ORGANIC COMPOUNDS AS PROXIES OF THE SEDIMENTARY ENVIRONMENTAL QUALITY OF THE MARICÁ-GUARAPINA LAGOON SYSTEM (SE, BRAZIL)

Bottom sediment is a natural trap for organic matter and different kinds of pollutants. The accumulation of large amount of organic matter gives rise to the eutrophication of the aquatic ecosystems. The analyses of the quantity and quality of the organic matter (biopolymers) help to determine the trophic status of coastal ecosystems. The Maricá-Guarapina Lagoon System (MGLS) is located in Rio de Janeiro and is composed by four connected lagoons: Maricá, Barra, Padre and Guarapina. It has been suffering impacts due to the intense and uncontrolled property speculation. Based on this problem, this study aimed to characterize the organic matter (OM) amount and quality in sediments and the relation with the impacted areas in this lagoon system. The collected sediment samples were analyzed for geochemical data combined with grain size and physical-chemical environmental parameters of the bottom water. Statistical results evidenced that the sedimentary environment of the MGLS is heterogenous. The organic matter supplied to the MGLS is provided from different sources but the autochthonous contribution (phytoplanktonic productivity and vegetal detritus from the mangrove fringe) prevails. The anthropogenic contribution was more evident in Padre Lagoon, where the sediments had relatively low TOC contents (0.1-0.8%). The MGLS is accumulating mainly aged organic matter. The most impacted zones were found in Guarapina, Barra and Maricá lagoons, in bottoms of fine-grained sediments, with relatively high TOC and labile biopolymeric compounds (proteins, carbohydrates and lipids) contents, which should evolve into an ever-increasing stage of eutrophication. COMPOSTOS ORGÂNICOS USADOS COMO INDICADORES DA QUALIDADE AMBIENTAL SEDIMENTAR DO SISTEMA LAGUNAR MARICÁ-GUARAPINA (SE DO BRASIL)ResumoO sedimento de fundo constitui uma armadilha natural para a matéria orgânica e diferentes tipos de poluentes. O acúmulo de grande quantidade de matéria orgânica dá origem à eutrofização dos ecossistemas aquáticos. Estimativas de quantidade e qualidade da matéria orgânica (biopolímeros) podem ajudar a determinar o estado trófico dos ecossistemas costeiros. O Sistema Lagunar de Maricá-Guarapina (MGLS), localizado no Estado do Rio de Janeiro (SE do Brasil), é composto por quatro lagunas interconectadas: Maricá, Barra, Padre e Guarapina. Este sistema tem sofrido impactos devido à intensa e descontrolada especulação imobiliária. Neste contexto, este estudo teve como objetivo caracterizar a quantidade e qualidade de matéria orgânica (MO) dos sedimentos do MGLS. Foram obtidos dados geoquímicos e confrontados com resultados granulométricos em amostras de sedimentos coletados em 22 estações de amostragem e analisados parâmetros físico-químicos da água. Os resultados estatísticos evidenciaram que o ambiente sedimentar do MGLS é heterogêneo. Este sistema recebe matéria orgânica de diferentes fontes, sendo, porém, prevalecente a contribuição autóctone (produtividade fitoplanctônica e detritos vegetais dos manguezais existentes na região). A contribuição antropogênica de matéria orgânica foi mais evidente na Lagoa do Padre, onde os sedimentos apresentaram teores de COT relativamente baixos (0,1-0,8%). As zonas mais impactadas foram encontradas em fundos de sedimentos finos, com teores relativamente elevados de COT e de compostos biopoliméricos lábeis (proteínas, carboidratos e lipídios), nas lagunas de Guarapina, Barra e Maricá. Os resultados obtidos revelam também que o MGLS está acumulando principalmente matéria orgânica envelhecida e permitem prever que as referidas áreas podem evoluir para um estágio de cada vez maior grau de eutrofização.Palavras-chave: Lagunas Costeiras Tropicais. Biopolímeros. Eutrofização. Dinâmica Sedimentar.

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IMPACT OF EUTROPHICATION ON BENTHIC FORAMINIFERA IN SEPETIBA BAY (RIO DE JANEIRO STATE, SE BRAZIL)

Journal of Sedimentary Environments ◽

10.12957/jse.2019.47327 ◽

2019 ◽

Vol 4 (4) ◽

pp. 480-500 ◽

Cited By ~ 3

Author(s):

Maria Virgínia Alves Martins ◽

Egberto Pereira ◽

Rubens Cesar Lopes Figueira ◽

Thales Oliveira ◽

Anita Fernandes Souza Pinto Simon ◽

...

