Experimental Investigation of Three-Dimensional Diffusion Behavoiur of Crude Oil Types in Soil Environment

Crude oil contamination continues to pose a major environmental threat in the Niger Delta due to persistent spills, equipment failure, pipeline corrosion, and operational negligence. Understanding the diffusion behaviour of different crude oil types in soil is critical for predicting subsurface migration, assessing ecological risk, and designing effective remediation systems. This research presents an experimental study on the three-dimensional diffusion behaviour of light, medium, and heavy crude oils in loamy soil obtained from Ahaoda West, Rivers State, Nigeria. Experimental diffusion studies were carried out under controlled conditions to measure the temporal and spatial migration of the three crude types along depth (longitudinal direction) and lateral flow paths (left and right). Results showed that diffusion rate increased with time for all crude oil types. Light crude exhibited the fastest diffusion rate due to lower viscosity, followed by medium crude, while heavy crude demonstrated the slowest spread and highest near-surface retention. Vertical (longitudinal) diffusion was significantly greater than lateral diffusion for all crude types, confirming that gravitational effects and soil–oil interaction control the dominant direction of migration in loamy soil. A consistent trend emerged: light crude recorded the highest diffusion coefficients in both directions, while heavy crude showed the lowest values. The findings contribute new scientific insights and practical tools that can support environmental monitoring, risk assessment, and remediation decision-making in the Niger Delta and other oilproducing regions.