ASSESSING THE FATE OF POLYNUCLEAR AROMATIC-HYDROCARBONS FROM OILY WASTE LAND SPREADING BY MODELING

The organic wastes produced by petroleum refineries are often treated by spreading them on land sites, allowing hydrocarbons to degrade natu rally. In such conditions, mathematical models representing the transp ort of organics in the soil are useful for predicting the quantities o f hydrocarbons, like polynuclear aromatic hydrocarbons (PAHs), that co uld reach the water table in the short and long term. The pesticide ro ot zone model (PRZM) simulates the fate of pesticides in the soil. Bec ause of the analogy between the agricultural use of pesticides and the land spreading of petroleum residues containing hydrocarbons, and the similar physicochemical characteristics of these two types of potenti al organic contaminants, this model was applied to a land-spreading si te in southern Quebec. The simulation results indicate that the studie d PAHs may not migrate to depths of more than 40 cm. The predicted con centrations may be several hundred times lower when the degradation ra te doubles. Natural variations in the local hydrodynamic conditions ca used by soil texture do not greatly affect the concentrations of a rel atively mobile PAH in soil or in water. In contrast to the texture, th e soil organic matter content greatly influences the distribution of P AHs between the liquid and solid phases and, consequently, their migra tion through the soil.