Concawe has recently published a report entitled "Detailed Evaluation of Natural Source Zone Depletion at a Paved Former Petrol Station”, it is available to download free of charge here.

Natural Source Zone Depletion (NSZD) encompasses all attenuation processes that result in NAPL mass loss in the subsurface. These processes include physical mass transfer by dissolution and vapourisation of chemical constituents to the aqueous (groundwater) and gaseous (soil gas) phases and biodegradation of LNAPL (Light non-aqueous phase liquid) constituents through microbially-facilitated reactions. Essentially all carbon present in LNAPL is converted to carbon dioxide and methane by biodegradation, which partition into the gas phase and migrate upward into the vadose zone. The study site is considered typical of many service stations in Europe, as a paved surface is present that extends beyond the boundaries of the site.