NICOLE PEREIRA DE LIMA

NICOLE PEREIRA DE LIMA

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Avaliação do teor de Cr ao longo do sítio do Observatório Amazônico de Torre Alta (ATTO)
2024 - TAPPIZ, BRUNO; SILVA, PAULO S.C. da; OSTERMANN, CAROLINE K.; LIMA, NICOLE P. de; CARVALHO, ELIAS F. de; BUSTILLOS, JOSE O.V.
A fração mássica do elemento Cr foi analisada amostras de solo coletadas ao longo do sítio do Observatório Amazônico de Torre Alta (ATTO), localizado na Reserva de Desenvolvimento Sustentável (RDS) do Uatumã, a aproximadamente 150 km ao nordeste da cidade Manaus, estado do Amazonas. O sítio ATTO encontra-se em uma região sem desmatamento e com pouca influência antropogênica onde estão instaladas duas torres (as torres ATTO e Instante) dedicadas a pesquisas atmosféricas. A RSD Uatumã é caracterizada por diferentes ecossistemas: (i) Terraço, uma área florestal sazonalmente inundada por água negras (Igapó) ao longo do canal principal e afluentes menores do rio Uatumã; (ii) Platô, região de floresta densa em terras altas e não inundadas (Terra Firme); e (iii) Campina (cerrado em solos de areia branca) que inclui uma zona de transição denominada Campinarana (florestas em solo de areia branca), situadas principalmente entre os Terraços de rio e a encosta em direção ao Platô. Com o intuito de avaliar o teor de Cr ao longo do sítio ATTO, foram coletadas amostras nas 3 diferentes regiões que compõe o sítio de estudo. Ao todo, foram coletadas amostras de solo em 6 pontos do Terraço, 4 na Campina e 6 no Platô, totalizando 87 amostras. As amostras foram analisadas no Instituto de Pesquisas Energéticas e Nucleares (IPEN), pela técnica de Análise por Ativação Neutrônica Instrumental (INAA). Os teores médios de Cr obtidos, em mg/kg, por ponto, para a região do Terraço foram: T1 = 29 ± 1; T2 = 37 ± 1; T3 = 76 ± 2; T4 = 28 ± 1; T5 = 42 ± 1; T6 = 34 ± 1; para Campina e Campinarana: C1 = 2,7 ± 0,1; C2 = 3,4 ± 0,2; C3 = 2,1 ± 0,1; C4 = 2,1 ± 0,2; e por fim, para o Platô: P1 = 85 ± 3; P2 = 69 ± 2; P3 = 66 ± 2; P4 = 102 ± 3; P5 = 101 ± 3; P6 = 99 ± 3. De forma geral, é possível afirmar que os menores teores desse elemento ocorrem na região da Campina e os maiores na região do Platô. Esse comportamento pode ser justificado pela composição geológica predominante em cada região e pelo tipo de intemperismo que afeta a região, denominado intemperismo laterítico. Esse intemperismo ocorre predominantemente em regiões tropicais úmidas, em que ocorre uma lixiviação preferencial dos elementos mais solúveis (como por exemplo os alcalinos e alcalinos terrosos) enquanto que os elementos menos solúveis como o Cr, ficam presos e são enriquecidos no solo. O entendimento da dinâmica do solo na região, por meio do estudo da sua composição elementar, pode contribuir para a compreensão da interdependência existente no sistema solo-biosfera-atmosfera e desse com a relação da floresta com os possíveis efeitos climáticos.
Assessment of 238U and 226Ra activity concentration along the Amazon Tall Tower Observatory site
2023 - TAPPIZ, B.; SILVA, P.S.C.; OSTERMANN, C.K.; LIMA, N.P.; BRAGUIN, L.N.M.; BOTIA, S.; LEVIN, I.; BUSTILLOS, O.V.
