Impact of urban wastewater discharges on the sediments of a small Mediterranean river and associated coastal environment: assessment of estrogenic and dioxin-like activities.

The Mediterranean region includes many small coastal rivers about which little is known concerning organic contaminant loads in their sediment. This study was designed to assess organic contamination in one of these small coastal rivers (Lez River) and associated coastal sediments. Levels of alkylphenols (APs), polycylic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) were measured in sediments of the Lez River and two coastal lagoons impacted by wastewater discharges. In parallel, sediment surrounding a recently built submarine outfall that discharges treated wastewater, from an area encompassing some 450,000 inhabitants, into the sea was monitored a year after the beginning of emission via the outfall. Finally, these sediments were characterized by screening estrogenic, PAH-like and dioxin-like activities using in vitro bioassays. Both chemical analyses and bioassays revealed that wastewater inputs were a source of organic contamination of sediments from the Lez and lagoons, which still persisted 2 years after the discharges were stopped. APs could explain a small proportion of the overall estrogenic activities (up to 31%), suggesting that other estrogenic compounds were also present in the sediments. PAHs explained a great share (83% on average) of the EROD induction potency of the extracts. This survey should be the first step in the long-term monitoring of these sites.