Local and remote climatic impacts due to land use degradation in the Amazon “Arc of Deforestation”     

Maria Elisa Siqueira Silva  Gabriel Pereira  Rosmeri Porfírio da Rocha 《Theoretical and Applied Climatology》2016,124(3-4):609-620

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Spatial interpolation of precipitation indexes in Sierra Nevada (Spain): comparing the performance of some interpolation methods     

Paulo Pereira  Marc Oliva  Ieva Misiune 《Theoretical and Applied Climatology》2016,123(3-4):683-691

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Linking shock textures revealed by BSE,CL, and EBSD with U‐Pb data (LA‐ICP‐MS and SIMS) from zircon from the Araguainha impact structure,Brazil     

Natalia Hauser  Wolf Uwe Reimold  Aaron J. Cavosie  Alvaro P. Crsta  Winfried H. Schwarz  Mario Trieloff  Carolinna Da Silva Maia de Souza  Luciana A. Pereira  Eduardo N. Rodrigues  Matthews Brown 《Meteoritics & planetary science》2019,54(10):2286-2311

A silicious impact melt rock from polymict impact breccia of the northern part of the alkali granite core of the Araguainha impact structure, central Brazil, has been investigated. The melt rock is thought to represent a large mass of impact‐generated melt in suevite. In particular, a diverse population of zircon grains, with different impact‐induced microstructures, has been analyzed for U‐Pb isotopic systematics. Backscattered electron and cathodoluminescence images reveal heterogeneous intragrain domains with vesicular, granular, vesicular plus granular, and vesicular plus (presumably) baddeleyite textures, among others. The small likely baddeleyite inclusions are not only preferentially located along grain margins but also occur locally within grain interiors. LA‐ICP‐MS U‐Pb data from different domains yield lower intercept ages of 220, 240, and 260 Ma, a result difficult to reconcile with the previous “best age” estimate for the impact event at 254.7 ± 2.7 Ma. SIMS U‐Pb data, too, show a relatively large range of ages from 245 to 262 Ma. A subset of granular grains that yielded concordant SIMS ages were analyzed for crystallographic orientation by EBSD. Orientation mapping shows that this population consists of approximately micrometer‐sized neoblasts that preserve systematic orientation evidence for the former presence of the high‐pressure polymorph reidite. In one partially granular grain (#36), the neoblasts occur in linear arrays that likely represent former reidite lamellae. Such grains are referred to as FRIGN zircon. The best estimate for the age of the Araguainha impact event from our data set from a previously not analyzed type of impact melt rock is based on concordant SIMS data from FRIGN zircon grains. This age is 251.5 ± 2.9 Ma (2σ, MSWD = 0.45, p = 0.50, n = 4 analyses on three grains), indistinguishable from previous estimates based on zircon and monazite from other impact melt lithologies at Araguainha. Our work provides a new example of how FRIGN zircon can be combined with in situ U‐Pb geochronology to extract an accurate age for an impact event.  相似文献   

The New SCIAMACHY Reference Solar Spectral Irradiance and Its Validation     

T. Hilbig  M. Weber  K. Bramstedt  S. Noël  J. P. Burrows  J. M. Krijger  R. Snel  M. Meftah  L. Damé  S. Bekki  D. Bolsée  N. Pereira  D. Sluse 《Solar physics》2018,293(8):121

This paper describes a new reference solar spectrum retrieved from measurements of the satellite instrument SCIAMACHY in the wavelength region from \(0.24~\upmu\mbox{m}\) to \(2.4~\upmu\mbox{m}\) and its comparison with several other established solar reference spectra. The SCIAMACHY reference spectrum was recorded early in the mission before substantial optical degradation due to the harsh space environment sets in. The radiometric calibration of SCIAMACHY, applied in this study, includes a physical model of the scanner unit. Furthermore, SCIAMACHY’s internal white light source (WLS) is used to correct for on-ground to in-flight changes. The resultant calibrated solar spectrum from SCIAMACHY is in good agreement with several available solar spectral irradiance (SSI) references in the visible spectral range. Strong throughput losses due to detector icing in the near infrared (NIR) are now adequately accounted for. Nevertheless, a deficit with respect to the ATLAS-3 composite and SORCE/SIM SSI is observed in the NIR. However, the SCIAMACHY solar reference spectrum agrees well with the recently re-evaluated SOLAR/SOLSPEC-ISS and recent ground measurements taken at Mauna Loa in the NIR.  相似文献   

Granulometric selectivity in Liza ramado and potential contamination resulting from heavy metal load in feeding areas     

Sílvia Pedro  Vera Canastreiro  Isabel Caçador  Eduarda Pereira  Armando C. Duarte  Pedro Raposo de Almeida 《Estuarine, Coastal and Shelf Science》2008

The stomach contents of thin-lipped grey mullets Liza ramado were analysed in terms of granulometric composition and compared to the sediment of potential feeding areas in the Tagus estuary. Total organic matter (TOM) content and heavy metal content were determined in the surface sediment of three areas and eight trace elements were quantified: Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn. The three sampled areas did not differ in TOM; and the heavy metal content was below Effects Range-Low level for most elements. The mean observed concentrations were present in the following sequence: Zn > Pb > Cr > Cu ≈ Ni > Co > Cd > Hg. Stomach contents granulometric composition provided information about the feeding selectivity of the mullets. Sediment fractions with particle size between 20 and 50 μm are preferred, independently of the fishes' length. Smaller standard length (SL) fishes have a higher positive selection of fine grained sediments than those with a larger SL. Finer fractions usually have higher concentration of heavy metals, which makes younger specimens of the thin-lipped grey mullet potentially more exposed to heavy metal load in the estuary. Metal concentration was not independent from the sampling point, presenting higher values near the margins and the estuary tidal drainage system. This means that during the first period of each tidal cycle, the mullets will feed first on the most contaminated areas, as a consequence of their movement following the rising tide to feed on previously exposed areas.  相似文献   

