18 research outputs found

    Distribution of lipid compounds in sediments from Conceição Lagoon, Santa Catarina Island, Brazil

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    Lipid compounds from five sediment-water interface samples and a sediment core with 75 cm depth were used to assess sources of organic matter in Conceição Lagoon, located on Santa Catarina Island. The results which were based on the molar C:N:P ratios, relative abundance of sterols (dominated by the C27 sterols), n-alkanols (0.2-1.2 µg g-1), n-alkanes (0.4-5.0 µg g-1) and the Carbon Preference Index (CPI), indicated that the organic matter is predominantly of terrestrial origin (C/N > 10 and CPI > 2). Total phosphorus (TP, average 5.20 µmol g-1) and organic carbon (TOC, average 2.90 mmol g-1) contents were well correlated with the silt and clay fractions at all locations. In the sediment core, chronologically dated with the radionuclide 210Pb, the depth interval from 55 to 75 cm was dominated by the sand fraction (> 50%). However, parameters such as TOC, TP and n-alkane contents increased considerably at this depth suggesting a change in organic matter input sources

    Distribution and sources of aliphatic and polycyclic aromatic hydrocarbons in surface sediments of Itajaí-Açu estuarine system in Brazil

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    The Itajaí-Açu estuarine system, located in southern Brazil, has great economic importance due to the presence of two ports (Itajaí and Navegantes). This system is affected by industrial and dredging activities, which can cause the remobilization of pollutants accumulated over time in the sediment. In this context, hydrocarbons were assessed in twelve surface sediment samples. n-Alkane and polycyclic aromatic hydrocarbons (PAH) concentrations were determined by gas chromatography and their sources assessed. Total concentrations ranged between 0.50 ± 0.04 and 69.70 ± 3.90 μg g-1 dry weight (d.w.) for n-alkanes and from 63.9 ± 12.1 to 1459.0 ± 43.5 ng g-1 d.w. for PAH. Most of the sediment samples presented carbon preference index (CPI) values close to unity, indicating that the area is submitted to petroleum-related sources, mainly close to Itajaí harbor, where an intense unresolved complex mixture (UCM) was observed. The presence at all stations of αβ-hopane biomarkers also indicated petrogenic input. Based on selected PAH ratios, the sedimentary PAH composition reflects a mixture of both petrogenic and pyrolytic sources. A comparison of the PAH concentrations found in this study with those listed in the sediment quality guidelines (SQGs) indicated that adverse biological effects on the biota are rarely expected.The Itajaí-Açu estuarine system, located in southern Brazil, has great economic importance due to the presence of two ports (Itajaí and Navegantes). This system is affected by industrial and dredging activities, which can cause the remobilization of pollu28460361

    Lipids as indicators of paleoclimatic changes, II: terrestrial biomarkers

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    Variations in the abundance of specific lipid biomarker compounds derived from terrestrial sources are shown to be closely related to past climatic changes. Despite biodegradation processes, which take place mostly at the water column and sediment water interface, these compounds are found well preserved in oceanic sediments. Here, their relative distribution is employed as a tool to assess changes in terrestrial fluxes to the seabed accompanying climatic variations during glacial and interglacial intervals. These changes in biomarker distribution were estimated in two sediment cores taken ttom the eastern North Atlantic, covering the past 210,000 years. Comparisons with other paleoclimate proxies showed good agreement and suggest that some specific groups of biomarkers are important indicators of changes in terrestrial inputs to the sea.<br>A variação na abundância de alguns biomarcadores lipídicos derivados de aportes terrestres pode estar relacionada com mudanças climáticas no passado. Apesar dos processos de biodegradação que, na grande maioria, ocorrem na coluna aquática e na interface sedimento-água, esses compostos são encontrados bem preservados em sedimentos oceânicos. Nesse trabalho, a distribuição relativa desses compostos é empregada como uma ferramenta para avaliar mudanças no transporte de material terrestre para o mar em paralelo às variações climáticas durante os intervalos glaciais e interglaciais. As mudanças na distribuição dos biomarcadores foram estimadas em dois testemunhos coletados ao leste do Atlântico Norte e que correspondem aos últimos 210 mil anos. Os resultados mostraram uma boa correlação entre a distribuição dos biomarcadores e outros parâmetros paleoclimáticos previamente avaliados nos perfis, sugerindo que alguns grupos específicos de compostos orgânicos são importantes indicadores de aporte terrestre para ornar

    Application of Headspace Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry (HS-SPME-GC/MS) on the Evaluation of Degradation Efficiency of Phenolic Compounds and Identification of By-Products from Produced Water

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    Application of the headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GC/MS) technique as an analytical tool to monitoring the degradation of phenolic compounds and the formation of by-products in produced water by UV photolysis and UV/peroxide is proposed. All of the experimental conditions for the degradation tests were carried out according to the response of the surface modeling methods developed. The direct photolysis and the UV/H2O2 processes were capable to degrade more than 99% of the initial concentrations of total phenolic components of produced water. The main by-product found was 2,6-di-tert-butylbenzoquinone (DBQ). The presence of DBQ and other hydroxy compounds, constituting the major fraction of by-products identified, demonstrates that the degradations are initiated by the oxidation of the aromatic phenolic ring generating quinones, diphenols, benzoic acids and phenones

    Photochemical Degradation of Diesel Oil in Water: a Comparative Study of Different Photochemical Oxidation Processes and their Degradation By-Products

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    This paper provides a comparative study of different photochemical oxidation processes and a detailed characterization of the by-products of diesel oil degradation performed using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS). Diesel degradation was conducted in a photolytic reactor using UV, H2O2, UV/H2O2, O3 or O3/UV. The best conditions for each process were obtained applying multivariate analysis and the experimental results indicated that the O3/UV process was the most feasible for the treatment of wastewater containing diesel fuel, with a degradation percentage of > 90%. Almost complete degradation of the aromatics was achieved. Phenolic compounds were identified as by-products of the diesel samples treated with the UV, H2O2, O3 and O3/UV processes. Besides the phenolic compounds, other by-products identified included carboxylic acids and ethers in the UV/peroxide treatment, ethers in the UV irradiation treatment and ketones in the ozone treatment
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