Amostras de sedimentos superficiais do Sistema Estuarino de Laguna foram analisadas objetivando a identificação das fontes de matéria orgânica. Razões entre n-alcanos selecionados, elevados teores de hidrocarbonetos alifáticos (HA) (média de 9.168 µg g -1 de carbono orgânico, CO) e policíclicos aromáticos (HPA) (média total de 426.593 ng g -1 CO), e a distribuição de hopanos com estereoquímica αβ detectados nas amostras da Lagoa de Santo Antônio foram evidências de que o aporte de hidrocarbonetos petrogênicos prevalece sobre os de fontes naturais. Nas demais amostras estudadas, a distribuição de HA (de 38 até 2.749 µg g -1 CO), a detecção de hopenos e hopanos-ββ sugerem hidrocarbonetos de fontes mistas. Todavia, o teor de HPA em todas as amostras (de 7.731 até 786.469 ng g -1 CO, sendo que os aromáticos alquilados representaram > 92% do total) revelou contaminação petrogênica crítica. As atividades pesqueira e urbana são fontes potenciais dos hidrocarbonetos petrogênicos detectados nas amostras sedimentares.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 µg 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 αβ stereochemistry found in the Santo Antônio 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 µg g -1 OC), and detection of hopenes and hopanes-ββ 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.
Keywords: hydrocarbons, hopanes, PAH, sediment, chromatography
IntroductionEstuaries are important areas of world's coastal zones. In general, they are highly productive and provide spawning and nursery grounds for migratory species, besides playing a significant role in the global carbon cycle.1,2 Furthermore, an overwhelming majority of the human populations is concentrated along or near coasts, which inevitably leads to complex problems concerning environmental quality due to the residues generated by miscellaneous human activities.Along with various other organic and inorganic contaminants, the study of sedimentary aliphatic hydrocarbons (AH) (e.g., n-alkanes and hopanes) provides an important tool to assess organic matter sources and pollution levels in aquatic ecosystems. [3][4][5] This class of organic compounds has biogenic and anthropogenic sources. Natural inputs are comprised mostly of vascular plants, algae, microorganisms and early diagenesis of natural products, whereas petroleum and its derivatives are generally examples of hu...
