Laboratory and field investigation of surfactant sorption using single-well, 'push-pull' tests

Abstract

Sorption to aquifer sediments can limit the effectiveness of surfactants injected to solubilize residual nonaqueous phase liquid contaminants in the subsurface. The objective of this study was to evaluate the ability of the single-well, push-pull test to characterize sorption of linear alkylbenzene sulfonate (LAS) and hexadecyl diphenyl oxide disulfonate (DOWFAX) surfactants to natural aquifer sediment in situ. Batch sorption isotherms for both surfactants exhibited Langmuir-type sorption behavior with larger apparent sorption maxima for LAS than for DOWFAX. However, numerical transport simulations based on batch sorption isotherms were unable to predict the retardation and chromatographic separation of LAS homologs and conservative transport of DOWFAX observed during laboratory and field push-pull tests, indicating that the single-well, push-pull test method can more accurately describe in situ surfactant sorption and transport behavior than batch sorption isotherms.