Keyword(s):

Organic Matter ◽

Rio De Janeiro ◽

Chemical Elements ◽

Sepetiba Bay ◽

Fine Grained ◽

210Pb And 137Cs ◽

Se Brazil ◽

Radiocarbon Data ◽

Abundance And Diversity ◽

The Impact

The main objective of this work is to analyze the consequences of eutrophication in benthic meiofaunal organisms (foraminifera) in an internal area of Sepetiba Bay (State of Rio de Janeiro, SE, Brazil). This study is interesting because, at the studied site, the sediments corresponding to the period of greatest accumulation of organic matter were not contaminated by metals, although Sepetiba Bay has areas known to be polluted by this type of contaminants. Thus, in this study, it was possible to consider only the impact caused by eutrophication.In the SP6 core, collected in the Sepetiba Bay internal area and studied in this work, textural, geochemical (concentration of chemical elements; 210Pb and 137Cs; radiocarbon data) and foraminifera were analyzed in a muddy section, with a few intercalations of sandy layers. The sediments of the analyzed section were deposited in the last ≈2,350 BP years. The concentrations of Al, Cd, Co, Fe, Mn, Ni, Pb, Sn, Ti, V and Zn are higher at the base of the core and decrease towards the top. The contents of TOC, P and Zr have inverse paterns. The ratios of these elements to their background value have similar patterns. However, previous studies have recognized that during the twentieth century Cd, Zn, Cr and Pb concentrations increased in several areas of Sepetiba Bay, mainly due to industrial activity. The area where this core was collected may have been dredged. Radiocarbon ages suggest a loss of ≈2000 years of sedimentary registration, marked by an unconformity at a depth of 126 cm, probably caused by dredging. A new sedimentary sequence unpolluted by metals but highly enriched in organic matter was deposited on the surface of that discontinuity. Foraminifera were quite abundants in the lower section (240-126 cm; between ≈2,400-2,090 years BP, execept in the sandy layers), corresponding to sediment deposition before dredging. After dredging, the accumulation of very fine-grained sediments rich in organic matter generated eutrophication phenomena, which caused a drastic reduction in the abundance and diversity of these organisms. This work testifies the effect of eutrophication on meiofaunal organisms. Although some coastal foraminifer species tolerate harmful effects caused by eutrophication, it is recognized that the impact has been so negative that even these species occur with reduced abundance in the study area. IMPACTO DA EUTROFICAÇÃO EM FORAMINIFEROS BÊNTONICOS NA BAÍA DE SEPETIBA (ESTADO DO RIO DE JANEIRO, SE BRASIL) ResumoO principal objetivo deste trabalho é analisar as conseqüências da eutrofização em organismos meiofaunais bentônicos (foraminíferos) em uma área interna da Baía de Sepetiba (Estado do Rio de Janeiro, SE, Brasil). Este estudo é interessante porque, no local estudado, os sedimentos correspondentes ao período de maior acumulação de matéria orgânica, não estavam contaminados por metais, apesar da Baía de Sepetiba ter áreas reconhecidamente poluídas por este tipo de contaminantes. Assim neste estudo foi possível considerar apenas o impacto causado pela eutrofização.No testemunho SP6, coletado na área interna da Baía de Sepetiba e estudado neste trabalho, foram analisados dados texturais, geoquímicos (concentração de elementos químicos; 210Pb e 137Cs; dados de radiocarbono) e foraminíferos numa secção lamosa, com intercalações de camadas arenosas.Os sedimentos da seção analisada foram depositados nos últimos 2.350 anos BP. As concentrações de Al, Cd, Co, Fe, Mn, Ni, Pb, Sn, Ti, V e Zn são mais elevadas na base do testemunho e diminuem em direção ao topo. O conteúdo de TOC, P e Zr possui padrões inversos. As razões destes elementos com o respectivo valor de fundo possuem padrões semelhantes. Porém, estudos anteriores reconheceram em várias áreas da Baía de Sepetiba um aumento das concentrações de Cd, Zn, Cr e Pb durante o século XX, principalmente devido à atividade industrial. A área onde foi coletado este testemunho poderá ter sido dragada. As idades de radiocarbono sugerem uma perda de aproximadamente 2000 anos de registro sedimentar, marcada por uma inconformidade a 126 cm de profundidade, causada provavelmente por dragagem. Uma nova sequência sedimentar não poluída por metais, mas bastante enriquecida em matéria orgânica foi depositada sobre a superfície da descontinuidade. Os foraminíferos eram relativamente abundantes na seção inferior (240-126 cm; entre ≈2.400-2.090 anos BP), correspondente á deposição de sedimentos antes da dragagem. Após a dragagem, a acumulação de sedimentos muito finos e ricos em matéria orgânica, gerou fenómenos de eutrofização, que terão causado uma redução drástica da abundância e diversidade destes organismos. Este trabalho testemunha o efeito da eutrofização em organismos meiofaunais. Apesar de algumas espécies de foraminíferos costeiros tolerarem efeitos nefastos causados pela eutrofização, reconhece-se que o impacto foi tão negativo que mesmo estas espécies ocorrem com abundância reduzida na área estudada. Palavras-chave: Área Costeira. Registro Paleoambiental. Impacto Antrópico. Meiofauna, Abordagem Multiproxy.

