S.R. Paulo

Energy balance and canopy conductance of a tropical semi-deciduous forest of the southern Amazon Basin

[1]xa0Deforestation and climate change have the capacity to alter rainfall regimes, water availability, and surface-atmosphere flux of water and energy of tropical forests, especially in ecotonal, semi-deciduous tropical forests of the southern Amazon Basin, which have experienced rapid regional warming and deforestation over the last three decades. To reduce uncertainty regarding current and future energy and water flux, micrometeorological measurements of latent (Qe) and sensible heat flux (Qh) and canopy conductance (Gc) were combined with measurements of sap flux density (Fd) and maximum leaf conductance (gsmax) to characterize the seasonal controls on mass (H2O) and energy exchange of an ecotonal, semi-deciduous forest in northern Mato Grosso, Brazil over the 2005-2006 annual cycle. Average diel patterns and daily rates of energy flux and conductance declined during the dry season; however, the decline in Fd and Qe was smaller and/or more gradual than Gc and gsmax. Weekly averages of transpiration calculated from sap flow measurements during the dry-wet season transition period were positively correlated (r2 = 0.47; p < 0.05; n = 11) with estimates of leaf area index (LAI) derived from the Modis-Aqua satellite platform while estimates of evapotranspiration ET derived from eddy covariance were not, presumably because these estimates also include an evaporation component. Overall, our results suggest that access to deep water reserves can support high rates of Fd and Qe during the dry season, but because of high evaporative demand, declines in plant water potential lead to a corresponding decline in Gc. Furthermore, seasonal variations in LAI, that are likely to be controlled in part by plant water status and phenology, constrain tree and stand transpiration. Thus the consistency of Qe over the annual cycle appears to be the result of trade-offs between water availability (rainfall, soil moisture, water potential), canopy structural properties (LAI), and meteorological conditions including vapor pressure deficit and net radiation.

Recognition of Cretaceous, Paleocene, and Neogene tectonic reactivation through apatite fission-track analysis in Precambrian areas of southeast Brazil: association with the opening of the south Atlantic Ocean

Abstract Apatite fission-track analysis was used for the determination of thermal histories and ages in Precambrian areas of southeast Brazil. Together with geological and geomorphologic information, these ages enable us to quantify the thermal histories and timing of Mesozoic and Cenozoic epirogenic and tectonic processes. The collected samples are from different geomorphologic blocks: the high Mantiqueira mountain range (HMMR) with altitude above 1000xa0m, the low Mantiqueira mountain range (LMMR) under 1000xa0m, the Serra do Mar mountain range (SMMR), the Jundiai and Atlantic Plateaus, and the coastline, all of which have distinct thermal histories. During the Aptian (∼120xa0Ma), there was an uplift of the HMMR, coincident with opening of the south Atlantic Ocean. Its thermal history indicates heating (from ∼60 to ∼80xa0°C) until the Paleocene, when rocks currently exposed in the LMMR reached temperatures of ∼100xa0°C. In this period, the Serra do Mar rift system and the Japi erosion surface were formed. The relief records the latter. During the Late Cretaceous, the SMMR was uplifted and probably linked to its origin; in the Tertiary, it experienced heating from ∼60 to ∼90xa0°C, then cooling that extends to the present. The SMMR, LMMR, and HMMR were reactivated mainly in the Paleocene, and the coastline during the Paleogene. These processes are reflected in the sedimentary sequences and discordances of the interior and continental margin basins.

Indoor radon and radon daughters survey at Campinas-Brazil using CR-39: First results

The first results of a radon and radon daughters (RD) survey performed at Campinas-SP, Brazil, are presented. We employed a technique that, potentially, makes possible to measure the radon and RD activity in the air and to separate from this result the activity of radon, alone. In this preliminary paper only the former activity is studied.

Effects of environmental conditions on the radon daughters spatial distribution

Abstract The influence of environmental conditions on the indoor radon daughters spatial distribution is studied both theoretically and experimentally. Simple theoretical calculations indicate that ventilation and variation in the size distribution of aerosols should play an important role influencing the spatial distribution of indoor radon decay products, but experimental results indicate that these environmental factors have little influence on the spatial distribution of radon daughters near the walls of indoor environments. We have observed that the maximum effective range of the plate-out effect varies only between 1 and 3 cm in typical dwellings.

A possibility of monitoring indoor radon daughters by using CR-39 as an alpha-spectrometer

Abstract Alpha-spectroscopy using CR-39 has been employed by us in monitoring radon and its daughters. By means of measuring the track diameters (considering only the tracks whose ratio between the major and the minor diameters is ≤ 1.100), one can find the energy distribution of the incident α-particles and, in this way, obtaine information about the plate-out rate of radon daughters on material surfaces and also about the concentration of radon and daughters present in the air. In this work, it is shown how radon and daughters monitoring can be improved by using this technique.

