Authors:M. Vasconcellos, M. Saiki, D. Fávaro, V. Maihara, A. Figueiredo, and M. Catharino
The Research Reactor Center (CRPQ) of IPEN/CNEN-SP operates the IEA-R1 Research Reactor, at a nominal power of 2 MW thermal,
on a 64 hour per week continuous cycle. The IEA-R1 is a pool type reactor, moderated and cooled by light water, with graphite
as a reflector. One of the main activities of CRPQ is the neutron activation analysis, which is applied to many fields of
research, in collaboration with other institutes and universities. The Research Reactor installations are also intensely used
for human resources development in the field of radiochemistry and neutron activation analysis, at graduate and post-graduate
levels. In the present paper, an overview will be presented of some of the neutron activation analysis research lines that
are being developed, comprising environmental and health-related applications.
Authors:V. Maihara, I. Gonzaga, V. Silva, D. Fávaro, M. Vasconcellos, and S. Cozzolino
Due to its essential characteristics, the daily dietary selenium intake of individuals should be monitored accurately. In
the current work, daily selenium intake of different Brazilian population groups based on duplicate portion diet analysis
was evaluated and compared with the new estimated average requirement values (EAR), to assess if selenium deficiency or excess
could be observed in these groups. Selenium content was determined by neutron activation analysis (NAA). The average daily
dietary selenium intake found was 26.3 (±8.3) ·g/day for children from the city of São Paulo, 37.4 (±16.0) ·g/day for children
from Belém, 107 (±107) ·g/day for children from Macapá, 28.4 (±7.5) ·g/day for institutionalized elderly, 32 (±6) ·g/day for
non-institutionalized elderly and 37 (±17) ·g/day for university students from São Paulo. Most daily dietary selenium intake
range observed were below the EAR values. The values obtained for children groups from Belém and Macapá cities, whose intake
levels were much higher than the recommendation, were an exception.
Authors:M. Vasconcellos, V. Maihara, D. Favaro, M. Armelin, E. Toro, and R. Ogris
The present paper describes radiochemical separation procedures developed for the determination of the elements As, Cr, Hg, Sb and Se in biological reference materials. The methods chosen utilize ion exchange, retention on inorganic exchangers and solvent extraction techniques for the isolation of the elements of interest. These procedures are more rapid than previously used methods, such as distillation and precipitation. As to the sample dissolution, the following procedures were tested using radioactive tracers and reference materials: treatment of the materials in teflon bombs with a mixture of HNO3+H2SO4 or HNO3 only in a normal oven, and with HNO3 in a microwave oven using specially designed digestion bombs.
Authors:M. Vasconcellos, P. Bode, G. Paletti, M. Catharino, A. Ammerlaan, M. Saiki, D. Fávaro, A. Byrne, R. Baruzzi, and D. Rodrigues
Biomonitoring of mercury contamination of Brazilian Indian population groups living in the Xingu Park, a reservation situated in the Amazonic region, has revealed very high levels of mercury in hair samples as compared to controls. Total mercury was determined by INAA in most of the tribes living in the Park and methylmercury was determined by CVAAS in samples with total mercury above 10 mg/kg. Due to the fact that selenium seems to protect animals against the toxic effects of methylmercury, it was considered also of interest to determine its concentrations in the hair samples with very high mercury levels. Selenium was determined by INAA via the short-lived radionuclide 77mSe (T1/2 = 17.45 s). The correlations between selenium and mercury concentrations in Brazilian controls and in the Indian population groups are discussed.
Authors:C. Gonçalves, D. Fávaro, A. Melfi, S. de Oliveira, M. Vasconcellos, A. Fostier, J. Guimarães, R. Boulet, and M. Forti
In the present work, results from a survey on mercury concentration in sediments and soils from a gold mining area along the Vila Nova river, in Amapá State, Brazil, are presented. These values were compared with those from the Igarapé Pedra Preta basin, an area unaffected by mining activities. Total mercury contents were determined in the muddy (silt+clay) fraction of the sediments and in the <2 mm fraction of the soils using radiochemical neutron activation analysis (RNAA). The detection limit of the method was 54 µg·kg–1 for soils and 14 µg·kg–1 for sediments when 200 mg of sample were analysed. The Hg results obtained from a comparison between our current method (RNAA) and CV AAS are also presented. Mercury levels showed to be very high in the soils and sediments collected in the Vila Nova river (up to 2 mg·kg–1) when compared to background values (0.3 mg·kg–1) for this region. An enrichment factor was calculated, using Al as a normalizing factor. It showed values up to 8 in sediments of the Vila Nova river basin, indicating a relatively high degree of pollution as compared to the values of about 1 for the samples of the Igarapé Pedra Pretra basin.
Authors:D. I. T. Fávaro, S. R. Damatto, P. S. C. Silva, A. A. Riga, A. Y. Sakamoto, and B. P. Mazzilli
Pantanal, located in the central region of South America, is recognized as one of the world's largest freshwater wetlands.
In order to verify possible changes in this environment, a study was undertaken in Nhecolândia Pantanal, Mato Grosso do Sul
State, Brazil. Two sediment cores from the Salina do Meio pond (SM1 and SM2) and one core from a small flood land named Baía
(B5) were collected in 2001. The elements As, Ba, Br, Ce, Co, Cr, Cs, Eu, Fe, Hf, La, Lu, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb,
Th, U, Yb, Zn and Zr were determined by instrumental neutron activation analysis (INAA). Cluster and factorial analysis were
applied to the chemical data. The sedimentation rate in the SM2 core was determined by 210Pb method and the mean value found was 0.61 cm . y-1. The results obtained in the present study showed that recent geochemical processes such as desorption, precipitation and
dissolution can contribute for the high water alkalinity and salinity in the saline ponds.
Authors:L. A. Farias, D. I. T. Favaro, V. A. Maihara, Vasconcellos M. B. A., L. K. Yuyama, J. P. L. Aguiar, and F. J. Alencar
Daily dietary intake of Hg and some essential elements in diets of children from communities in the Jaú National Park, Amazon
region, were assessed. Diet samples were analyzed for total Hg content using cold vapor atomic absorption spectrometry and
Ca, Fe, K, Na, Se and Zn contents by instrumental neutron activation analysis. The weekly tolerable provisional intake for
Hg in the communities studied varied from 13 to 57 mg of Hg per kg of body weight, exceeding the limit of 5 mg . kg-1 set by the WHO. Comparison of the daily dietary intake values to the new Dietary Reference Intakes (4-8 years), showed prevalence