The Amazon Tall Tower Observatory (ATTO) site is a region located within the Uatumã Sustainable Development Reserve (USRD), approximately 150 km northeast of Manaus city, in the Brazilian state of Amazonas. At the ATTO site, there are 3 tall towers, which are used for studies on the Amazon rainforest and its interaction with the soil and the atmosphere. The activity concentration of 238U and 226Ra was determined in soil samples collected in the footprint of the ATTO site by gamma spectrometry. The activity concentration of these radionuclides is important for understanding the 222Rn exhalation rate and 222Rn flux from soils. Knowledge of the 222Rn flux at the ATTO site can be useful for applications in atmospheric research, e.g., the 222Rn tracer method can be used to estimate local and regional emissions of greenhouse gasses; simulating 222Rn transport is a powerful tool for evaluation and validation of transport schemes in atmospheric chemical transport models. In this study, 39 samples collected from 13 sampling sites along a transect from the ATTO site to the river were analyzed. The highest activity concentrations were found in the Igapó forest (69 ± 2 Bq/kg for 238U and 47 ± 5 Bq/kg for 226Ra), a region near the Uatumã river with prevailing flooded black-water forest, whereas the lowest activity concentrations occurred in the Campina (Savanna on white-sand soils) and Campinanara (white-sand forest) ecosystems (18 ± 1 Bq/kg for 238U and 13 ± 2 Bq/kg for 226Ra), a transition area located between river terraces and the Terra Firme forest.
Comparison of 238U mass fraction measured by ICP–MS and Instrumental Neutron Activation Analysis techniques
2022 - TAPPIZ, BRUNO; SILVA, PAULO S.C. da; OSTERMANN, CAROLINE; LIMA, NICOLE P. de; ANDRADE, MARIANA N. de; BUSTILLOS, OSCAR V.
Introduction: Uranium is an element present in ambient air, water, soil and rocks [1]. The most abundant natural radioisotope of this actinide (238U) produces in its chain decay the radionuclide 222Rn [2], which is a tracer for atmospheric mixing and transport model validations [3]. The 238U activity concentration in superficial soil samples is a crucial parameter for some 222Rn flux map modeling methodologies [4]. Methods: In this study, 18 superficial soil samples were analyzed. The content of 238U was assessed using two techniques: (i) by the comparative method of the Instrumental Neutron Activation Analysis (INAA) [5] and by ICP–MS (ELAN 6000, PerkinElmer) [6]. Certified Reference Materials (CRM) SRM 1646a Estuarine Sediment and USG STM–2 were used both as comparators in the INAA technique and to ensure quality control. The normality and homoscedasticity of the data were evaluated. Finally, the Mann- Whitney U test [7] was used to assess whether or not there is a significant difference (α = 0.05) between the two techniques. Results: The z-score was calculated to ensure quality control. Z-scores values was obtained by the Modified Horwitz Equation [8], which takes into account the order of magnitude of the content of the analyte and is independent of the CRM uncertainties, unavailable for the CRM used. The z-score values obtained (n = 3) for the radionuclide 238U were 0.5 for the CRM USG STM–2 and -0.4 for SRM 1646a. The z-scores obtained are smaller than 2 therefore they are considered satisfactory [9]. Regarding the statistical parameters of the comparison between the techniques, the normality (Shapiro Wilk) was not verified (p = 0.02 for ICP-MS and p = 0.03 for INAA). The p-value for the test for equal variances (F test) was 0.71 Mann-Whitney U test was used instead of Student’s test due to the non-verification of the normality parameter in the data. The p-value from the Mann-Whitney test (0.51) indicates that there is no significant difference between the 238U content measured by the two techniques. Conclusions: Statistical analysis showed that there is no significant difference between the 238U mass fraction measured by the ICP–MS and the INAA – comparative method. In the future, certified reference materials will also be assessed by ICP–MS in order to corroborate this statistical comparison from a metrological point of view.
Local crystalline structure of doped semiconductor oxides characterized by perturbed angular correlations
2022 - BURIMOVA, ANASTASIA; CARBONARI, ARTUR W.; LIMA, NICOLE P. de; MIRANDA FILHO, ARNALDO A.; SOUZA, ALEXANDRE P. dos S.; SALES, TATIANE da S.N.; FERREIRA, WANDERSON L.; PEREIRA, LUCIANO F.D.; CORREA, BRUNO S.; SAXENA, RAJENDRA N.