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Impact of treated sewage on meiobenthic nematodes: a case study from the Tunisian Refining Industries Company

Brazilian Journal of Biology ◽

10.1590/1519-6984.246116 ◽

2022 ◽

Vol 82 ◽

Author(s):

A. Hedfi ◽

M. Ben Ali ◽

A. Noureldeen ◽

H. Darwish ◽

T. Saif ◽

...

Keyword(s):

Organic Matter ◽

Environmental Parameters ◽

The Other ◽

Treated Sewage ◽

Before And After ◽

Bizerte Bay ◽

De Man ◽

The Impact

Abstract The main objective of the current study was to assess the impact of the water taken from the ‘Tunisian Refining Industries Company’ on meiobenthic nematodes, before and after a series of treatments in decantation basins followed by its discharge in Bizerte bay, Tunisia. The comparison of environmental parameters of the two types of water was clearly indicative of an improvement in the quality of treated waters after a significant reduction in their loads in hydrocarbons. Overall, the water retained a good quality after being treated by ‘Tunisian Refining Industries Company’ before discharge in the sea. At the end of the experiment, differential responses were observed according to the richness of sediment in organic matter and hydrocarbons. Thus, it was apparent that the nematode assemblage exposed to the treated waters was closer to controls and associated to higher values of abundance, than that under untreated ones. It was also assumed that the species Microlaimus honestus De Man, 1922, Paramonohystera proteus Wieser, 1956 and Cyartonema germanicum Juario, 1972 are sensitive bioindicators of bad environmental statues and of hydrocarbon presence in the environment. On the other hand, Metoncholaimus pristiurus (Zur Strassen, 1894) Filipjev, 1918 would rather be classified as a positive bioindicative species of this type of pollutants.

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ANALYSIS OF THE WATER QUALITY INDEX OF THE NEGRO AND RESENDE RIVERS IN DUAS BARRAS DISTRICT, RIO DE JANEIRO (BRAZIL) / ANÁLISE DO ÍNDICE DE QUALIDADE DAS ÁGUAS DOS RIOS NEGRO E RESENDE NO DISTRITO SEDE DE DUAS BARRAS, RIO DE JANEIRO (BRASIL)

Journal of Sedimentary Environments ◽

10.12957/jse.2018.35715 ◽

2018 ◽

Vol 3 (2) ◽

pp. 121-130

Author(s):

Isabella Robert Rodrigues ◽

Mauro César Geraldes ◽

Andréa Alves Ferreira ◽

Marcelo Dos Santos Salomão ◽

Sérgio Vieira Anversa

Keyword(s):

