Characterization of the benthic environment of a coastal area adjacent to an oil refinery, Todos os Santos Bay (NE-Brazil)

Abstract

In order to determine the sedimentological and physico-chemical characteristics of the benthic environment and also the level, distribution and probable sources of aliphatic and polycyclic aromatic hydrocarbons, sediment samples were collected at 28 stations in the northeast portion of Todos os Santos Bay. The centre and the east region of the study area showed characteristics of depositional environments with the predominance of silt and clay and high percentages of TOC, nitrogen and sulphur. The molar C/N ratios varied between 8.8 and 27.6 indicating a mixed origin of organic matter with variable marine and continental contributions. Total aliphatic hydrocarbon concentrations ranged between 1.56 and 246.91 µg.g-1 dry weight, corresponding the high concentrations to the stations situated in the centre and in the east region of the study area. The UCM represented between 60 and 96% of the total aliphatic hydrocarbons, indicating a high degree of anthropogenic contribution and the presence of petroleum degraded residues. Total PAH concentrations varied from 8 to 4163 ng.g-1 dry weight. The highest total PAH concentration was recorded at station 5 situated adjacent to the oil refinery.<br>Com o intuito de determinar as características sedimentológicas e físico-químicas do ambiente bentônico e também o nível, distribuição e prováveis fontes dos hidrocarbonetos alifáticos e policíclicos aromáticos, foram coletadas amostras de sedimento em 28 estações localizadas na porção nordeste da Baía de Todos os Santos. A região central e leste da área de estudo apresentaram características de ambientes deposicionais com predomínio de silte e argila e com maiores teores de carbono orgânico total, nitrogênio e enxofre. As razões C/N variaram entre 8,8 e 27,6 indicando uma origem mista da matéria orgânica com contribuições marinha e continental relativamente variáveis. As concentrações de hidrocarbonetos alifáticos totais variaram entre 1,56 e 246,91 µg.g-1 de sedimento seco, correspondendo as maiores concentrações às estações localizadas na região central e leste da área de estudo. A Mistura Complexa não Resolvida (UCM) representou entre 60 e 90% dos hidrocarbonetos alifáticos totais, indicando um alto grau de contribuição antrópica e a presença de resíduos de petróleo degradado. As concentrações de hidrocarbonetos policíclicos aromáticos totais variaram de 8 a 4163 ng.g-1 de sedimento seco. A maior concentração de hidrocarbonetos policíclicos aromáticos foi registrada na estação 5 situada na área adjacente à refinaria de petróleo

Sedimentary and Geochemical Aspects of a Refinery Impacted Coastal Area: A Case Study of the Todos os Santos Bay (Bahia, Brazil)

“…The same was found in the studies of Reference [31]. This variability in the C/N ratio is common in sheltered coastal environments with shallow depths, leading to the mixed nature of the organic matter [42].…”

“…Reference [33] observed a mean C/S ratio of 1.86 in the Santos Estuary (São Paulo State, Brazil) with a minimum of 0.09 in this estuary main channel indicating a strong reduction (anoxic) characteristic in the internal portion of the estuary where there is a larger amount of pelitic sediments and the presence of an important industrial pole. Reference [46] states that one of the sources of sulphur to marine environments is from anthropogenic nature, represented by the petroleum impact.Reference [31] also obtained, for the study area, results which indicate a high degree of anthropogenic contribution related to the residues of degraded petroleum. These authors observed still, very high contents of non-degraded petroleum (the highest of this study) in the sediments adjacent to the RLAM (stations 3, 4 and 6) which may have reflected on the high values of the C/P and N/P ratios presented by these stations in the summer of 2005.…”

“…Therefore, there are probably great quantities of organic and inorganic material in suspension in the water column which could enter the bay by means of river transport. Reference [31], while studying the distribution of organic matter in the region's sediments, observed that high contents of total organic carbon were highly correlated to total nitrogen. The same is observed in the present study with significant correlations in the winter (r 2 = 0.91), as well as in the summer (r 2 = 0.77), which indicates the presence of common sources of material.…”

Assessment of ecological quality status of Küçükçekmece Bay (Marmara Sea) by applying BENTIX, AMBI, BOPA and BO2A biotic indexes

“…Organic carbon content of sediment can be used as an indicator of pollution. Contamination concentrated at sediment will firstly and mostly affect benthic organisms that are living dependent on the sea bottom (Shine & Wallace, 2000;Venturini et al, 2004;Hyland et al, 2005). Macrofaunal communities and associated environmental variables, such as organic carbon of sediment, are important tools for detecting the health of coastal marine ecosystems (Magni, 2003).…”

Polychaete assemblage of an impacted estuary, Guanabara Bay, Rio de Janeiro, Brazil

“…The soft-bottom polychaete fauna may represent up to 70% of the total abundance and biomass in an ecosystem (GRAY, 1974), and polychaetes are extensively used as a key taxon in bioenvironmental studies to assess natural and humaninduced changes (POCKLINGTON;WELLS, 1992;JONES;KALY, 1996;PIRES, 2000;GRAY et al, 2002;FARACO;LANA, 2003;VENTURINI et al, 2004).…”