Modelling the Fate of Petroleum Hydrocarbons in Groundwater

Models can be powerful tools to aid interpretation of data and for prediction of the fate of contaminants, as in the case of petroleum hydrocarbons in groundwater environments. Here we describe the transport processes that can be more or less dominant at different stages in the ‘life’ of a petroleum contaminant spill in groundwater, such as advection, dispersion, dissolution from free-phase non-aqueous phase liquid (NAPL), sorption to aquifer material, and biodegradation processes. Consideration of all of these processes may be warranted to provide a comprehensive assessment of the natural attenuation of hydrocarbon compounds in groundwater or for remediation strategy design. Adequate data and a sound conceptual model of plume development and hydrogeochemical response are prerequisites for more comprehensive and realistic modelling. Knowledge of aquifer properties, geochemistry, suitable boundaries of the domain to be studied and indeed the intent of the modelling – all shape the conceptual model and the level of effort required. Some of the available biogeochemical numerical codes are catalogued, and one is applied in an example problem as a demonstration of model capabilities. The example concerns the natural attenuation (biodegradation) of a dissolved petroleum hydrocarbon plume in groundwater, accounting for coupling of transport, geochemistry, NAPL dissolution and microbial growth and decay.