Water Quality ◽

Water Quality Index ◽

Rio De Janeiro ◽

Quality Index ◽

Potential Temperature ◽

Oxygen Demand ◽

Water Bodies ◽

Se Brazil ◽

Thermotolerant Coliforms

In Brazil, about 49% of the population does not have access to the sewage collection network, with the consequent direct discharge of their sewage network into water bodies. Due to this scenario, it is essential to investigate the quality of the water consumed by thousands of people along the Negro and Resende Rivers. The present study analysis the waters of the Negro and Resende rivers, located in Dois Rios River Basin, in the municipality of Duas Barras, Rio de Janeiro State (RJ, SE Brazil), based on the Water Quality Index proposed by the National Sanitation Foundation (United States). The population of the district located in the municipality of Duas Barras dumps the domestic sewage directly into the hydrographic network. The analyzed parameters were: turbidity, total solid residue, total phosphorus, total nitrogen, biochemical oxygen demand (BOD), hydrogenation potential, temperature, dissolved oxygen and thermotolerant coliforms. The values obtained from the calculation of the Water Quality Index (WQI) showed a variation from 40 to 68, meaning that the quality of water vary between bad and acceptable in the study area. The samples collected in the urban area contained values for thermotolerant coliforms in disagreement with the maximum value permissible for classes 2 and 3 of fresh water by CONAMA (Conselho Nacional do Meio Ambiente; a Brazilian Council for the Environment) Resolution 357/2005. The results of the analyzes confirmed the contamination of the two rivers by the discharge of domestic effluents, showing that actions are necessary to eliminate or minimize the discharge of sewage in the surveyed water bodies, since it may cause public health risks. ResumoNo Brasil, cerca de 49% da população não possui acesso à rede de coleta de esgoto, com o consequente despejo direto da sua rede de esgotos em corpos hídricos. Diante deste cenário, torna-se indispensável investigar a qualidade da água consumida por milhares de pessoas ao longo dos rios Negro e Resende. A presente pesquisa analisou qualitativamente as águas dos rios Negro e Resende, localizados na Bacia Hidrográfica do Rio Dois Rios, no município de Duas Barras/RJ, a partir do índice de qualidade das águas proposto pela National Sanitation Foundation. A população do distrito sede do município de Duas Barras despeja o esgoto doméstico diretamente na referida rede hidrográfica. Os parâmetros analisados foram: turbidez, resíduo sólido total, fósforo total, nitrogênio total, demanda bioquímica de oxigênio, potencial hidrogêniônico, temperatura, oxigênio dissolvido e coliformes termotolerantes. Os valores obtidos no cálculo do índice de qualidade das águas (IQA) mostraram uma variação de 40 a 68, significando uma qualidade da água entre ruim e razoável. As amostras coletadas na área urbana apresentaram valores para coliformes termotolerantes em desacordo com o valor máximo permitido para classes 2 e 3 de água doce, regulamentados pela Resolução CONAMA 357/2005. O resultado das análises confirmou a contaminação dos dois rios pelo lançamento de efluentes domésticos, os quais poderão originar riscos de saúde pública. Os resultado evidenciam a necessidade de se desenvolverem ações para eliminar ou minimizar os despejos de esgotos nos referidos corpos hídricos.

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Analysis of Sedimentary Environment Conditions for Lacustrine Fine-Grained Sedimentary Rocks and Its Control of Lithofacies Development: A Case Study of the Lower Submember of Member 3 of Shahejie Formation in FY-1 Well, Dongying Sag, Bohai Bay Basin, China

Geofluids ◽

10.1155/2021/6640706 ◽

2021 ◽

Vol 2021 ◽

pp. 1-16

Author(s):

Jun Peng ◽

Ledan Yu ◽

Tianyu Xu ◽

Yubin Wang ◽

Haodong Han

Keyword(s):

