Cassia O. Farias

Hydrocarbons in sediments of a chronically contaminated bay: the challenge of source assignment.

Aliphatic hydrocarbons and 39 PAH (parental and alkylated homologs) determined in ca. 100 sediment samples from the Guanabara Bay, Rio de Janeiro, were evaluated for source discrimination using new approaches. Concentrations of total PAH were in the range of 96-135,000 μg kg(-1) similar to other coastal urbanized embayment. Traditional diagnostic ratios were not as efficient PAH source indicators, e.g. biomass combustion was assigned as the major source of the pyrolytic PAH although the hydrographic basin is highly industrialized and urbanized. It is proved petrogenic imprint cannot be detected if only the 16 USEPA PAH are determined. The high production in the eutrophic system is not apparent in the aliphatic fraction dominated by land derived n-alkanes due to the effectiveness of microbial degradation. The present work demonstrates the complexity of hydrocarbon forensics when applied to chronically contaminated environments.

Trace metal contamination in mangrove sediments, Guanabara Bay, Rio de Janeiro, Brazil

The Guanabara Bay in Rio de Janeiro has undergone profound alterations of its natural environmental conditions. Metal concentration increase in sediments has been reported to be among these alterations. Trace-metal contamination and availability were studied in sediments of 3 mangrove areas of the bay. Cd, Zn, Pb, Ni, Cu and Al concentrations were determined in segments of sediment cores, after treatment with 1 mol L-1 HCl and with concentrated HNO3. Fe and Mn were determined in the leach with HNO3. Concentrations were low in comparison to those reported for Guanabara Bay and Cd showed up to 90% recovery in the HCl extract. Sediments found to be oxic to suboxic showed AVS concentrations in range of 0.07 (bottom) to 18.79 mmol g-1(sub-surface) indicating heterogeneity and apparent disequilibrium. Fe and Mn oxides, carbonates and organic matter may be the most important phases controlling metal availability and distribution.

Hidrocarbonetos e esterois como indicadores de fontes e destino de matéria orgânica em sedimentos da Baía de Sepetiba, Rio de Janeiro

The inputs of organic matter derived from natural and anthropogenic sources to Sepetiba Bay were investigated by using aliphatic hydrocarbons and sterols in superficial sediments. Concentrations ranged from 0.26 to 2.65 μg g-1, <0.01 to 17.41 μg g-1 and 0.77 and 9.24 μg g-1 for n-alkanes, UCM (unresolved complex mixture) and total sterols, respectively. The selected markers and ratios among individual compounds showed the major contribution of terrestrial sources to the total pool of sedimentary organic matter in the bay, but the accumulation of autochthonous organic matter increased with distance from the shoreline. The input of petroleum hydrocarbons and sewage (coprostanol in the range 0.01 to 0.43 μg g-1) were also detected, especially in the more urbanized regions of the bay, but at lower levels of contamination when compared to estuaries in other Brazilian coastal regions.

Urban rivers as conveyors of hydrocarbons to sediments of estuarine areas: source characterization, flow rates and mass accumulation.

Aliphatic (n-C12-n-C40, unresolved complex mixture, resolved peaks) and aromatic hydrocarbons (46 PAH) were investigated in suspended particulate matter (SPM) sampled over eleven months in six of the major rivers and two channels of the Guanabara Bay Basin. PAH flow rates of the most contaminated rivers, the contribution to the PAH sediment load of the receiving bay, and the main sources of hydrocarbons were determined. PAH (38) ranged from 28 ng L(-1) to 11,514 ng L(-1). Hydrocarbon typology and statistical evaluation demonstrated contribution of distinct sources in different regions and allowed quantification of these contributions. Total flow rate for the five major rivers amounts to 3 t year(-1) and responds for 30% of the total PAH annual input into the northern area of the Guanabara Bay. For the first time PAH mass deposited in the bay sediments has been estimated and shall serve as base for decision making and source abatement.

