Taís Freitas da Silva

Distribution of polycyclic aromatic hydrocarbons in surface sediments and waters from Guanabara Bay, Rio de Janeiro, Brazil

Polycyclic aromatic hydrocarbons (PAHs) were identified and quantified in sediment and water samples from 12 sites in the north-northeast region of the Guanabara Bay. The samples were analyzed by GC-MS to assess the degree of contamination by monitoring the affected ecosystem after an oil spill that occurred in January 18, 2000. Total PAH concentrations ranged from 77 to 7,751 µg kg-1 dry weight in surficial sediment samples and from not detected to 1592 ng L-1 in water samples. The majority of sediment samples were classified as highly contaminated (total PAH > 500 µg kg-1) while for water samples the concentration of PAHs was not sufficiently high to induce acute toxicity to aquatic organisms. In comparison with other coastal areas, PAH concentrations in Guanabara Bay are relatively high. The ratios of low molecular weight/high molecular weight (LMW/HMW) PAHs, phenanthrene/anthracene and benzo[a]anthracene/chrysene, are sensitive indicators of the origin of PAH pollution, which have shown to be mostly from fuel combustion in the Guanabara Bay.

Polycyclic aromatic hydrocarbons (PAHs) in burning and non-burning coal waste piles

The coal waste material that results from Douro Coalfield exploitation was analyzed by gas chromatography with mass spectrometry (GC-MS) for the identification and quantification of the 16 polycyclic aromatic hydrocarbons (PAHs), defined as priority pollutants. It is expected that the organic fraction of the coal waste material contains PAHs from petrogenic origin, and also from pyrolytic origin in burning coal waste piles. The results demonstrate some similarity in the studied samples, being phenanthrene the most abundant PAH followed by fluoranthene and pyrene. A petrogenic contribution of PAHs in unburned samples and a mixture of PAHs from petrogenic and pyrolytic sources in the burning/burnt samples were identified. The lowest values of the sum of the 16 priority PAHs found in burning/burnt samples and the depletion LMW PAHs and greater abundance of HMW PAHs from the unburned coal waste material relatively to the burning/burnt material demonstrate the thermal transformation attributed to the burning process. The potential environmental impact associated with the coal waste piles are related with the release of petrogenic and pyrolytic PAHs in particulate and gaseous forms to soils, sediments, groundwater, surface water, and biodiversity.

Organic Facies: Palynofacies and Organic Geochemistry Approaches

The concept of organic facies, as well as the definitions and means of the different facies became a very important tool to palaeoenvironmental characterization, basin analysis and fossil fuel exploration. The application of this concept is the best way to integrate microscopy and geochemical techniques to study kerogen contained in sedimentary rocks. Thus, palynofacies analysis and bulk geochemical methods (organic facies) are used to characterize the sedimentary organic matter (kerogen and bitumen). Palynofacies analysis involves the integrated study of all aspects of the kerogen assemblage: identification of the individual particulate components, assessment of their absolute and relative proportions and preservation states. The correlation between palynofacies and geochemical data provides the organic facies models that point out the depositional environmental conditions and hydrocarbon source rock potential.

Polycyclic Aromatic Hydrocarbons in Fishes and Sediments from the Guanabara Bay, Brazil

Polycyclic aromatic hydrocarbons (PAHs) were identified and quantified in sediment and fish samples. The samples were analyzed by gas chromatography/mass spectrometry to gather information about the degree of contamination. PAH total concentration ranged from 79 to 487 μ g/kg dry weight in surficial sediment samples and from 4 to 53 μ g/kg in fish samples. Most sediment samples were classified as fairly contaminated (at 250–500 μ g/kg of total PAH). The lowest and highest Σ PAH concentrations in fish (4 to 53 μ g/kg) were found for Mugil lisa and Micropogonias furniere, respectively. The PAHs in sediment and fish samples are derived primarily from mixed sources.Polycyclic aromatic hydrocarbons (PAHs) were identified and quantified in sediment and fish samples. The samples were analyzed by gas chromatography/mass spectrometry to gather information about the degree of contamination. PAH total concentration ranged from 79 to 487 μ g/kg dry weight in surficial sediment samples and from 4 to 53 μ g/kg in fish samples. Most sediment samples were classified as fairly contaminated (at 250–500 μ g/kg of total PAH). The lowest and highest Σ PAH concentrations in fish (4 to 53 μ g/kg) were found for Mugil lisa and Micropogonias furniere, respectively. The PAHs in sediment and fish samples are derived primarily from mixed sources.

Avaliação geoquímica de biomarcadores ocluídos em estruturas asfaltênicas

Asphaltenes from two Brazilian crude oils were submitted to mild oxidation to disrupt their structure, releasing the occluded oil. The released hydrocarbons were compared with those from the original crude oil, and used to evaluate the alteration of the oils, especially as a result of biodegradation, but also thermal maturity. The crude oils used are depleted in n-alkanes, which are usually related to biodegradation. However, the released products from the corresponding asphaltenes have n-alkane distributions from nC10 to nC40, suggesting a protection effect from biodegradation. The m/z 191 mass chromatograms showed higher relative intensities for tricyclic terpanes than the hopanes in the crude in comparison with the released ones.

Low diagnostic yield of invasive coronary angiography: is the noninvasive stress testing guilty? Data from a cohort of 2600 patients

Purpose: Many patients referred for invasive coronary angiography (ICA) following clinical assessment complemented with noninvasive stress testing (NIST) do not have obstructive coronary artery disease (OCAD). We aimed to determine the predictors of OCAD and the incremental value of NIST. Methods: We analyzed a cohort of patients referred for ICA for stable CAD diagnosis in a single tertiary-care center (2006-2011). Traditional and nontraditional CAD risk factors, modified Framingham risk score (FRS), symptoms, left ventricle function (LVF), NIST and ICA results were assessed. OCAD: luminal narrowing ≥70% (≥50% for left main artery). OCAD predictors were determined by uni and multivariate analysis. To assess the incremental predictive value of each factor, a stepwise logistic regression analysis was performed, starting with (1) FRS and progressively adding (2) nontraditional risk factors, (3) symptoms, (4) pretest (NIST) probability of CAD, (5) LVF and (6) NIST result. The discriminatory power at each step was evaluated by the area under the ROC curve (AUC). Results: 2600 patients included: 65.2±9.9 years, 59% male, mean 10-year Framingham risk 18%, 10% depressed LVF, 81% positive NIST (treadmill exercise ECG/SPECT). Only 49% had OCAD. Factors independently associated with OCAD: class 3 (CCS) angina (OR 5.3, 95% CI 3.1-8.9), typical angina (OR 3.2, 95% CI 2.6-4.1), male gender (OR 2.9, 95% CI 2.4-3.7), depressed LVF (OR 2.9, 95% CI 1.9-4.3) and high FRS (OR 1.2, 95% CI 1.1-1.2), (all p<0.05). Stepwise analysis shown in the Figure. ![Figure][1] Conclusions: The diagnostic yield of ICA was low. The single most important predictor of OCAD was severe angina, while NIST did not increase the discriminatory power over the clinical judgment. Better strategies are needed to avoid unnecessary referrals to ICA. [1]: pending:yes