Mobilization of NAPL as Thin Film (Sheens) at the Unsaturated Zone

Objective: The purpose of this study was to identify NAPL thin films (sheens) in soils and the mobilization of contaminants through this mechanism.

Methodology: A soil column was initially contaminated with LNAPL. After an initial survey was conducted, the water level was dropped. Repeated surveys demonstrated changes in the LNAPL distribution.

Results: Repeated surveys documented changes in the NAPL distribution, once the dropping water level turned water saturated zones into unsaturated. This change from 2-phase zones (NAPL:water) to 3-phase zones (NAPL:water:air) mobilized the NAPL in the form of thin films (sheens). Thin films move rapidly through the saturated zone, explaining the sudden appearance of NAPL sheens in surface waters that are in contact with the groundwater.

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Clear-WellJulio Zimbron