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  • Author or Editor: D. Fávaro x
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Abstract  

The distribution constant KD(HTTA) of thenoyltrifluoroacetone between 10–3M HNO3 and cyclohexane was determined by means of spectrophotometric measurements of HTTA concentration in the aqueous phase. The distribution ratio, D, of HTTA, when tri-n-octylphosphine (TOPO) is present, and the equilibrium constant, n , of the reaction between HTTA and TOPO in the organic phase were also determined. By means of the known KD(HTTA) and D values, the equilibrium constant of the HTTA-TOPO interaction was calculated. Making use of KD(HTTA) and n values and of the slope analysis method, the composition of the extracted lanthanide complexes was established. By considering the interaction reaction between the extractants, the species Ln(TTA)3 · TOPO and Ln(TTA)3 · 2(TOPO), for Ln=La and Yb, were identified in the organic phase. The equilibrium constants of the reactions that give rise to the species were also calculated.

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Summary  

Phosphate deposits are generally characterized by enhanced radionuclide concentrations compared to natural levels. The mining and processing of this phosphate ore redistribute radionuclides throughout the environment and introduce them into phosphoric acid and phosphogypsum. Phosphoric acid is the starting material for triple superphosphate (TSP), single superphosphate (SSP), monoammonium phosphate (MAP), diammonium phosphate (DAP), NPK fertilizers and di-calcium phosphate (DCP). Contents of natural radionuclides from thorium and uranium series, 226Ra, 210Pb and 228Ra, were measured in Brazilian igneous phosphate rock, phosphoric acid, phosphogypsum and phosphate fertilizer samples, using high-resolution gamma-spectrometry. Neutron activation analysis was used for the determination of U and Th in the same samples. The fertilizers samples which are derived directly from phosphoric acid, MAP and DAP, presented activity concentrations around the detection limits of the counting system for 226Ra (<5.0 Bq . kg-1 ), for 228Ra (<3.0 Bq . kg-1) and for 210Pb (<19 Bq . kg-1). As for U and Th, the concentrations found in MAP and DAP are more significant, up to 374 and 250 Bq . kg-1, respectively. SSP, TSP and NPK, which are obtained by mixing phosphoric acid with different amounts of phosphate rock and NH3, presented higher concentrations of radionuclides, up to 871 Bq . kg-1 for 226Ra, 283 Bq . kg-1 for 228Ra, 1255 Bq . kg-1 for 210Pb, 413 Bq . kg-1 for U and 538 Bq . kg-1 for Th.

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Summary  

Santos Basin, located in Southwest Brazil, is considered the most important industrial region of the country. Among the industrial activities present, phosphate fertilizer plants are responsible for the production of 69 million tons of phosphogypsum waste, which is stockpiled in the surrounding environment. This waste concentrates radionuclides of the natural series as well as rare earth elements originally present in the phosphate rock used as raw material. This study aims to evaluate the environmental impact of such activities in the sediments of the estuarine system by measuring the concentration of U, Th and rare earth elements and activity concentration of radionuclides 226Ra, 228Ra, 228 Th and 210Pb.

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Abstract  

Excess dietary intake may increase the risk for the hyperthyroidism in the elderly. This study investigated iodine dietary intake by epithermal neutron activation analysis (ENAA) analyzing duplicate portion diet and fortified table salt samples. Duplicate diet samples were obtained from a group of twenty-five steel mill workers from the city of São Paulo, over a 3-day period. The samples were freeze dried, mixed and homogenized. Fortified table salt brands were collected from the market and were analyzed with no pre-treatment. Assays for the iodine concentration in the table salt samples revealed values between 24 to 65 mg/kg. The average iodine daily intake for the worker’s diets was 813 μg/day, ranging from 402 to 1363 μg/day. In some cases daily intakes were around 10 times higher than the recommended dietary allowance (RDA) value (150 μg/day).

