WITHDRAWN: Effect of unsaturated flow on the occurrence and movement of light nonaqueous phase fluids

Abstract

Contamination from light nonaqueous phase fluids (LNAPL) and their derivatives during mining, production, and transportation has become a concern. Scholars have extensively studied LNAPL contamination, but the role of water content variation on its migration process in the unsaturated zone has not been sufficiently researched. In this study, indoor simulated vertical, one-dimensional, multiphase flow soil column experiments were conducted on the sandy soil of the Zhengzhou reach of the Yellow River to analyze the effect of water content on the occurrence state and migration rate of LNAPL. The experimental results indicate: (1) The migration rate of LNAPL exhibits an L-shaped trend during subsurface imbibition and a nonlinear relationship with migration time, and the migration rate and migration time of surface infiltration have a linear growth relationship. (2) The adsorption rate of LNAPL is negatively correlated with water content and positively correlated with oil content in the homogeneous non-saturated state. As LNAPL moves from the aeration zone to the saturated zone, the relationship between oil content and water content is nonlinear. (3) When the water content of the test medium is below 14% and the oil content is below 11%, LNAPL appears in the aeration zone in a solid phase. As the water content increases, the adsorption rate of the oil phase gradually decreases and eventually reaches the oil saturation point. (4) When the water content of the medium exceeds 8%, over time, LNAPL will be subject to oil-water interfacial tension, and the rate of LNAPL movement first decreases and then increases, displaying nonlinear growth.