Geochemical Markers as a Tool to Assess Sedimentary Organic Matter Sources of the Laguna Estuarine System, South Brazil: Aliphatic and Polycyclic Aromatic Hydrocarbons

Surface sediment samples from the Laguna Estuarine System were analyzed to identify organic matter sources. The ratios between selected n-alkanes, high concentrations of aliphatic hydrocarbons (AH) (average of 9,168 mu g g(-1) of organic carbon, OC) and polycyclic aromatic hydrocarbons (PAH) (total average of 426,593 ng g(-1) OC), and the hopanes distribution with alpha beta stereochemistry found in the Santo Antonio Lagoon samples were evidence that hydrocarbon inputs from petrogenic sources predominate over natural sources. In the other samples studied, the AH distribution (from 38 to 2,749 mu g g(-1) OC), and detection of hopenes and hopanes-beta beta suggest mixed sources of hydrocarbons. Nevertheless, PAH concentrations in all samples (from 7,731 to 786,469 ng g-1 OC, whereof alkyl naphthalenes accounted for > 92% of the total) indicated critical petrogenic contamination. Fishing and urban activities are potential sources to the petrogenic hydrocarbons detected in these sediment samples.