Doping semiconductor oxides with trace amounts of non-native elements can improve their properties such as bandgap and conductivity. The lack of local techniques makes the precise characterization of these materials difficult. Among the few techniques capable of providing local characterization, those based on hyperfine interactions at probe nuclei have the advantage of being well established, probing the material homogeneously and completely, thus investigating different regions of material. Some of these techniques are also quite sensitive even at extremely low dopant concentrations. The perturbed angular correlation technique, combined with first-principles calculations, has recently been shown to be a powerful method for characterizing doped semiconductor oxides. In this paper, we present a brief review of the unique information extracted from the semiconductor investigation with such a complex approach, including semiconductor oxides doped with cadmium and other elements. A strong relationship between the local environment, including electronic structure, and the nature of the dopant and the native element of the doped oxides is also shown.
Synthesis and TDPAC characterization of multiferroics
2021 - LIMA, N.P.; BURIMOVA, A.; SOUZA, A.P.S.; LEITE NETO, OSMAR F.S.; CARBONARI, A.W.
Determination of uranium in tree bark samples by epithermal neutron activation analysis
2019 - LIMA, N.P.; SAIKI, M.
In this study uranium (U) concentrations were determined in certified reference materials (CRMs) and in tree bark samples collected in “Cidade Universitária Armando de Salles Oliveira” (CUASO) USP, São Paulo. CRMs were analyzed using the experimental conditions used for barks for analytical quality control of U determina-tion. The barks were collected from different species namely Poincianella pluviosa and Tipuana tipu. These bark samples were cleaned, dried, grated and milled for the analyses by epithermal neutron activation analysis meth-od (ENAA). This method consists on irradiating CRMs, samples and U standard in IEA-R1 nuclear reactor with thermal neutron flux of 1.9 x 1012 n cm-2 s-1 during 40 to 60 seconds depending on their matrices. The U was iden-tified, using gamma-ray spectrometry, by the peak of 74.66 keV of 239U with half-life of 23.47 minutes. Concen-tration of U was calculated by comparative method. Results obtained for CRMs presented good precision and accuracy, with |Z score| ≤ 0.39. Uranium concentrations in tree barks varied from 83.1 to 627.6 ng g-1 and the relative standard deviations of these results ranged from 1.8 to 10 %.
Validação do método de análise por ativação com nêutrons para determinação de urânio em amostras ambientais
2018 - LIMA, NICOLE P. de
O urânio (U) é considerado um elemento poluente do ambiente devido à sua toxicidade química e radiológica, com propriedades cumulativas em seres humanos, podendo causar diversos tipos de doenças no organismo. Consequentemente, há um grande interesse na determinação de U em amostras ambientais devido às ações antrópicas como as emissões desse elemento na mineração, nas indústrias e em acidentes nucleares que ocasionam alterações dos seus teores no meio ambiente. Dentre as diversas metodologias analíticas para a determinação de U em amostras ambientais, destaca-se a análise por ativação com nêutrons devido à sua alta sensibilidade e rapidez na análise. O objetivo deste trabalho foi validar o método para a determinação de U em amostras de biomonitores de cascas de árvores e bromélias, por meio dos procedimentos de análise instrumental por ativação com nêutrons térmicos (INAA) e análise por ativação com nêutrons epitérmicos (ENAA) ambos com irradiações de curta e longa duração no reator nuclear IEA-R1. Para a validação dos resultados com relação à precisão e à exatidão, foram analisados 11 materiais de referência certificados (MRCs), cujos dados foram avaliados por meio dos valores de Z score e de HorRat. Os procedimentos experimentais consistiram na irradiação térmica e epitérmica de amostras e de padrões de U por períodos de curta e longa duração, seguida de espectrometria de raios gama usando detector de Ge hiperpuro de alta resolução. Os resultados obtidos para a estimativa da incerteza padrão combinada da fração mássica de U, em uma amostra de casca de árvore, mostraram que a fonte de incerteza que mais contribuiu foi a estatística de contagem e o procedimento que apresentou a menor incerteza nos resultados foi a ENAA de longa duração. Os resultados dos MRCs apresentaram, na maioria dos casos, boa precisão e exatidão e as frações mássicas de U determinadas nas cascas de árvores e bromélias apresentaram resultados reprodutíveis. Dentre os quatro procedimentos estudados, a ENAA de longa e curta duração permitiu, em geral, a quantificação de U nas amostras dos materiais analisados. A INAA de longa e de curta duração nem sempre foi efetiva na determinação de U devido ao problema de interferência espectral e do alto valor de limite de detecção. Os limites de detecção determinados pelos procedimentos estudados foram comparados e os menores valores foram obtidos pela ENAA de longa duração. Em virtude dos fatos mencionados, o procedimento mais indicado para a determinação de U nas amostras ambientais analisadas nesse trabalho foi a ENAA de longa duração devido aos seus baixos limites de detecção, boa precisão e exatidão dos resultados e redução do problema de interferência nas análises.
