Laboratory investigation of LNAPL migration in unsaturated porous media

Abstract

Soil and groundwater contamination with non aqueous phase liquids (NAPLs) are often found at contaminated sites and it lead sophisticated procedure for remediation. This research experimentally investigates the effects of groundwater movement on the migration of LNAPL in the subsurface. Diesel was selected as LNAPL and it can be classified as a light non-aqueous phase liquid (LNAPL) because of its lower density than water. Ottawa#3820 sand and Ottawa#3 sand were used as porous media. The Simplified Image Analysis Method (SIAM) (Flores, 2010) is used as a non-intrusive and non-destructive technique to measure temporal and spatial distribution of fluid saturations in a whole domain. Linear relationships between average optical density (AOD) and degree of water saturation (S[subscript w]) and Degree of diesel saturation (S[subscript o]) for Ottawa#3820 sand and Ottawa#3821 sand were established as required by SIAM. One-dimensional column (3.5 cm x 3.5 cm x 110 cm transparent acrylics column) is used to study the effects of water table fluctuation and Two-dimensional tank (3.5 cm x 50 cm x 60 cm transparent acrylic tank) is used to study totally effects of groundwater level fluctuation and horizontal groundwater flow. 8 one-dimensional column tests and 12 two-dimensional tank tests in homogeneous and heterogeneous porous media were conducted. The results show that the water table fluctuation significantly affects the LNAPL distribution in the ground to the full range of the water saturated zone and vadose zone. A higher horizontal groundwater flow rate renders the larger diesel-contaminated area comparing with lower flow rate also results in a larger area of diesel contamination.