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Description
This research investigated how variation of hydrocarbon viscosity and soil particle size, affects the residual saturations of hydrocarbons. These residuals directly control the volume and mass of hydrocarbon that is retained by soils, which, in tum, directly influences the longevities of dissolved phase contamination resulting from such hydrocarbons. This information may directly affect the decisions of agencies attempting to remediate such contamination. Residual saturations were obtained by flooding water-wet soils with light, non-aqueous phase liquids (LNAPLs) and subsequently flushing the soils with water. Resulting hydrocarbon saturations were measured by extracting the remaining hydrocarbon from the soils using a Dean Stark apparatus. The masses of the LNAPLs extracted using this apparatus were determined with a mass balance calculation. The analysis was conducted using five test LNAPLs of varying viscosities, n-tridecane, n-dodecane, n-undecane, n-decane, and nnonane. In addition, each LNAPL was tested on five soils ranging from medium to fines. The resulting saturation distributions for the LNAPLs and soils were analyzed using basic statistical methods. Residuals produced by the above procedure suggest that for the studied range of grain sizes and hydrocarbon viscosities, that there is no correlation or effect produced by hydrocarbon viscosity on residual saturation. However, there is a strong correlation between grain size and residual saturation. Saturations in the vicinity of fifteen percent (15%) can be expected for soils with grain sizes near 0.06 mm and decreasing non-linearly to approximately three percent (3%) for soils with grain sizes in the vicinity of 0.88mm according to Srnw = -4.2 Ln (D) + 2.86 where Srnw is the non-wetting phase residual saturation and D is the grain size (diameter) in millimeters.
