Radionuclídeos naturais e artificiais em seis perfis de solos do estado do Rio Grande do Sul

Concentrations of natural radioactive series radionuclides, of K-40, and of radioactive fallout Cs-137 are determined. Many physical, chemical and biological parameters influence the radioactivity vertical distribution in soils. Among these factors are soil type and characteristics; rainfall; superficial layers perturbations and other peculiar properties of the soil such as concentration and types of clay mineral, organic matter, etc. High performance gamma-ray spectrometry is used to determine radionuclide concentrations. Ten samples of each type of soil are collected, down to 50 cm with samples collected every 5 cm. pH, clay concentration, organic carbon and K+, Na +, Ca++ and Mg++ cations and total acidity are analyzed, among other parameters. Data on local pluviometry, temperatures and relief, latitude, longitude and altitude are also collected. It is observed that the highest concentrations of Cs-137 are found in the three uppermost superficial samples for every profile. More than 60% of the Cs-137 lays within the 25 cm uppermost layer for all sampling locations. It is observed for soil superficial samples of every profile, a high linear correlation between Cs-137 concentration and organic carbon concentration and that, down to a depth of 50 cm, Ac-228 and TI-208 concentrations do not vary appreciably for different equivalent samples. These results help showing the state of relative equilibrium within the six profiles studied. So it may be observed that these soils have not suffered from erosion and that lixiviation process is not important for these elements which belong to natural radioactive series.Determinou-se as concentrações de radionuclídeos pertencentes ás séries radioativas naturais, do K-40 e do Cs-137, proveniente da precipitação radioativa. Muitos parâmetros físicos, químicos e biológicos influenciam a distribuição vertical da radioatividade dentro dos solos. Estes fatores incluem a natureza e as características do solo; a quantidade de chuva depositada; as perturbações das camadas superficiais; e outras propriedades peculiares do solo, como teores e tipos dos minerais de argila, matéria orgânica, etc. Para as medidas das concentrações de radionuclídeos, utilizou-se a técnica de espectrometria gama de alto desempenho. Foram coletadas 10 amostras de cada tipo de solo, até 50 cm de profundidade, com amostras obtidas de 5 em 5 cm. Foram efetuadas análises que determinam, entre outros parâmetros, pH, teores de argila, carbono orgânico e cátions K+, Na+, Ca++ e Mg++ e acidez extratível. Também foram obtidos dados sobre a precipitação pluviométrica local, temperatura e relevo, e relativos a latitude, longitude e altitude. Observou-se que as maiores concentrações de Cs-137, em Bmq-2, encontram-se nas três amostras mais superficiais de cada perfil. Acima de 60% da concentração está confinada nos 25 centímetros superiores de todos os locais de amostragem. Constatou-se uma elevada correlação linear entre as concentrações de Cs-137, nas amostras superficiais de solos de cada perfil, e o conteúdo de carbono orgânico e, que até os 50cm de profundidade, os teores de Ac-228 e Tl-208, para as diferentes amostras de cada perfil de solo analisado, não variaram substancialmente. Estes dados contribuem para mostrar o estado de relativo equilíbrio radioativo nos seis perfis de solos estudados. Observa-se, assim, que estes solos não sofreram erosão, e que o processo de lixiviação é pouco importante para estes elementos pertencentes ás famílias radioativas naturais

Solar and climate signal records in tree ring width from Chile (AD 1587-1994)

Abstract Tree growth rings represent an important natural record of past climate variations and solar activity effects registered on them. We performed in this study a wavelet analysis of tree ring samples of Pilgerodendron cupressoides species, from Glaciar Pio XI (Lat: 49112 0 S; 74155 0 W; Alt: 25 m), Chile. We obtained an average chronology of about 400 years from these trees. The 11-yr solar cycle was present during the whole period in tree ring data, being more intense during Maunder minimum (1645-1715). The short-term periods, around 2-7 yr, that were found are more likely associated with ENSO effects. Further, we found significant periods around 52 and 80-100 yr. These periodicities are coincident with the fourth harmonic (52 yr) of the Suess cycle (208 yr) and Gleissberg ($80-100 yr) solar cycles. Therefore, the present analysis shows evidence of solar activity effect/modulation on climatic conditions that affect tree ring growth. Although we cannot say with the present analysis if this effect is on local, regional or global climate, these results add evidence to an important role of solar activity over terrestrial climate over the past$400 yr.

