AQUATIC HYDROCARBON DISTRIBUTIONS IN THE SEINE ESTUARY - BIOGENIC POLYAROMATICS AND N-ALKANES

Dissolved and particulate hydrocarbons of biogenic origin were investi gated for the first time in surface waters along the Seine River and i ts estuary. They comprise n-alkanes (n-ALKs) and diagenetic polycyclic aromatic hydrocarbons (PAHs). Samples were collected in three differe nt sections of the estuary: the riverine zone, the mixing zone, and th e marine zone. At the river mouth, two mooring stations were used for the collection of samples over tidal cycles. Total particulate n-ALK c oncentrations 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). T otal biogenic PAHs, accounting for 10% of the aromatic fraction, reach ed up to 76 ng l(-1), or 2 mu g g(-1) of SM. Concentrations varied wit h the SM load and could be related to sedimentation and estuarine mixi ng. The sources of the n-ALKs were different in each zone of the estua ry. The dissolved n-ALKs displayed lower concentrations than the parti culate phase, varying from 136 ng l(-1) to 344 ng l(-1), while biogeni c dissolved PAHs were almost absent.