Contaminant transportContaminant transporttwo-dimensional occurs in many situations by pollutant spills which are accidentally released onto the ground surface. Factors such as the type of contaminant and soil characteristics influence how the contaminants infiltrate into the ground and spread and migrate into the groundwater, potentially affecting ecosystems and water resources. Modeling contaminant transport from a spill on the ground surface is crucial for understanding and predicting pollutants infiltrating and spreading in the subsurfaceSubsurface environment environment. In this chapter, we model the infiltration of contaminants into the ground and their spreading with the groundwater flow. Contaminant transports with different attributes of production and decay are considered.