Fate and Transport Modeling of PFOS in a Fractured Chalk Aquifer Towards a Large Scale Drinking Water Abstraction

Background/Objectives. In December 2005 the largest explosion in Western Europe since World War Two occurred at the Buncefield Oil Storage Terminal in the UK. In controlling the resulting fires approximately 250,000 litres of firefighting foam containing PFOS were deployed, a proportion of which directly impacted the underlying chalk Principal Aquifer which lies within a protected drinking water abstraction zone. Investigations identified PFOS to be present in groundwater beneath the site resting at approximately 35m below ground level, source concentrations of PFOS ranged from between 20 to 50µg/l well above the 0.3 µg/l guidance values in the UK.

Many questions remain regarding the fate, transport, attenuation, and remediation of PFOS, which is classed as a persistent organic pollutant (POP). Recent advancements in the science of environmental toxicology of PFAS have drawn attention to these chemicals and the need for a better understanding of their behaviour in the environment.

Results/Lessons Learned. The project has resulted in significant insights being gained regarding transport of PFOS in fractured rock at the site, including characterization of background PFOS concentrations and attenuation mechanisms such as retardation and dual-porosity mass transfer characteristics. Giving the significant increase in recognition of the number of potential PFAS source zones globally and the significant number of drinking water supplies at risk these insights will be of interest to a wide audience.