Evaluation of sediment contamination by polycyclic aromatic hydrocarbons in the Gironde estuary

Surface sediments, collected in the Gironde estuary during February and October 1993, were analysed for polycyclic aromatic hydrocarbons (PAHs). The aromatic fractions were separated by liquid chromatography of the extracts and analysed by gas chromatography/mass spectrometry (GC/MS). Total PAH concentrations ranged among 1000 to 2000 ng/g of dry sediment. The resulting distributions and molecular ratios of specific aromatic compounds (phenanthrene, anthracene, fluoranthene, pyrene…) have been discussed in terms of sample location, origin of the organic matter and seasonal variations. The collected data show that this estuary is moderately contaminated. The level of contamination and the relative distributions of PAHs are quite homogeneous throughout the estuary. A strong pyrolytic source fingerprint has been recorded, but the detection of high amounts of perylene, which is always the most abundant PAH, indicates a dominant biogenic origin for the organic matter. Slight seasonal variations in composition have also been observed.