Simulating radon daughters diffusion through the air and their depletion on material surfaces

In recent decades, much has been learned about the nature of radon and radon daughters (RD) contamination. Nevertheless, the RD plate-out phenomenon is still not well understood due to environmental conditions, mathematical and detection limitations. When nuclear track detectors are employed to assess the radiation levels of alpha activity, a problem takes place: the self-plate-out effect caused by the detectors surface disturbs the spatial distribution of the surrounding RD and the activity measured is not the real activity present in the air. In this work, we simulate the RD diffusion inside a region where a detector, with shape and size chosen, is exposed. The influence of the detectors size and shape on the RD spatial distribution and on the depletion rate is shown to be in accordance with experimental data.

A discussion of the reliability of alpha-spectroscopy using CR-39 and an image processor

Abstract In this work, experiment results indicating that CR-39 can be employed as along-term alpha-scpectrometer are shown. Tracks due to alpha-particles reaching the detector at angles close to the normal of its surface and having known energies were produced by means of exposing CR-39 sheets to thin films of uranium and thorium placed at convenient distances. These tracks were analysed by using an automated system. Both the area of the tracks and thier mean optical intensity were measured. Our results indicate these two parameters can be used in order to obtain information about the alpha-particle energy (E). The reliability of the use of CR-39 as an α-spectrometer as well as its employment in radon daughters dosimetry are discussed.

Utilização da análise de FOURIER no estudo de variáveis micrometeorológicas de uma floresta de transição do norte de Mato Grosso

In this work, we employed data collected in a transition forest, on the Maracai farm, northwest of Sinop, MT, Brazil. The data was obtained by the eddy covariance method, using equipment installed on a 42m high tower. Its main purpose was to study the potentialities of Fourier analysis applied to data of latent (H) and sensible (Le) heat flux and the air temperature (T). We investigated the main frequencies presented by the data, and obtained mean values for the variables corresponding to every 3 hours, between 1999 and 2005. The main periods obtained with the Fourier method were 24; 12; 4 and 3.4 hours. The first two are attributed to the solar radiation and to the Earth rotation. The last two periods, as indicated by the data, are related to stomata dynamics. In this way, the results indicate that the main factors that predominantly influence the microclimatological variables during the day (frequencies between 10-5 a 10-4 Hz), were the solar radiation and the stomata dynamics. These results reinforce the importance of employing the Fourier method in studying microclimatic dynamics of ecosystems.

Análise de Espectro Singular e Wavelet sobre Série Temporal de Profundidade Ótica de Aerossóis no Pantanal do Brasil

As variacoes das propriedades oticas dos aerossois podem interferir nos processos de transferencia de energia entre a atmosfera e a superficie terrestre. A AOD (Aerosol Optical Depth) e a variavel mais usada para este proposito, a qual possibilita obtencao das principais tendencias e periodicidades das variacoes. Este trabalho objetivou verificar a habilidade das tecnicas SSA (Singular Spectrum Analysis) e Wavelet em descrever as flutuacoes, e respectivas periodicidades, presentes em uma serie temporal de 12 anos (2003-2014) de AOD na faixa do espectro de 550 nm (AOD 550 nm) sobre a regiao do Pantanal brasileiro. Os dados de AOD 550 nm foram adquiridos dos produtos do sensor MODIS, a bordo dos satelites TERRA e AQUA, e foram submetidos a analise de SSA, permitindo a descricao das principais periodicidades da AOD 550 nm, alem de constatar dois periodos dominantes, 1 e 0,5 ano, tendo pequenas variacoes. A Wavelet de Morlet inferiu as periodicidades estatisticamente significativas, entre as quais tambem foram detectadas periodicidades anual e semestral. Ambas as tecnicas reproduziram as principais oscilacoes dos valores da AOD 550 nm, bem como a gradativa reducao dos valores de AOD 550 nm a partir de 2011. A Wavelet possibilitou a interpretacao e visualizacao das principais periodicidades ao longo do tempo, sendo possivel verificar em quais instantes as periodicidades ocorreram.

ESTIMATIVA SAZONAL DA EMISSIVIDADE ATMOSFÉRICA ATRAVÉS DA EQUAÇÃO DE BRUTSAERT NO NORTE DO PANTANAL MATO-GROSSENSE

Nos ultimos anos, tem-se intensificado as pesquisas ambientais na regiao do Pantanal a fim de se conhecer o comportamento micrometeorologico da regiao. No presente trabalho buscou-se verificar se a equacao de Brutsaert pode ser utilizada para a estimativa da emissividade atmosferica na regiao do pantanal Mato-grossense, considerando dois periodos sazonais, sendo um chuvoso e um seco, tendo como base para comparacao os dados obtidos na estacao micrometeorologica aplicados na equacao do balanco de energia, a fim de que possa contribuir para as pesquisas destinadas ao estudo das trocas de energia entre a superficie e a atmosfera da regiao pantaneira. Os resultados obtidos mostraram-se consistentes para o metodo utilizado, pois os valores estimados pela equacao de Brutsaert aproximaram-se significativamente dos valores obtidos atraves da equacao do balanco de energia que utilizou dados coletados no local para os dois periodos estudados. Palavras–chave: Equacao de Brutsaert, periodos sazonais, balanco de energia, Pantanal