groundwater during a postremediation PTT. This investigation examines the influence of HPCD on the trichlorethene NAPL-water partitioning coefficients of several alcohol tracers. Laboratory results indicate that aqueous HPCD concentrations of 2000 mg/L result in the reduction of KNW values by up to 33%. This effect can result in up to 33% error in the PTT-estimated SN. The effect decreases as the original KNW value of a tracer decreases. The relationship between KNW values and HPCD concentrations is nonlinear and yields curves characteristic of each tracer. Empirical relationships are offered to reproduce the characteristic curves based on tracer KNW values to allow estimates of corrected KNW values for an arbitrary tracer.