Aquatic hydrocarbon distributions in the Seine estuary: Biogenic polyaromatics and n-alkanes

Dissolved and particulate hydrocarbons of biogenic origin were investigated for the first time in surface waters along the Seine River and its estuary. They comprise n-alkanes (n-ALKs) and diagenetic polycyclic aromatic hydrocarbons (PAHs). Samples were collected in three different sections of the estuary: the riverine zone, the mixing zone, and the marine zone. At the river mouth, two mooring stations were used for the collection of samples over tidal cycles. Total particulate n-ALK concentrations ranged from 31 ng l(-1) to 2,918 ng l(-1), or 5 mu g g(-1) dry weight to 101 mu g g(-1) dry weight of suspended matter (SM). Total biogenic PAHs, accounting for 10% of the aromatic fraction, reached up to 76 ng l(-1), or 2 mu g g(-1) of SM. Concentrations varied with the SM load and could be related to sedimentation and estuarine mixing. The sources of the n-ALKs were different in each zone of the estuary. The dissolved n-ALKs displayed lower concentrations than the particulate phase, varying from 136 ng l(-1) to 344 ng l(-1), while biogenic dissolved PAHs were almost absent.