Least-cost adaptation options for global climate change impacts on the Brazilian electric power system     

Andre Frossard Pereira de Lucena  Roberto Schaeffer  Alexandre Salem Szklo 《Global Environmental Change》2010,20(2):342-350

Global climate change induced by the emission of greenhouse gases may pose challenges to energy security. The vulnerability of energy sources, in particular of renewable sources, to climate change raises the need to identify adaptation measures. This paper applies an integrated resource planning approach to calculate least-cost adaptation measures to a set of projected climate impacts on the Brazilian power sector. The methodology used has the advantage of finding optimal solutions that take into consideration the whole energy chain and the interactions between energy supply and demand. Results point in the direction of an increased installed capacity based, mostly, on natural gas, but also sugarcane bagasse, wind power and coal/nuclear plants, to compensate for a lower reliability of hydroelectric production, amongst other impacts. The indirect effect of these results is the displacement of natural gas from other consuming sectors, such as industry, in favor of its use for power generation. Results obtained are, however, based on the techno-economic premises used in the simulation, which may vary in the long term.  相似文献   

Effect of tidal flooding on metal distribution in pore waters of marsh sediments and its transport to water column (Tagus estuary, Portugal)   总被引：1，自引：0，他引：1  

Juan Santos-Echeandía  Carlos Vale  Miguel Caetano  Patrícia Pereira  Ricardo Prego   《Marine environmental research》2010,70(5):358-367

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Influence of damage on pore size distribution and permeability of rocks     

Chloé Arson  Jean‐Michel Pereira 《国际地质力学数值与分析法杂志》2013,37(8):810-831

The model proposed in this article relates permeability to porosity measurements that can easily be performed in the laboratory. The pore size distribution (PSD) curve is updated with strains and damage. The updated volumetric fractions of natural pores and cracks are introduced in the expression of permeability. Contrary to classical permeability models based on PSD integrations, the model proposed in this article accounts for possible changes in the porosity modes: one mode for undamaged samples and two modes for cracked samples. The proposed approach also accounts for varying states of damage, as opposed to classical fracture network models, in which the cracks pattern is fixed. The only material parameters that are required to describe the microstructure are the lower and upper bounds of the pores size for both natural pores and cracks. All the other PSD parameters involved in the model are related to macroscopic parameters that can easily be determined in the laboratory, such as the initial void ratio. The framework proposed in this article can be used in any damage constitutive model to determine the permeability of a brittle porous medium. Drained triaxial compression tests have been simulated. Before cracks initiation, permeability decreases while the larger natural pores are getting squeezed. After the occurrence of damage, permeability grows due to the increase of cracks density. The model performs well to represent the influence of the confining pressure on damage evolution and permeability variations. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Suitability of GNSS for analysis of soil subsidence in Recife in a highly urbanized coastal area     

de Luna  Rejane Maria Rodrigues  dos Anjos Garnés  Silvio Jacks  da Silva Pereira Cabral  Jaime Joaquim  dos Santos  Sylvana Melo 《Natural Hazards》2021,106(3):1821-1837

Natural Hazards - Recife Metropolitan Region, in the northeast of Brazil, is formed by a coastal plain bounded by hills and by the Atlantic Ocean. Recife Metropolitan Region has about 4 million...  相似文献   

Seasonal fluctuations of tissue mercury contents in the European shore crab Carcinus maenas from low and high contamination areas (Ria de Aveiro, Portugal)     

Pereira E  Abreu SN  Coelho JP  Lopes CB  Pardal MA  Vale C  Duarte AC 《Marine pollution bulletin》2006,52(11):1450-1457

The main objective was to study the seasonal variation of mercury concentrations in different tissues (muscle, hepatopancreas and gills) of Carcinus maenas from low and high Hg contaminated areas, a valuable resource in temperate estuaries and a possible pathway for human uptake. Individuals of two size classes (around 35 and 55 mm cephalothorax wide) were captured monthly between March 1999 and May 2000 in two areas of Ria de Aveiro: in the main navigation channel that connects the lagoon to the sea, and in the inner lagoon area heavily contaminated by mercury (maximum Hg in sediments of 5.4 microg g(-1)). Pronounced decreases in salinity and temperature and reduced food availability in winter seemed to be the responsible for the decline of the crab condition index (0.75-0.45) in larger individuals. Muscle and hepatopancreas exhibited higher mercury concentrations than gills, with concentrations in the contaminated site ranging from 0.03 to 0.63 microg g(-1) and 0.02 to 0.34 microg g(-1), respectively. Linear regressions between muscle and hepatopancreas (r=0.94, p<0.001) and muscle and gills (r=0.97, p<0.001) suggested a rapid redistribution of mercury inside the organism. During winter, a rapid elimination of mercury was found in the three analysed tissues followed by uptake. Larger crabs presented elimination rates from 18 to 34 ng g(-1) per week, while the smaller crabs showed lower elimination rates (10-24 ng g(-1) per week). The uptake was similar in both size classes (11-15 ng g(-1) and 8.1-15 ng g(-1) per week, respectively for large and small crabs). Our results suggest that C. maenas harvested in the contaminated areas must be considered with caution, since Hg concentrations were found to exceed the threshold concentration allowed for human consumption (0.5 microg g(-1)).  相似文献