Distribution and sources of sterol biomarkers in sediments collected from a tropical estuary in Northeast Brazil.

The Piauí-Real estuary is located along the southern coast of Sergipe state, Northeast Brazil. This estuary has great economic importance due to its physical, biological, and socioeconomic diversity, but it is subject to anthropogenic stress since the resident population in the town bordered by the estuarine system has grown in recent years. Thus, the possibility of sewage contamination originating from the approximately 450,000 inhabitants living within its drainage basin was investigated in this study. Sediment samples were collected from 15 sampling stations along the estuarine system and extracted, followed by gas chromatography-mass spectrometry (GC-MS) analysis. Six sterols were quantified, indicating natural and anthropogenic sources. Coprostanol concentrations higher than 100 ng g-1 were observed in 47 % of the stations analyzed, indicating sewage contamination, which was confirmed by the diagnostic ratios calculated. Based on the Pearson correlation test, a significant correlation between coprostanol concentrations and total organic carbon content (TOC) was observed, indicating that sterols record the history of sewage inputs in this area. These results indicate that control of the organic inputs into the estuarine system is required. Graphical abstract Sterol markers were determined and sources assessed in surface sediments from Piauí-Real estuarine system.