Navegando por Orientadores "KAWAKAMI, Silvia Keiko"

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Acesso aberto (Open Access)
Aplicação da cromatografia líquida de alta eficiência na investigação de hidrocarbonetos policíclicos aromáticos em testemunhos sedimentares
(Universidade Federal do Pará, 2013-07-31) EVANGELISTA, Camila do Carmo Pereira; KAWAKAMI, Silvia Keiko; http://lattes.cnpq.br/5306256489815710
Polycyclic aromatic hydrocarbons are organic (PAH) compounds originated from natural or anthropogenic sources and are considered priority substances by environmental agencies because of carcinogenic and mutagenic potentials. Therefore, rapid and low cost analytical methods for these compounds are of significant relevance for environmental purposes. The present study aimed the optimization of an analytical method for PAHs using High Performance Liquid chromatography with a diode array detector (HPLC-DAD) for the application to an estuarine sediment core. For the optimization and evaluation of the method, a sedimentary column measuring 46 cm length was collected at the mouth of the Igarapé Tucunduba (Belém, Pará) and sectioned in 2 cm portions. After dryness, 30 g of each portion were extracted with a mixture of dichloromethane in acetone in ultrasound bath for 40 min. the extracts obtained were centrifuged, purified on silica gel as a clean-up adaptation mainly to retained fine particles, then concentrated using vacuum evaporator and filtered through 0,2 μm nylon membrane before HPLC injection. Samples spiked with 16 PAH analytical standards and procedural blanks were processed on the same way. The parameters assessed showed: (1) good linearity, the calibration curves presented high correlation coefficients ; (2) adequate accuracy: relative standard deviations within acceptable values with 2,1% for acenaphthylene and maximum of 19,7% for fluoranthene; (3) low detection limits between 0,004 to 1,085 ng g-1 which make in situ determinations feasible; (4) adequate recovery for traces with minimum of 40,0% for acenaphthylene and maximum of 103,1% for benzo(k)fluoranthene. The total PAH concentration in the sediment core ranged between 60,77 to 783,3 ng g-1 dry sediment. The optimized method showed advantages over the traditional methods based on soxhlet extrations and clean up adsorption columns in terms of time of analysis and reduced costs with the use of smaller amounts of solvents. The limitation, however, was de coelution of some compounds, which is probably due to the low efficiency of the chromatographic column that was available at the time of the analysis. The method was applicable to estuarine complex samples, rich in silt and clay. Diagnostic ratios using parental PAHs indicated petrogenic sources at 24 - 26 cm and 28 – 30 cm depth; and pirolitics sources at 6 - 8 cm, 10 - 12 cm , and 14 - 16 cm respectively.
Acesso aberto (Open Access)
Esteróides como biomarcadores de contaminação orgânica em sedimentos superficiais e testemunhos do Estuário Guajará-PA
(Universidade Federal do Pará, 2012-06-13) GOMES, Heyde Gonçalves; SOUZA FILHO, Pedro Walfir Martins e; http://lattes.cnpq.br/3282736820907252; KAWAKAMI, Silvia Keiko; http://lattes.cnpq.br/5306256489815710
The city of Belém of Pará, its surroundings and body waters are subject to environmental impacts due to the increase of local population and poor sanitation conditions. The Guajará bay receives untreated sewage effluents from Belem’s catchment area, which is of concern to public health and environmental quality. This study aimed to identify organic contamination in surface sediments and sediment cores of the Guajará estuary using steroids as biomarkers. Steroids have been used since 1960 as tracers of natural and anthropogenic organics in the aquatic environment, however, studies using such compounds in the northern region of Brazil is new. Therefore data from other regions were important for comparison and to improve our knowledge about the composition of organic matter in the Guajará Bay. Samples of surface sediments and sediments cores (~50 cm) were collected in January 2011. The sediments cores were taken from Tucunduba, Icoaraci. Surface sediments were collected in Tamandaré, Porto da Palha, Ver-o-Peso, and Miramar. Steroid analyses were performed using gas chromatography with flame ionization detection. Sediments were subsampled for analysis of chlorophyll, total organic carbon and grain size. Several steroids were identified (coprostanol, cholesterol, epicoprostanol, colestanol, colestanona, coprostanona, estigmasterol, brassicasterol, β-sitosterol, β-sitostanol), from both natural and anthropogenic sources. Concentrations of coprostanol, an sterol of fecal origin, in surface samples ranged from 0.06 to 5.61μg g-1 and in the sediments cores of Tucunduba, 0.02 to 11.23 μg g-1 and Icoaraci 0.03 of 0.31 μg g-1. For the surface sediment samples, highest coprostanol concentrations were observed at Ver-o-Peso, in contrast to the high sand content of the sediments. For the sediment cores, two different profiles were observed: for Tucunduba the steroids that predominated at high concentrations within the top layers were coprostanol, coprostanona, colesterol e colestanol, which indicated recent sewage inputs. For Icoaraci, brassicasterol, estigmasterol, sitosterol e sitostanol, steroids of plant sources predominated at higher concentrations. Absolute coprostanol concentrations and steroid concentration ratios indicated that most of the sampling sites were contaminated by untreated sewage. The use of steroid ratios to understand the results was also important to minimize the dependence of the steroids to organic carbon content and granulometry.