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Navegando por Autor "OLIVEIRA, Geiso Rafael Fonseca"

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    Determinação espectrofotométrica do arsênio em solo da cidade de Santana-AP usando o método do dietilditiocarbamato de prata (SDDC) modificado
    (Instituto Nacional de Pesquisas da Amazônia, 2009) PEREIRA, Simone de Fátima Pinheiro; OLIVEIRA, Geiso Rafael Fonseca; OLIVEIRA, Johny da Silva; SILVA, Juliane da Silva e; SOUSA JUNIOR, Pedro Moreira de
    Several tons of manganese residues containing arsenic, generated by a mining company, were used as streets landfill in Santana-Ap city. The possibility of exposure of people living in these villages has led to the study of quantification of total arsenic in the soil. After digestion, the levels of arsenic were quantified by molecular absorption spectrophotometry using a hydrides generation automatic system (HG-MAS), dicyclohexilamine/CHCl3 as silver diethyldithiocarbamate (SDDC) solvent and KBH4 as reducer. The method presented good results with sensitivity (ε) of 1.10 104 l.mol-1.cm-1, stability of 2.96 % and other advantages in relation to the official method. The method was applied to the soil standard samples with recoveries of the 98.82 % (n=10). The soil analysis showed that 94.74 % samples showed arsenic concentrations above the value published by CETESB for residential land (50 mg.kg-1) with the average value of 682.96 mg.kg-1, ranging of 48.08 mg.kg-1, at 1,713.00 mg.kg-1 shows that the soil arsenic contamination.
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    Distribuição de elementos tóxicos no estuário do rio Amazonas
    (2011) PEREIRA, Simone de Fátima Pinheiro; PIRES, Otílio Othon; SARAIVA, Augusto Cesar Fonseca; OLIVEIRA, Geiso Rafael Fonseca; SOUSA JUNIOR, Pedro Moreira de; MIRANDA, Rafaella Galvão; SILVA, Cléber Silva e; SALES, Reginaldo da Silva
    The non-essential elements found in the superficial waters of the Amazon River is a global worry since the local hydric resources represent the world's largest fresh water reservoir. This research aimed at studying the occurrence of As, Al, Mn and Pb in the waters of the Amazon River estuary. The 84 samples in three depths were collected in three different regions: North Channel of the Amazon River, in the state of Amapá; South Channel of the Amazon River, in the state of Pará; and Pará River, also in the state of Pará. Inductively coupled plasma atomic emission spectrometry (ICPAES) method was employed to determine the concentrations of Al, Mn and Pb in the samples while hydride generation atomic absorption spectrometry (HGAAS) method was employed in determining their As concentrations. As concentrations varied from <0.35 to 50.60 µg/L; Al concentrations varied from <1.88 to 3347.70 µg/L; Mn concentrations varied from <1.92 to 403.39 µg/L; and Pb concentrations varied from <0.18 to 51.96 µg/L. On average, the concentrations of As (samples from the South Channel), of Al (samples from the three regions), of Mn (samples from the North Channel and from the South Channel), and of Pb (samples from the North Channel) were higher than allowed by the Brazilian legislation. The origin of the elements can be anthropogenic due to mining and industrial activities as well as natural due to decomposition of igneous rocks from the drainage basin of the Amazon River which releases the element linked to the suspended particulate matter. High concentrations of toxic elements, especially of As and Pb, put the health of the populations who consume water of the Amazon River and the Pará River at risk.
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    Spectrophotometric determination of arsenic in soil samples using 2-(5-bromo-2-pyridylazo)-5-di-ethylaminophenol (Br-PADAP)
    (2008) PEREIRA, Simone de Fátima Pinheiro; FERREIRA, Sérgio Luis Costa; OLIVEIRA, Geiso Rafael Fonseca; PALHETA, Dulcidéia da Conceição; BARROS, Bruno de Cássio Veloso de
    In this paper, a new, simple and sensitive method for arsenic determination in soil is proposed. This is based on the reduction of silver (I) and iron (III) ions by arsine followed by a complexation reaction of iron (II) with the spectrophotometric reagent Br-PADAP 2-(5-bromo-2-pyridylazo)-5-di-ethylaminophenol. Arsenic determination with a Sandell's sensitivity of 3.1 10-4 cm-2, linear range from 0.1 µg ml-1 to 2.0 µg ml-1 (r560 = 0.9995), molar absorptivity of 2.45 105 l mol-1 cm-1 and a concentration detection limit of 1.4 ng ml-1 (3s) were obtained using a 10 ml sample volume. Selectivity was increased with the use of EDTA as a masking agent. The proposed method was applied for arsenic determination in the presence of several ions amounts in digested soil samples. The results revealed that antimony (III), mercury (II), germanium (IV), platinum (IV) interferes at all analyzed proportions. The interferences can be easily removed by the use of EDTA. Precision and accuracy obtained were satisfactory with a R.S.D. < 5 %. Recovery of arsenic in soil samples varied from 95.55 to 102.70 % with a mean of 99.63 %. These results demonstrated that the proposed method is applicable for arsenic analysis in different soil samples.
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