Periodicidades, tendências e previsão a partir da análise espectral dinâmica da série dos níveis do rio Paraguai, em Ladário (1900/1995)

Mean values of monthly and annual level of Paraguay River in Ladário County (1900/1995) were studied by several numerical methods which include: Fourier analysis, periodogram, dynamic spectral analysis and iterative regression. This work intended to identify the main characteristics of the river flow and to use the main periodicities embedded in the series to evidence possible causes or factors which may influence its variations. The river flow is not stationary; however, an attempt was done to use only the eight main periods to predict the river behavior at a time scale of a few decades.As séries das médias mensais e anuais dos valores do nível do rio Paraguai, em Ladário (1900/1995), foram estudadas por vários métodos numéricos que incluem: análise de Fourier, periodograma, análise espectral dinâmica e regressão iterativa. A finalidade do trabalho é identificar as grandes características do regime do rio e, através das principais periodicidades embutidas na série, as possíveis causas ou os fatores que podem intervir em suas variações. O regime do rio não é estacionário, porém, tentou-se utilizar apenas as oito periodicidades maiores para prever o comportamento do rio numa escala de tempo de algumas décadas

Predictions of Sea Surface Temperature in Tropical Ocean Using Neural Networks

A review of researches on the relationship between the tropical ocean sea surface temperatures (SST) and rainfalI anomalies in Northeast Brazil was introduced. In this work, two neural network models are implemented to reconstruct and predict the time series of the SST in two regions: the tropical Atlantic ocean (Wrigbt index, from 1854 to 1985) and the tropical Pacific ocean (regions Ninol-2: 0\ub0N-10\ub0S, 270\ub0E- 280\ub0E and Nino 4: 5°N-5°S, 160\ub0E-150\ub0E, from 1950 to 1995). The selected neural networks include Backpropagation Neural Network (BNN) and Time Delay Neural Network (mNN). Both were imple- mented in the neural network stimulator SNNS. For the Wright index, the trained Backpropagation Neural Network successfully predicted the index of the following four months with the relative errors from 1.40 to 3.34%. For SST in Nino 1-2 and Nino4 regions, the Time Delay Neural Network was used for reconstruction and prediction. Comparing with the next six month observations and predictions, alI of them are 10- cated within the predicted error bars. These results show that neural network methods may be used, within certain limits, for prediction and evaluation of predictability of time series measured from phenomena influenced by complex climatic and geophysical processes, like SST.Pages: 23-3

Reconstruction and searching ozone data periodicities in southern Brazil (29ºS, 53ºW) Reconstrução e procura de periodicidades nos dados de ozonio região sul do Brasil (29ºS, 53ºW)

Ozone plays a very important role in the nature due its characteristics as a natural filter of ultraviolet solar radiation. Thus, it is pertinent for the scientific community to understand all natural influence factors involving ozone along with a large time series. In this work, a reconstruction of ozone time series obtained by Brewer spectrophotometer from 1994 to 2008 at the Southern Space Observatory (SSO) - 29ºS, 53ºW - Southern Brazil is presented. TOMS-OMI data were used to follow the days without data, where a coefficient of correlation between TOMS-OMI and Brewer is acceptable around r = 0.89. Besides, wavelet analysis to determine the temporal evolution of the frequencies and the amplitudes was applied. Moreover, wavelet analysis aiming to determine the temporal evolution of the frequencies and the amplitudes was performed. The results pointed a period of 365 days (1 yr) for the seasonal variation of ozone, of 600 days attributed for a possible QBO influence and two periods of 2000 and other 4000 days regarding possibly to the second harmonic of the 11-year solar cycle.O ozônio tem um papel muito importante na natureza devido as suas características como um filtro natural da radiação solar ultravioleta. Portanto, é pertinente para a comunidade científica compreender todos os fatores de influência natural envolvendo ozônio ao longo das séries temporais de grande porte. Neste trabalho, uma reconstrução da série temporal do ozônio obtido pelo espectrofotômetro Brewer 1994-2008 no Observatório Espacial do Sul (29 º S, 53 º W) - Sul do Brasil é apresentado. Os dados do TOMS-OMI foram usados para completar os dias sem dados, onde um coeficiente de correlação entre TOMS-OMI e Brewer é aceitável, em torno de r=0,89. Além disso, foi aplicada a análise de ondeletas para determinar a evolução temporal das frequências e das amplitudes. Os resultados apontam um período de 365 dias (ou 1 ano) para a variação sazonal do ozônio, um período de 600 dias para uma possível influência QBO e dois períodos, um de 2000 e outro de 4.000 dias referentes ao segundo harmônico do ciclo solar de 11 anos e 11 Ciclo de ano solar