Risk assessment for groundwater resources requires most of the time the use of numerical models. These models are used to describe the migration and the transport of pollutants and to predict the contaminant evolution. the models and their parameters selection depend on the extension and the quality of the diagnosis data. the modeller has to know the limits of application of the modelling approach to improve the quality of the assessment. the research program TRANSPOL was undertaken in order to bring a better and a common practice of the use of transport models for various groups of pollutants with similar behaviour (PAH, metals, chlorine solvents . PAHs have a specific behaviour due to their strong affinity for the organic matter, their low solubility, and their density. These compounds are often associated with other contaminants and they are the major pollutants of disused coke plants, wood preservative treatment plants and ancient gas production plants. PAHs can also be found in the environment after major incidents or spills (fuels may indeed contain significant PAHs concentration). the particular behaviour of those compounds and their present and past uses justify to study the transport of the soluble and non-soluble phases. Naphthalene was especially studied with two complementary approaches. Naphthalene is used commonly as a tracer of pollution for the PAHs contamination due to its high solubility and its low capacity of adsorption, which increase its mobility.