Hydrocarbon composition and distribution in a coastal region under influence of oil production in northeast Brazil

Waters and sediments from the Potiguar Basin (NE Brazilian coast) were investigated for the presence and nature of polycyclic aromatic hydrocarbons (PAH) and aliphatic hydrocarbons. The region receives treated produced waters through a submarine outfall system serving the industrial district. The total dispersed/dissolved concentrations in the water column ranged from 10-50 ng L(-1) for ∑16PAH and 5-10 μg L(-1) for total aliphatic hydrocarbons. In the sediments, hydrocarbon concentrations were low (0.5-10 ng g(-1)for ∑16PAH and 0.01-5.0 μg g(-1) for total aliphatic hydrocarbons) and were consistent with the low organic carbon content of the local sandy sediments. These data indicate little and/or absence of anthropogenic influence on hydrocarbon distribution in water and sediment. Therefore, the measured values may be taken as background values for the region and can be used as future reference following new developments of the petroleum industry in the Potiguar Basin.

8 – ORIGEM E DISTRIBUIÇÃO DA MATÉRIA ORGÂNICA SEDIMENTAR USANDO INDICADORES GEOQUÍMICOS*

RESUMO Lipidios biomarcadores [acidos graxos (FA), esterois e alcoois], isotopos estaveis (δ13C e δ15N), aminoacidos totais hidrolisaveis (THAA) e carbono orgânico total (COT) foram quantificados em 215 amostras de sedimentos superficiais coletadas em dois periodos (seco e chuvoso de 2008/2009) entre 25 e 3.000 m de profundidade ao longo de nove transectos transversais a margem continental. Tambem foram analisadas amostras de sedimento superficial em dois cânions (Grussai e Almirante Câmara) para os mesmos indicadores, com excecao de isotopos. O objetivo foi investigar os processos relacionados com a origem, transporte e acumulo de materia orgânica (MO) na regiao de estudo. Nas amostras dos transectos, a composicao de lipidios biomarcadores sugeriu a predominância de materia orgânica derivada de produtores primarios e secundarios na coluna d’agua, mas foram observados gradientes espaciais significativos da qualidade e quantidade da materia orgânica sedimentar. As menores concentracoes de lipidios, com predominância de compostos labeis, foram medidas na plataforma continental (< 150 m), exceto nas areas influenciadas por ressurgencia costeira e/ou por intrusao subsuperficial de aguas mais ricas em nutrientes, onde maiores concentracoes de carbono orgânico total e lipidios foram obtidas. O talude superior e medio (400 a 1.300 m) tambem exibiram elevadas concentracoes de carbono orgânico total e lipidios, mas com uma maior influencia de lipidios ja alterados pela atividade bacteriana. Isto sugeriu que ha exportacao de materiais de areas rasas para o talude, possivelmente devido a acao de vortices e meandros da Corrente do Brasil e por correntes de fundo. No talude inferior (1.900 a 3.000 m), apenas os compostos mais recalcitrantes foram medidos acima dos limites de deteccao. Em relacao aos cânions, a distribuicao dos lipidios biomarcadores sugeriram que eles sao locais efetivos de acumulo e transporte de materia orgânica labil para porcoes mais profundas da margem continental. No geral, os isotopos e os aminoacidos totais hidrolisaveis proveram informacoes que foram consistentes e corroboraram as observacoes feitas com base nos lipidios biomarcadores.

Reconstructing historical changes in combustion patterns by means of black carbon and pah evaluation in dated sediments from Guanabara Bay, Rio de Janeiro

The accumulation history of combustion products from the metropolitan area around Guanabara Bay was evaluated using black carbon and polycyclic aromatic hydrocarbons as indicators. BC concentration varied between 0.23 and 0.51%, with an increasing mass accumulation tendency over the last 118 years, whereas a decrease in the values of the ratio BC/organic carbon was observed in the upper sediment layers, probably reflecting the enhancement of bays eutrophication process in the last 30 years. Higher concentrations of pyrolytic PAH were observed between 1925 and 1976, being consistent with the subsequent deforestation, urbanization, and industrialization that occurred in the Guanabara basin in the period. These PAHs were best characterized by the BFl/(BFl+BePy) diagnostic ratio. The data obtained allowed the characterization of the main events that influenced the combustion patterns in the region: burning of biomass and fossil fuel, economic crisis of 1970 and 1990 and the introduction of ethanol in the Brazilian energetic matrix.

