Abstract This research study sought to evaluate aimed at evaluating the possible advantages of using Fuzzy Logic as opposed to Boolean Logic to assess environmental contamination and source appraisal for polycyclic aromatic hydrocarbons (PAH). Results obtained through traditional assessment tools for two different tropical coastal areas through using traditional clustering and principal components analysis were compared with those derived from the Fuzzy Logic, using the by Fuzzy C-means algorithm. The feedings achieved through Fuzzy Logic showed a greater qualitative detail than those derived from traditional tools. The abrupt and unnatural changes obtained from the usual classification methods were avoided by having membership values varying continuously in space, providing a more accurate picture of environmental contamination in complex and multiple sources environments. Furthermore, by not depending on statistic suppositions distribution of data like other methods, becomes more suitable for environmental data. Although Fuzzy Logic does not produce quantitative interpretations, its application generates adequate the data needed to avoid environmental management bias in the inference of contamination sources.

Marcadores moleculares na classe de lipídios (esterois, ácidos graxos e hidrocarbonetos) e a composição isotópica (δ13C e δ15N) da matéria orgânica bruta foram quantificados em amostras de um testemunho de sedimento para caracterizar o histórico recente de sedimentação da matéria orgânica na plataforma continental adjacente à Baía de Guanabara, no Estado do Rio de Janeiro. Na superfície do sedimento (0-1 cm), a concentração total de esterois e ácidos graxos foi cerca de uma ordem de grandeza maior do que observado nas camadas mais profundas do sedimento, com predominância de lipídios derivados da produção planctônica. Esses resultados sugerem, como confirmado através de estatística multi-variada, a ocorrência de um evento de elevada produção primária na coluna d'água e uma exportação rápida e eficiente das partículas para o sedimento. Condições similares são observadas na região de ressurgência de Cabo Frio, localizada cerca de 150 km ao norte da área de estudo. Portanto, nossos resultados sugerem que tais eventos têm uma influência regional sobre a produção primária na margem continental sudeste do Brasil. Por outro lado, a presença de lipídios derivados de plantas vasculares de origem continental ressalta a necessidade de investigar com maior profundidade a influência relativa entre forçantes físicas e o aporte continental sobre processos biogeoquímicos na porção da plataforma continental considerada no presente trabalho.

Sterol and fatty acid biomarkers and isotopic composition (δ13C and δ15N) of bulk organic matter (OM) were quantified in a sediment core to characterize the accumulation of autochthonous OM in an area on the continental shelf adjacent to Rio de Janeiro State. In the sediment surface (0-1 cm) the concentration of total sterols and fatty acids was at least one order of magnitude higher than that measured deeper down in the core and was dominated by labile and planktonic-derived biomarker compounds. These results suggest, as is confirmed by multivariate statistical analysis, the occurrence of an event of enhanced primary production in the water column and efficient export of particles to the bottom. Similar conditions have been observed at Cabo Frio, located 150 km to the north of our study site, during an upwelling event, suggesting that such events may exert a regional influence on primary production on the south-eastern Brazilian continental shelf. Beyond the signatures from this event, the presence of biomarker compounds from vascular plants suggests the additional influence of an outflow from Guanabara Bay at the study site. These results point to the need for further investigation of the relative influence of physical forcings and continental inputs on the biogeochemical processes on the section of the continental shelf considered in the present study.

The history of sewage contamination in the Mundaú-Manguaba estuarine lagoon system (NE Brazilian coastal zone) was evaluated through the concentration of sterols in sediment cores. The concentration of coprostanol increased towards the surface sediments, with the maximum of 5.65 µg g-1 at 0-2 cm sediment layer in Mundaú. Manguaba exhibited a lower level of contamination. The ratio cholestanol/cholesterol suggested degradation of coprostanol only before the burial of organic matter in the sediment. This feature, together with information of population growth in the watershed, allowed the estimation of a sedimentation rate of 0.90 cm year-1 to the Mundaú lagoon.

As enseadas de Icaraí e Jurujuba, localizadas na porção sudoeste da Baía de Guanabara, são sujeitas a impactos ambientais decorrentes da ocupação humana nas suas bacias de drenagem. No presente trabalho foi determinada a composição elementar (C e N) e molecular (esteróides) da matéria orgânica em amostras de sedimentos superficiais (n = 24) e de um testemunho curto (c = 47 cm) nas enseadas. As concentrações de coprostanol, em comparação com outras áreas da Baía de Guanabara, indicaram elevado nível de contaminação por esgotos nas estações mais próximas ao ponto de lançamento de efluentes, na Enseada de Icaraí. A Enseada de Jurujuba, mais enclausurada e eutrófica, apresentou uma maior contribuição de matéria orgânica autóctone, conforme evidenciado pelos marcadores colesterol, dinosterol, e parcialmente, também , brassicasterol. A presença de estigmasterol e b-sitosterol indicaram leve contribuição de matéria orgânica oriunda de vegetação terrestre, conforme revelou a análise por componentes principais. No registro sedimentar, foram observados maiores teores de matéria orgânica e esteróis na camada superior, corroborando a acumulação recente de esgotos e de matéria orgânica fitoplanctônica, como conseqüência do processo de eutrofização do sistema. A presença de processos de degradação da matéria orgânica foi evidenciada pelas razões entre esteróis/estanóis, e o perfil do dinosterol indicou que na Enseada predomina o acúmulo de material fitoplanctônico anteriormente ao processo de eutrofização.

The interconnected Icaraí and Jurujuba embayments, set within the lower south-eastern portion of Guanabara Bay, SE-Brazil, have been subject to the direct input of domestic effluents and other associated contaminants from human activities in their watersheds. This study addresses the composition of carbon, nitrogen and molecular steroid markers of surface sediments (n = 24) and a short core (L = 47 cm), in order to evaluate the impact by sewage, the contribution between allochthonous and autochthonous derived organic matter and eutrophication of the embayments. Coprostanol concentrations revealed, when compared to other regions in Guanabara Bay, high contamination by sewage close to the point of sewage discharge in Icaraí embayment. In contrast, the more enclosed and eutrophic Jurujuba embayment exhibited a larger contribution of autochthonous organic matter, as shown by the combination of cholesterol, dinosterol and, partially, also brassicasterol. The presence of stigmasterol and b-sitosterol also indicated a minor contribution of organic matter from terrestrial plants, as revealed by principal component analysis. The sedimentary record of the Jurujuba embayment exhibited highest concentrations of all sterol markers in the top layer, corroborating the recent increase in the accumulation of sewage, plankton derived organic carbon and also eutrophication. Trend in degradation of organic matter was evidenced by sterol/stanol ratios and the behavior of dinosterol indicated that the embayment has been dominated by the accumulation of phytoplankton derived organic matter since earlier times.