Sewage contamination in a tropical coastal area (São Sebastião Channel, SP, Brazil)

• Urban sewage contamination was studied in São Sebastião Channel.
• Only sites near the main sewage outfall showed significant contamination levels.
• Hydrodynamic and sedimentary processes trigger spatial distribution of sewage.

Urban effluent discharges in Brazilian coastal areas are a chronic problem and often lead to changes in the quality of the marine environment. São-Sebastião-Channel (SSC) is an important aquatic ecosystem to be monitored for urban sewage contamination due to the intense urban activities in that region, as well as the relative high biodiversity of marine organisms. In the area are present three submarine sewage outfalls, a commercial harbour and also the biggest oil terminal in Brazil. Total organic carbon (TOC), total nitrogen (TN), total sulphur (TS), steroids and linear alkylbenzenes (LABs) were measured in sediment samples collected in three strategic locations of the SSC in order to monitor urban sewage contamination. Total LAB and total sterols levels ranged from below DL–51.3 ng g−1 and below DL–10.40 μg g−1, respectively. Samples collected near sewage outfall in the central part of the SSC had higher concentrations of urban sewage-associated contaminants.