Organic and inorganic contamination in sediments from Araçá Bay, São Sebastião, Brazil

The aim of this work is to verify the organic and inorganic contamination in Araçá Bay, which contains one of the last remnants of mangrove forest on the northern coast of São Paulo State, Brazil, to improve the environmental management of this area, which is part of the Marine Protected Area of the Northern Coast of São Paulo State (APAMLN) and the Environmental Protected Area of the Alcatrazes Municipality (APAMA). Surface sediments were analyzed to provide information on the levels, spatial trends and sources of trace elements, aliphatic hydrocarbons (AH), polycyclic aromatic hydrocarbons (PAH), and fecal steroids. Low levels of trace elements were observed, and the enrichment factors showed no evidence of contamination in the area. The highest concentrations of all organic contaminants were recorded in the samples collected in the external sublittoral stations, mainly in the São Sebastião Channel, which had the finest grain sizes and higher OC contents. With the exception of the samples collected in the inner part of the bay, most of the samples presented unresolved complex mixtures (UCM) of AH, which are indicators of petroleum and its derivative inputs. PAH concentrations were higher in the external stations, but the levels were below the limits of the sediment quality guidelines (SQG) recommended in Brazilian federal legislation on dredged sediments. The major sources of these compounds were from pyrolytic sources. Sewage contamination was detected mainly in the inner part of the bay, especially near the northern stream and the sewage outfall. The contaminant distributions were related to the hydrodynamics of the intertidal flat, with the most central dynamic areas presenting lower contaminant levels.