Saline Water ◽

Sedimentary Environment ◽

Geochemical Data ◽

Bohai Bay ◽

Bohai Bay Basin ◽

Fine Grained ◽

Dongying Sag ◽

Shahejie Formation ◽

Three Stages ◽

The Relationship

In recent years, the studies on fine-grained sedimentation mainly focus on the rock type, sedimentary environment, sedimentation, and sequence stratigraphy, while those on the relationship between sedimentary environment and lithofacies development are rare. However, a clear understanding on the relationship is of great significance to the muddy shale oil and gas exploration. This paper studied the muddy shale of semideep and deep lacustrine facies in the lower submember of Member 3 of Shahejie Formation in FY-1 Well, Dongying Sag, Bohai Bay Basin, East China. Based on geochemical data, the sedimentary environment media conditions and vertical changes of this submember were analyzed by means of core description, thin section authentication, X-ray diffraction (XRD), and other technologies, and the relationship between sedimentary environment and lithofacies development was discussed. The results show that this environment underwent three stages and is featured by cyclicity. From the bottom up, it experienced the semideep, deep, and deep/semideep waters under the relatively dry-cold/relatively warm-wet, warm-wet, and warm-wet/relatively warm-wet paleoclimates, respectively. Correspondingly, the paleoredox transited three stages from reducibility to high reducibility to high reducibility/reducibility; the paleosalinity changed from saline water to brackish water to brackish/saline water. Paleoproductivity was low/relatively high at the beginning, then became high, and finally relatively high. In this submember, the lithofacies primarily includes organic-rich mudstone, organic-rich lime mudstone, organic-rich lime-bearing mudstone, and organic-contained argillaceous limestone/lime mudstone. The sedimentary environment controls the mineral composition and content in the lithofacies and thus determines the lithofacies types. Meanwhile, the cyclicity of environmental change not only leads to that of the lithofacies development but also affects the positions of the lithofacies and its assemblages in sequence stratigraphic framework.

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Lithofacies and Sedimentation of Organic Matter in Fine Grained Rocks of Nanggulan Formation in Kulon Progo, Yogyakarta

Journal of Applied Geology ◽

10.22146/jag.26964 ◽

2016 ◽

Vol 1 (2) ◽

pp. 82

Author(s):

Donatus Hendra Amijaya ◽

Najibatul Adibah ◽

Ahmad Z.A. Ansory

Keyword(s):

Organic Matter ◽

Depositional Environment ◽

Inorganic Material ◽

Middle Eocene ◽

Late Eocene ◽

Geochemical Data ◽

Environment Analysis ◽

Shallow Marine ◽

Fine Grained ◽

Gas Source

Fine grained rocks especially shale play a significant role in shale hydrocarbon system. Research on Eocene Nanggulan shale becomes an interest lately since this shale is considered as prospective interval for shale gas source. It potentially contains significant organic matter because coaly sediment is found in this formation as well. Nanggulan Formation fine grained rocks was deposited in various depositional environment from estuary – shallow marine. This paper integrates the result of lithofacies and depositional environment analysis with organic geochemical data to understand the sedimentation process of organic matter. Samples were taken from cores. The result of 14 geochemically analysed samples shows Total Organic Carbon (TOC) content between 0.36–1.00 % for fin e grained rocks (shales) and 12.80 % for coaly shales. Nine samples are categorized as fair and 2 samples are categorized as good source rock. The depositional environment of Nanggulan Formation sediment, which was shallow marine at Late Eocene and estuary (salt marsh) at Early Eocene, produced sediment with higher TOC. Whereas the deposition of sediment in estuary (tidal flat) at Middle Eocene produced lower content of TOC. Vulcanic activity at Middle Eocene also caused less organic material preservation because it produced abundant inorganic material.

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ORGANIC POLLUTION IN THE NE SECTOR OF GUANABARA BAY (SE, BRAZIL) / POLUIÇÃO ORGÂNICA NO SETOR NE DA BAÍA DE GUANABARA (SE, BRASIL)

Journal of Sedimentary Environments ◽

10.12957/jse.2018.37826 ◽

2018 ◽

Vol 3 (3) ◽

pp. 138-154 ◽

Cited By ~ 3

Author(s):

Maria Virginia Alves Martins ◽

René Rodrigues ◽

Egberto Pereira ◽

Paulo Miranda ◽

Lazaro Laut ◽

...

Keyword(s):

