Hydrocarbon balance of a site which had been highly and chronically contaminated by petroleum wastes of a refinery (from 1956 to 1992)

Petroleum hydrocarbon pollution in the Gulf of Fos (South France) was studied following the cessation of petroleum waste discharge from an oil refinery in the Lavera area. Sediments were collected in core samples of 30 cm at eight stations along a radial from the refinery to the open sea. Petroleum contamination has been detected up to the beginning of the open sea but decreased gradually (from 40 to 3 g kg−1 sediment dry wt). GC profiles (aliphatics and aromatics) are characteristic of petroleum. They reveal the disappearance of short chain n-alkanes (up to C25) and of one and two aromatic ring compounds, the increase and the modification of the UCM depends on the depth and the situation, resulting from weathering processes. Biomarkers and three to five aromatic ring compounds are unaltered whatever the depth and the location. If some petroleum hydrocarbons are present for the open sea stations (perhaps from other sources), natural and pyrolytic hydrocarbons are also detected. Sediments from the open sea could be considered to be unpolluted (less than 0.1 g kg−1), and unaffected by the refinery wastes two years after the end of overspills.