Historical evolution of organic matter accumulation in a coastal bay in the SW Atlantic, Brazil: use of sterols and n-alcohols as molecular markers

The deposition processes and preservation of organic matter (OM) in the sediments of Ilha Grande Bay, SW Atlantic, were evaluated based on elemental composition (C and N) and molecular markers (sterols and n-alcohols). Samples from four dated sediment cores, representing distinct levels and type of human influence, were analyzed. The concentration of total sterols ranged from 71 to 9,320 ng g-1, with 24-ethyl-cholesta-5,22-dien-3β-ol, 24-ethyl-cholesta-5-en-3β-ol and 24-ethyl-5a-cholesta-3β-ol as the most abundant compounds. The n-alcohols, with a total concentration between 130 and 15,407 ng g-1, were dominated by long-chain compounds (> C22). Assignments of the selected markers to terrestrial or marine sources were evaluated using principal component analysis (PCA). The trends and events that influenced the OM accumulation in the last decades were also revealed by the PCA, as the increasing human settlement in the region and the removal of a mangrove forest occurred between 1940 and 1960. The absence or low level of sewage contamination was indicated by the sterol coprostanol and associated indexes.

10 – HIDROCARBONETOS EM SEDIMENTOS DA BACIA DE CAMPOS*

RESUMO O objetivo do presente estudo constituiu-se da avaliacao e caracterizacao dos hidrocarbonetos e de carbono negro (BC) presentes em sedimentos da Bacia de Campos. Para tal foram coletadas amostras superficiais em 108 estacoes distribuidas de Cabo Frio ao Cabo de Sao Tome, entre as isobatas de 25 e 3.000 m, em duas estacoes do ano. Foram estudados, tambem, sedimentos dos cânions Grussai e Almirante Câmara. Encontraram-se, em geral, baixas concentracoes de hidrocarbonetos policiclicos aromaticos (HPAs), para os quais as razoes diagnosticas indicaram origem pirogenica ou mista (pirogenica e petrogenica). No entanto, em todas as amostras determinou-se a serie de hopanos e esteranos maturados, que e indicativa da presenca de oleo, e apenas em algumas amostras, na fracao alifatica, ha mistura complexa nao resolvida e serie homologa completa de n-alcanos. A contribuicao de carbono negro para o conjunto de carbono orgânico (Corg) foi muito elevada, demonstrando o dominio de carbono orgânico recalcitrante nos sedimentos e o significativo aporte de material originado de queima incompleta de materia orgânica. Houve correlacoes estatisticas entre carbono negro e os hidrocarbonetos policiclicos aromaticos de 5-6 aneis principalmente provenientes de processos de combustao incompleta. Identificou-se o talude como regiao de deposicao, onde ocorrem as concentracoes mais elevadas de todos os compostos estudados.

7 – AVALIAÇÃO DE CONTAMINANTES ORGÂNICOS EM ÁGUAS SUPERFICIAIS DA BACIA DE CAMPOS*

RESUMO Hidrocarbonetos policiclicos e alifaticos foram determinados em amostras de agua do mar superficial coletadas na area da Bacia de Campos compreendida entre o Cabo de Sao Tome e Cabo Frio e as isobatas de 25 e 3.000 m (oito isobatas e nove perfis perpendiculares a costa), totalizando 72 estacoes de coleta visitadas em dois periodos aqui denominados chuvoso e seco. As amostras para determinacao de hidrocarbonetos foram extraidas segundo o metodo EPA 3510. Os hidrocarbonetos alifaticos, hidrocarbonetos totais de petroleo (HTP), hidrocarbonetos policiclicos aromaticos (HPAs), fenois e benzeno, tolueno, etilbenzeno e xilenos (BTEX) foram determinados segundo os metodos EPA 8015B, EPA 8270C e EPA 502.2, respectivamente. As concentracoes de todos os compostos mostraram-se baixas nas duas campanhas de amostragem. Fenois e BTEX mostraram-se abaixo do limite de quantificacao do metodo. Porem, no periodo seco, foi observada a presenca de n-alcanos e de mistura complexa nao resolvida (MCNR) com caracteristicas de origem petrogenica degradada ou nao.