# Effect of Water Content on Light Nonaqueous Phase Fluid Migration in Sandy Soil
## 1 Introduction
Using a UV spectrophotometer, [PERSON] et al. [15] simulated the migration  
Figure 1: Light nonaqueous phase fluid (LAPL) infiltration migration. process of diesel fuel in porous media under different conditions using a one-dimensional soil column experiment and analyzed the vertical migration of diesel fuel in two different grain sizes of sandy soil. [PERSON] et al. [16] simulated diesel-water two-phase flow in a porous medium with different particle sizes of glass sand in the saturated zone and obtained the saturation distribution of oil-water two-phase flow via image analysis, thus enabling quantitative analysis of saturation in multiphase flow. [PERSON] [17] combined numerical simulations with a centrifugal model test, simulating the transport process of LNAPL in unsaturated soils under homogeneous and inter-layered conditions using finite element analysis of multiphase flow in porous media. [PERSON] [18] applied multiphase flow theory to analyze the mechanisms influencing the infiltration and redistribution processes of LNAPLs in different types and structures of soils. [PERSON] et al. [19] examined the retention process of the capillary zone during the migration of LNAPL pollutants in fine sand and silt media and simulated the migration process of LNAPL under a shallow point source leakage scenario with two-dimensional sand tank experiments. [PERSON] et al. [20] built a multiphase numerical flow model based on COMSOL. They investigated the migration behavior of LNAPL in sand-filled fractured media with a combination of indoor experiments and numerical simulations. [PERSON] et al. [21] employed magnetic resonance imaging to observe the mobilization of LNAPL trapped in wet sand under natural drying conditions of a wet porous medium. [PERSON] et al. [22] estimated the volume and the distribution of LNAPLs more precisely based on the high-resolution laser-induced fluorescence technique. The migration of LNAPL in the groundwater environment is complex and involves a combination of physical, chemical, and biological processes [23]. The complexity of LNAPL migration in groundwater environmental systems is mainly manifested by the complexities of influencing factors as well as migration processes. Various factors, such as the thickness of the aquifer, characteristics of the soil in the stratum, organic matter content, depth and flow direction and velocity of groundwater, and hydrogeological conditions in which the groundwater is located, all affect the migration process, migration rate, migration volume, and the occurrence state of LNAPLs in the groundwater environment [24]. The specific issue addressed in this study is the impact of water content on the migration of light nonaqueous phase liquids (LNAPLs) in sandy soils, a critical yet under-researched aspect of subsurface contamination. To tackle this, we employed indoor simulated vertical, one-dimensional, multiphase flow soil column experiments, utilizing the orthogonal experimental method to systematically evaluate the effects of varying water contents on the occurrence state and migration rate of LNAPLs, which is important for solving environmental problems associated with LNAPL pollution in the unsaturated zone. The main research objectives of this study are as follows: (1) Analyze the effects of gravity and capillary forces on the migration rate of LNAPLs via simulations of both surface infiltration and subsurface imbibition; (2) quantitatively simulate the effects of the water content and oil content of media on the adsorption rate of LNAPL and the migration rate change process based on a one-dimensional soil column experiment. Here are the short definitions for the geological terms for the manuscript. 1. Unsaturated Zone: The unsaturated zone is the portion of the subsurface above the groundwater table where soil and rock contain both air and water in their pores. It is not a source of readily available water for human consumption but plays a crucial role in the movement of water from the land surface to the aquifer below. 2.