Organic Matter ◽

Organic Pollution ◽

Oil Refinery ◽

Hydrocarbon Generation ◽

Guanabara Bay ◽

Fine Grained ◽

Se Brazil ◽

Maturation Index ◽

Geochemical Analyses ◽

Rock Eval

This study characterizes the quantity and quality of organic matter present in surface sediments of the NE sector of Guanabara Bay (SE, Brazil), based on geochemical and statistical analysis. The geochemical analyses included stable isotopes in sedimentary bulk organic matter (orgδ13C), total organic carbon (TOC), total sulfur (TS) and Rock Eval pyrolysis parameters, such as free hydrocarbons (S1), generating source potential (S2), production index (PI), oxygen and hydrogen indices (OI, HI) and the maturation index of organic matter (Tmax). The analyzed data were statistically treated to ﬁnd main factors that are influencing the sedimentary composition. The low activity of the bottom currents favors the deposition of fine-grained sediments, rich in organic matter, in most of the studied area. The organic matter present in the sediments is being supplied by local and allochthonous sources and can be considered a good source of type III kerogen, and therefore has the potential to generate gas, if the geological context is adequate. Considering the quantity, type of organic matter and potential of hydrocarbon generation four main groups of stations were identified. Stations in which the sediments: i) encompass a relatively high component of OM sourced mainly from the adjacent continental areas close to the Apa de Guapimirim (less contaminated by oil) and S. Gonçalo (Roncador River) regions; ii) contain some autochthonous contribution, located between the Paquetá and Governador Islands, where biogenic gas seeping should be predicted hereafter; iii) have higher contamination by oil, situated near Mauá and REDUC Oil Refinery, of Duque de Caxias; iv) present intermediate characteristics, located in the remaining study area. ResumoEste estudo efetua a caracterização da quantidade e qualidade da matéria orgânica presente em sedimentos superficiais do setor NE da Baía de Guanabara (SE, Brasil), com base em análises geoquímicas e estatísticas. Os dados geoquímicos incluíram isótopos estáveis em matéria orgânica (ORGδ13C), carbono orgânico total (TOC), enxofre total (TS) e parâmetros de pirólise Rock Eval, como por exemplo, teores se hidrocarbonetos livres (S1), potencial de geração hidrocarbonetos (S2), índice de produção (PI), índices de oxigênio e hidrogênio (OI, HI) e índice de maturação da matéria orgânica (Tmax). Os dados analisados foram tratados estatisticamente a fim de serem identificados os principais fatores que influenciam a composição sedimentar. A fraca atividade das correntes de fundo, favorece a deposição de sedimentos finos ricos em matéria orgânica, na maior parte da área estudada. A matéria orgânica presente nos sedimentos está sendo fornecida por fontes locais e alóctones e pode ser considerada uma boa a excelente fonte de querogênio do tipo III, tendo, pois, potencial para a geração de gás, desde que o contexto geológico seja adequado. Considerando-se a quantidade, o tipo de matéria orgânica e o potencial de geração de hidrocarbonetos podem ser identificados quatro grupos principais de estações. Estações em que os sedimentos: i) possuem teores relativamente elevados de matéria orgânica oriunda principalmente das áreas continentais, localizadas próximo da Apa de Guapimirim (menos contaminadas por petróleo) e S. Gonçalo (Rio Roncador); ii) contêm alguma contribuição autóctone, situadas entre a Ilha de Paquetá e a Ilha do Governador, onde se poderá prever a ocorrência de libertação de gás biogênico num futuro próximo; iii) possuem maior contaminação por petróleo, localizadas próximo de Mauá e da refinaria Reduc, de Duque de Caxias; iv) apresentam características intermédias, situadas na restante área de estudo.

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EVALUATION OF THE ENVIRONMENTAL STATE OF THE WESTERN SECTOR OF SEPETIBA BAY (SE BRAZIL): TRACE METAL CONTAMINATION

Journal of Sedimentary Environments ◽

10.12957/jse.2019.43764 ◽

2019 ◽

Vol 4 (2) ◽

pp. 174-188 ◽

Cited By ~ 5

Author(s):

Shéron Joyce Díaz Morales ◽

Josefa Varela Guerra ◽

Márcia Andréia Da Silva Nunes ◽

Ariadne Marra de Souza ◽

Mauro César Geraldes

Keyword(s):

