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  • Author or Editor: B. Mazzilli x
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Abstract  

The bioaccumulation of zinc byPoecilia reticulata from water as well as the elimination of the metal previously absorbed were determined by using65Zn as radioactive tracer. The exposure time varied from 18 days to 30 days. The results obtained show that the absorption and elimination of zinc byPoecilia reticulata is slow, 30 days being necessary for the elimination of 70% of the previously absorbed zinc. The same experiment was also carried out by feeding fish with65Zn contaminated food. The results obtained show that in 30 days only 40% of the zinc previously absorbed is eliminated by the fish.

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Abstract  

The distribution coefficients (Kd) for134Cs,60Co and234Th were determined experimentally in order to foresee the fate of these radionuclides discharged to Pinheiros River by IPEN's facilities. The parameters studied in the laboratory were the effect of pH, aerobic condition and the time of contact. The results obtained experimentally confirm the predictions that the cesium is slowly retained by the sediment along the Pinheiros River. The retention of cobalt, which is an unstable element, is affected by variations in the pH. Thorium is almost completely retained in the vicinity of the discharge point.

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Abstract  

The determination of 14 trace elements /Ba, Ce, Co, Eu, Fe, Hf, La, Nd, Rb, Sb, Sc, Sm, Tb and Th/ has been carried out in three different brands of Brazilian cigarettes. The samples and standards were irradiated for 8 h at a thermal neutron flux of approx. 5×1012 n cm–2s–1. After the irradiation, the -rays activity was measured on a Ge/Li/ detector coupled with a 4096-channel pulse height analyzer. The results were compared with those obtained for the tobacco from American, Iranian, Turkish, Pakistan and Yugoslavian cigarettes. The amount of each element transferred to the ashes was determined.

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Abstract  

Concentrations levels of uranium and thorium isotopes have been analyzed in the m mineral spring waters of a high background region of Brazil: Poços de Caldas and Águas da Prata. The procedure was based on the determination of238U,234U,232Th,230Th and228Th by -spectrometry after separation and purification of the isotopes of interest by using anion-exchange chromatography and preparation of the samples for -measurements by electrodeposition. The concentration varied from <1.1 to 28.4 mBq.l–1 and from <1.6 to 141 mBq.l–1 for238U and234U, respectively. Thorium isotope measurements varied from <0.2 to 1.8 mBq.l–1 from <0.3 to 4.9 mBq.l–1 and from <0.8 to 19.9 mBq.l–1 for232Th,230Th and228Th, respectively. Calculations of thorium and uranium isotopic activity ratios were carried out giving values ranging from 1.9 to 7.2, from 1.2 to 3.0 and from 7.7 to 15.3 for234U/238U,230Th/232Th and228Th/232Th, respectively. The effective doses due to the intake of238U and234U present in these waters are expected to reach values up to 1.4×10–3 mSv y–1 and 8.0×10–3 mSv y–1, respectively.

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Abstract  

The phosphate rocks used for the production of phosphate fertilizers present in their composition radionuclides of the U and Th series. During the chemical attack, the radionuclides are distributed to final products and phosphogypsum. A sequential radiochemical procedure was implemented to determine the content of radionuclides alpha emitters in samples of fertilizers and phosphogypsum produced in Brazil. The results obtained show that the levels of radioactivity present in the fertilizers are of the same order of magnitude on those found in the phosphogypsum, reaching values up to 1158 and 457 Bq kg−1, for the U and Th series, respectively.

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Abstract  

In the present work, a comparative study is made among nuclear methods for235U/238U ratios determination: activation analysis followed by high-resolution gamma-ray spectrometry, delayed neutron counting, passive gamma-ray and alpha spectrometry. Activation analysis followed by high-resolution gamma-ray spectrometry yielded a relative standard deviation down to 0.1% and a relative error of about 1% for standards of uranium enriched to 14%. Passive gamma-ray spectrometry using Ge(Li) detectors yielded a relative error down to 0.1% for enriched uranium and values even lower for the standard deviation. Passive gamma-ray spectrometry using Low Energy Photon Detector (LEPD) yielded a precision of 0.2% and a still better accuracy for enriched standards. In the case of alpha spectrometry, a relative error down to 0.5% and a precision of about 1% were obtained, also for enriched uranium standards. Delayed neutron counting allowed a relative standard deviation of about 7% and a relative error of about 2%, for standards of depleted uranium.

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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  

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  

Using instrumental neutron activation analysis, the vertical distribution of La, Ce, Nd, Sm, Eu, Tb, Yb and Lu was determined in 3 well dated sedimentary cores collected from Laguna Mar Chiquita, Argentina. Validation of the methodology was done using the Soil 7 (IAEA) reference material. The REE contents vary according to core location and lithological units, depending on the proportion of fluvial terrigenous components in the lake sediments. Lithologies with higher proportion of terrigenous components show higher REE concentrations, suggesting that the dominant REE carrier phase might be a detrital mineral. There is a consistent value of about 1.2 for (La/Yb)N and (LREE/HREE)N ratios for all sediments at the three sites, indicating a slight LREE enrichment in relation to the average shale NASC. Ce/Ce* values are close to 1.0, meaning that Ce behaves similarly to other light REE's.

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Summary  

In the last decades considerable attention has been given to technologically enhanced natural occurring radioactive material (TENORM). Within this frame, of particular concern is the phosphate fertilizer industry, located in Cubatão, São Paulo State, Southwest Brazil. This industry is 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 originally present in the phosphate rocks used as raw material. This study aims to evaluate the environmental impact of such activities in the sediments of the estuarine system. Contents of natural radionuclides from thorium and uranium series were measured in sediments from Cubatão estuarine system, using high-resolution gamma-spectrometry. U and Th were determined by instrumental neutron activation analysis (INAA). It was observed that U and Th concentration is higher in the rivers close to the phosphogypsum piles, at least five points were identified as being affected by anthropogenic factors.

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