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Abstract  

Twenty six bottom sediment samples were collected from the Cananéia estuary in summer and winter of 2005. Multielemental analysis was carried out by instrumental neutron activation analysis. Total mercury was determined by cold vapor atomic absorption. As, Cr, Hg and Zn concentrations were compared to the Canadian oriented values (TEL and PEL). Sample points 4 and 9 presented higher concentration for most elements and As and Cr exceeded the TEL values. Organic matter (>10%) associated with siltic and clay sediments was observed. Climatic conditions, hydrodynamic and biogeochemical processes promote differences in seasonal concentrations of elements at some points, which contribute to special distributions.

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Abstract  

Since the early days of mankind, plants have been used as food and for medicinal purposes. Still, little information exists in literature about the activity concentration of 238U and 232Th decay products, as well as stable element concentrations in Brazilian plants. Activity concentrations of 226Ra, 228Ra and 210Pb, and chemical concentrations of As, Ba, Br, Cs, Co, Cr, Cu, Eu, Fe, Hf, La, Lu, Rb, Sb, Sc, Sm, Ta, Tb, Yb, Zn and Zr were determined in ten samples commonly used in Brazilian medicinal plants.

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Abstract  

Radiochemical procedures for the analysis of 210 Pb and 210 Po in foods and diets are presented. Because of the low beta energy of 210 Pb, its analysis was based on a separation of the daughter radionuclide 210 Bi by precipitation of lead sulphate, 210 Bi ingrowing and beta counting of this nuclide. 210 Po analysis was based on wet dissolution of the sample, deposition onto silver disc and counting by alpha-spectrometry. Levels of these radionuclides in individual items and diets of selected university students were determined in order to evaluate the intakes of 210 Pb and 210 Po as well as the dose due to ingestion of foods and diets in São Paulo city.

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Abstract  

The Rio Grande reservoir lies southeast of the Metropolitan Area of São Paulo. In order to evaluate if the sediments contain a historical registration of anthropogenic activity, four sediment cores were sampled from the reservoir. In these cores the Hg concentration was determined by the CV AAS technique, major and trace elements by instrumental neutron activation analysis and the sedimentation rates by the 210Pb method. The results obtained for Hg are much higher than expected, showing an anthropogenic contribution. As a general trend, the elemental concentration decreases with depth, indicating recent contamination.

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Abstract  

Instrumental neutron activation analysis (INAA) was applied to determine the elements Br, Ca, Cl, Cu, Fe, I, K, Mg, Mn, Na, Rb, S, V, Zn in five varieties of Brazilian corn, resulting from the studies carried out in order to increase their protein contents. The accuracy of the method was evaluated by means of reference material analysis. In general, the precision of the method was lower than 15%, except for Cu, I and S. Sensitivity and detection limit were also determined. Besides, tryptophan contents were determined. It was observed that the tryptophan content in improved corn samples was twice as large as in the normal samples. However, the same ratio was not observed in the inorganic element contents.

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Abstract  

The present paper describes radiochemical separation procedures developed for the determination of seven elements: As, Cd, Cr, Cu, Hg, Sb and Se in different Brazilian regional diets. In the case of the elements As, Hg, Sb and Se, the procedure was based on retention in inorganic exchanger TDO (tin dioxide) and determination of Hg by extraction with Ni(DDC)2. For determination of Cd, Cr, Cu and Se the procedure chosen was based on retention in inorganic exchanger HMD (hydrated managese dioxide) and extraction of Cu and Cd as diethyldithiocarbamate compounds. The accuracy and precision of the methods studied were tested by means of analyses of different reference materials. Due to the lack of data on trace element levels in Brazilian foodstuffs and diets, these methods were applied to determination of these elements in different Brazilian regional diets. These diets were supplied by the Food and Experimental Nutrition Department of the Faculty of Pharmaceutical Science, University of São Paulo. The daily dietary intake values for these diets are presented for As, Cd, Cr, Cu, Hg, Sb and Se.

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