This paper analyses the behavior of a Light Non-Aqueous Phase Liquid (LNAPL) in a porous subsurface when subjected to a fluctuating water table, by using an image analysis method to calculate LNAPL and water saturation distribution values for a three-phase (air-watercontaminant) column test. It was shown that the image analysis method described here can be used as an economic and efficient tool to study the behavior of LNAPLs (such as petroleum sub-products and others) when released in sandy soils.
Soils and groundwater contaminations with heavy metals, chlorinated organic compounds, hydrocarbons, and other toxic chemicals are major geoenvironmental issues. These contaminants can be either soluble or insoluble in water. Soluble contaminants, such as salts, dissolve in groundwater and travel with it as a mixture with water. In contrast, due to their low solubility, some other contaminants such as chlorinated organic compounds and hydrocarbons behave as an independent liquid phase from water. These insoluble liquid phase, also called Non- Aqueous Phase Liquids (NPALs), form a physical interface with water that prevents them from mixing. When NAPLs are released into the subsurface via a spill or leak, they tend to migrate downward through the vadose zone. The fate, flow and transport of NAPLs are governed by complex interactions among capillary, viscous and gravity forces, mass transfer between phases and chemical and biological reactions. These processes are also affected by factors such as temperature, soil and fluid compressibility, soil heterogeneity, volume of spilled NAPL and geometry of the spill source (Kamon et al., 2007). In general, if a large enough amount of a NAPL is released into the subsurface, lighter-than-water insoluble contaminants, or Light NAPLs (LNAPLs), such as hydrocarbons, will float on top of the aquifers and usually spread over them as free lenses whereas heavier-than-water insoluble contaminants, or Dense NAPLs (DNAPLs), such as chlorinated solvents, will tend to sink to the bottom of the same aquifers following the slopes of the confining layers.
