Measurement of NAPL saturation distribution in whole domains by the Simplified Image Analysis Method

A Simplified Image Analysis Method devised to assess the saturation distribution of water and Non-Aqueous Phase Liquids (NAPLs) in granular soils subject to fluctuating groundwater conditions was developed and tested for ten different NAPLs of different density and viscosity values (0.73 ≤p ≤ 1.20 g/cm³; 1.4 ≤ v ≤ 1000 mPa.s). The Simplified Image Analysis Method, which is based on an extension of the Beer-Lambert Law of Transmittance that predicts the existence of a linear relationship between the saturation of water (S_w), NAPL (So), and their corresponding average optical densities (Di), was tested by photographing samples of Toyoura sand mixed with different amounts of water and NAPLs, using two digital cameras with different wavelength band-pass filters (λ = 450 nm and 640 nm), and obtaining the linear equations relating S_w, S_o and D_i for the each NAPL. Once the linear relationships were confirmed, this method was used to assess the behavior of two different NAPLs subject to fluctuating groundwater tables, demonstrating that this non-intrusive and non-destructive method can be used as a reliable tool to provide water and NAPL saturation distributions in full domains, when studying the effects of porous soil contamination by NAPLs under dynamic conditions.