Stable carbon isotopic study (12C/13C) of the fate of petrogenic PAHs (methylphenanthrenes) during an in-situ oil spill simulation experiment

As part of a controlled simulation study, petroleum was introduced at the top of the sedimentary column in the cove of Carteau (Gulf of Fos, France). Sedimentary cores were then sampled every 6 months during 3 years. The stable carbon isotopic composition of the methylphenanthrenes was monitored throughout this oil spill simulation experiment. It has been possible to study the behavior of the petrogenic PAHs during this in-situ experiment as the isotopic composition of the petrogenic methylphenanthrenes added and the ones present in the sediment of the experimental site were significantly different. After 36 months, the methylphenanthrenes present in the contaminated core have isotopic compositions similar to the ones that were present prior to the beginning of the experiment. This result shows that the petrogenic methylphenanthrenes have been removed after 36 months while the ones that were present in the sediment before the contamination have not been affected by any of the processes responsible for the remediation of the site including water washing and biodegradation. The preferential degradation of 2-methylphenanthrene and the persistence of 9-methylphenanthrene, observed throughout this experiment, were also demonstrated using molecular stable carbon isotopic compositions.