Molecular and stable carbon isotopic source identification of oil residues and oiled bird feathers sampled along the Atlantic coast of France after the Erika oil spill

The Erika tanker broke in two close to the Atlantic coast of France on December 12, 1999. On December 25th, some heavy fuel oil released by the tanker came ashore along the French Atlantic Coast. Some oil residues and oiled bird feathers were collected all along the Atlantic Shoreline of France after the wreck of the Erika tanker. The aim of this study was to differentiate oil residues and oiled bird feathers related to the Erika oil spill from the ones resulting from the numerous tar ball incidents which had accurred after the Erika oil spill. Alkane and PAH quantification of oil residues allowed differentiation of the samples collected on the north part of the Atlantic Coast from those collected on the south part of the Atlantic shoreline. All oiled birds appear to have been contaminated by the Erika oil. Samples collected on the south part of the Atlantic Coast contain a different molecular fingerprint compared to the Erika oil indicating that they are not related to the Erika oil spill. Bulk and molecular (13)C/(12)C ratio measurements were performed in order to check the discriminative feature and the stability of the isotopic approach. Bulk stable carbon isotopic composition has been shown to be a valuable screening correlation tool as it confirms the link of samples collected in the north part of the Atlantic Coast with the Erika oil spill. All the samples collected along the south part of the Atlantic Shoreline exhibit (13)C-enriched bulk isotopic compositions compared to Erika oil. Molecular isotopic composition of saturated hydrocarbons and of phenanthrene compounds also allows unambiguous differentiation of samples related to the Erika oil spill from those due to tar ball incidents. Over the long-term, when molecular distribution will have been modified by the different processes affecting oil in the marine environment, molecular isotopic composition should then be of particular help for Erika oil residues identification.