Trace Metals ◽

Rio De Janeiro ◽

Water System ◽

Bottom Surface ◽

Icp Oes ◽

Sepetiba Bay ◽

Western Sector ◽

Se Brazil ◽

Local Water

Sepetiba Bay located in Rio de Janeiro State (RJ), Southeast Brazil, is a region under heavy influence of seaports and mining. This feature puts at risk the quality of the local water system, especially due to the deposition of trace metals on the sediments. This work aimed to report the values of total concentrations of Ag, As, Cd, Co, Cr, Cu, Li, Mn, Ni, Pb, Sr, Zn and Hg obtained in bottom surface sediments collected in Nov/2010 in the Western sector of Sepetiba Bay, through the Plasma Spectrometer (ICP-OES). The average concentrations of Ag (0.40 µg/g), Cd (0.76 µg/g), Cu (62.59 µg/g), Li (43.29 µg/g), Ni (16.65 µg/g), Pb (20.08 µg/g), Sr (389.64 µg/g) and Zn (184.2 µg/g) exceeded the limits allowed by Brazilian legislation, and are, in addition, above the natural values found in Ribeira Bay (RJ), the considered control region. It is necessary to monitor this area, due to its economic and environmental importance. AVALIAÇÃO DO ESTADO AMBIENTAL DO SETOR OCIDENTAL DA BAÍA DE SEPETIBA (SE BRASIL): CONTAMINAÇÃO POR METAIS TRACEResumoA Baía de Sepetiba localizada no Estado do Rio de Janeiro (RJ), sudeste do Brasil, é uma região sob forte influência de portos marítimos e mineração. Esta característica coloca em risco a qualidade do sistema de água local, especialmente devido à deposição de metais traço nos sedimentos. Este trabalho tem como objetivo reportar os valores das concentrações totais de Ag, As, Cd, Co, Cr, Cu, Hg, Li, Mn, Ni, Pb, Sr, U e Zn obtidos em sedimentos de superfície de fundo coletados em Nov / 2010 no Setor Oeste da Baía de Sepetiba, através do Espectrômetro de Plasma (ICP-OES). As concentrações médias de Ag (0,40 µg / g), Cd (0,76 µg / g), Cu (62,59 µg / g), Li (43,29 µg / g), Ni (16,65 µg / g), Pb (20,08 µg / g ), Sr (389,64 µg / g) e Zn (184,2 µg / g) ultrapassaram os limites permitidos pela legislação brasileira, e estão, além disso, acima dos valores naturais encontrados na Baía da Ribeira (RJ), a região de controle considerada. É necessário monitorar esta área, devido à sua importância econômica e ambiental. Palavras-chave: Total Trace Metals. Sedimentos Litoral. Contaminação

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Organic petrology, geochemistry, and hydrocarbon generation capacity of Permo–Carboniferous source rocks in the Mahu Sag, northwestern Junggar Basin, China

Energy Exploration & Exploitation ◽

10.1177/01445987211023856 ◽

2021 ◽

pp. 014459872110238

Author(s):

Zhijun Qin ◽

Dongming Zhi ◽

Kelai Xi

Keyword(s):

Organic Matter ◽

Higher Plants ◽

Sedimentary Environment ◽

Junggar Basin ◽

The Other ◽

Source Rocks ◽

Western China ◽

Geochemical Data ◽

Lower Permian ◽

Hydrocarbon Generation

The Mahu Sag in the Junggar Basin, China, is a hydrocarbon-rich sag. Abundant hydrocarbon source rocks were developed in the late Paleozoic there across the Carboniferous–Permian boundary. However, studies of the source rocks have focused mainly on the lower Permian Fengcheng Formation. Here we compare the Fengcheng Formation with other Carboniferous rocks and those of the lower Permian Jiamuhe and middle Permian Lower-Wuerhe formations. Based on organic petrological and geochemical data, the organic matter precursors, sedimentary facies, and resource potential of these source rocks were investigated. The bio-precursors of Carboniferous, Jiamuhe, and Lower-Wuerhe Formations were dominantly estuarine higher plants, Nematothallus -higher plants, and spores, respectively. The bio-precursors of Fengcheng Formation were mainly bacteria and algae, and the organic matter is abundant, with a high hydrocarbon-generating capacity and significant shale oil potential. In contrast, the other three formations contain poor-quality source rocks, although the Lower-Wuerhe Formation has a higher organic matter abundance than the Jiamuhe Formation. The Carboniferous organic matter contains mainly type II kerogen, whereas the Jiamuhe and Lower-Wuerhe formations contain type III kerogen. The thermal maturities determined from Tmax values is larger than those indicated by biomarkers. The biomarkers show that the three studied formations contain a mixture of terrestrial higher plants and bacteria–algae, with the contribution of green algae being higher than that of bacteria in most samples. However, the ratio of algae to bacteria is lower than that of the Fengcheng Formation. The Fengcheng Formation was deposited in a strongly reducing, high-salinity, and water-stratified sedimentary environment. The other three formations were deposited in an oxidizing–reducing, low-salinity, and water-unstratified environment. They are characterized by the predominance of mudstone over carbonate rocks and the descending distribution type of tricyclic terpenes. Our results provide a basis for research on upper Paleozoic source rocks in western China, and useful information for oil and gas exploration in the Mahu Sag.

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