Determination of uranium in tree bark samples by epithermal neutron activation analysis
2017 - LIMA, N.P.; SAIKI, M.
It is well known that uranium is a toxic element to human beings and it is considered as an environmental pollutant. This element presents accumulative property and can be concentrated on the organs causing various types of diseases. Uranium is widely distributed in the environment, so it is of great interest to improve the method of neutron activation analysis to be applied in its determinations in tree barks used as environmental pollution biomonitor. For analytical quality control of the U results, certified reference materials (CRMs) were analyzed. The tree bark samples were collected from the Tipuana tipu (Tipuana) and Poincianella pluviosa (Sibipiruna) species and, for the analyses the outer layer of the bark was grated and then ground to obtain a powder. Aliquots of CRMs or tree bark samples were weighed in polyethylene envelopes and, irradiated together with U synthetic standard, inside a Cd capsule for epithermal neutron activation analysis (ENAA). The irradiation was performed a pneumatic transfer system at the IEA-R1 nuclear research reactor at IPEN - CNEN/SP. The thermal neutron flux used was of 1:9 1012 n cm􀀀2s􀀀1 and the irradiation time was of 60 seconds. After adequate decay time, the sample and U standard were measured using a HGe detector coupled to a digital spectrum analyzer DSA 1000, both from Canberra. Uranium was identified by gamma ray peak of 74.66 keV of 239U and half-life of 23.47 minutes. The concentration of U was calculated by comparative method. A total number of five CRMs were analyzed and its results presented relative standard deviations lower than 13.4%, relative errors lower than 3.1% and |Z score| values lower than 0.29. Results obtained in the analyses of tree barks varied from 81.8 to 222.1 ng/g, indicating that U concentrations in the analyzed samples were very low.
Determination of uranium in tree bark samples by epithermal neutron activation analysis
2017 - LIMA, NICOLE P. de; SAIKI, MITIKO
In this study uranium (U) concentrations were determined in certi ed reference materials (CRMs) and in tree bark samples collected in \Cidade Universit aria Armando de Salles Oliveira" (CUASO) USP, S~ao Paulo. The barks were collected from di erent species namely Poincianella pluviosa and Tipuana tipu. These bark samples were cleaned, dried, grated and milled for the analyses by epithermal neutron activation analysis method (ENAA). This method consists on irradiating samples and U standard in IEAR1 nuclear reactor with thermal neutron ux of 1:9 1012 n cm􀀀2 s􀀀1 during 40 to 60 seconds depending on the samples matrices. The samples and standard were measured by gamma ray spectroscopy. U was identi ed by the peak of 74.66 keV of 239U with half life of 23.47 minutes. Concentration of U was calculated by comparative method. For analytical quality control of U results, certi ed reference materials were analysed. Results obtained for CRMs presented good precision and accuracy, with jZ scorej 0.39. Uranium concentrations in tree barks varied from 83.1 to 627.6 ng g􀀀1 and the relative standard deviations of these results ranged from 1.8 to 10%.