Evaluation of anthropogenic contamination using sterol markers in a tropical estuarine system of northeast Brazil.

The São Francisco River estuarine system, located in the Northeast coast of Brazil, has great economic, tourist and social importance. Its waters are used for activities such as agriculture, aquaculture, navigation and fishery, which supplies the surrounding communities. In this study, sterols markers were determined in twenty-eight sediment samples from São Francisco River estuary by gas chromatography - mass spectrometry (GC-MS). Sterol analysis was useful to distinguish between anthropogenic and biogenic organic matter (OM) sources in the studied area. Six sterols were quantified, suggesting different sources. Concentrations of fecal sterol (coprostanol) were lower than 500ngg(-1), suggesting no indicative of severe sewage contamination.However, two stations showed concentrations around 100ngg(-1) and the values for the coprostanol/(coprostanol+cholestanol) and coprostanol/cholesterol ratios indicates sewage contamination. The results in this study may be considered as baseline concentrations to be used as future reference for monitoring programs to prevent anthropogenic impacts.