Sedimentary biomarkers along a contamination gradient in a human-impacted sub-estuary in Southern Brazil: A multi-parameter approach based on spatial and seasonal variability

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The composition and seasonal variations of sedimentary organic matter were investigated along the Cotinga sub-estuary, located in Paranaguá Bay, a large South American estuary where urban activities and the primary Brazilian grain shipping port are sources of pollution. Steroids and hydrocarbons were analyzed in surface sediments collected during the austral winter (2008) and summer (2009) in three distinct sectors, along this sub-estuary in a presumed gradient of fecal contamination. Concentrations ranged from 0.28 to 7.33μgg−1 (in dry sample weight thereafter), <DL (below detection limit) to 57.2ngg−1 and <DL to 1.69μgg−1 for aliphatic hydrocarbons (ΣAHs), polycyclic aromatic hydrocarbons (ΣPAHs) and coprostanol, respectively. Petrogenic inputs may be considered as source of AHs due to the presence of unresolved complex mixture in the majority of sites; however the levels observed do not indicate oil contamination. The highest ΣPAHs concentrations were found during the summer in the middle sector of the sub-estuary but were below the threshold effect levels (TEL), suggesting the absence of contamination by PAHs. Selected PAH isomer ratios indicated pyrolytic sources, whereas fecal sterols indicated decreasing sewage contamination from sub-estuary to the open ocean. The absence of correlation between organic markers and grain-size parameters suggested no preferential deposition sites of organic matter in the study area. The Principal Components Analysis suggested spatial variation in the distribution of sterols and AHs; however, temporal variations were only evident in the distribution of PAHs.