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111.
112.
Luiz Carlos Cotovicz Junior Eunice da Costa Machado Nilva Brandini Rafaela Cristine Zem Bastiaan Adriaan Knoppers 《Environmental Earth Sciences》2014,72(2):373-386
This study addresses the distribution of total phosphorus (TP) and its inorganic (IP) and organic (OP) fractions, grain-size and organic matter of surface and recent sediments, coupled to the behavior of total and dissolved inorganic phosphorus (TP and DIP) of the water column, of the semi-pristine Guaratuba Bay estuary, SE Brazil. Surface sediment samples were taken at 43 sites spread along the estuarine gradient and recent sediments from 3 short (35 cm long) cores from the upper, central and lower portions of the estuary, respectively. Highest TP and IP concentrations of surface sediments were detected within the upper sector and the transition zone between the upper and central sectors, all characterized by fine sediments, low salinities and water depths. In contrast, the lower sector and its narrow and deep tidal channel, subject to more intense tidal forcing, exhibited a higher fraction of sandy sediments with lower TP, IP and OP contents. In spite of the spatial variability in sediment grain size, IP corresponded to the major fraction of TP in all estuarine sectors and both TP and IP correlated significantly with the fine sedimentary (silt + clay) grain-size fraction. The fine surface sediments acted as a trap for IP at the fresh water–low salinity interface, which also corresponded to the region of a DIP sink in surface waters. In general, the short sediment cores showed that TP and IP contents increased from 15 cm depths to the top layer. Published sedimentation rates from additional cores taken at the sites of the short cores of this study, implied that depositional alterations of TP and IP increased during the early 1970s, which corresponded to the onset of anthropogenic disturbances from crop plantations in the lowland plains of the river end-member and urbanization at the estuary’s mouth and along the adjacent coast. 相似文献
113.
Marianne Negrini Holger Stunitz Alfons Berger Luiz F. G. Morales 《Contributions to Mineralogy and Petrology》2014,167(3):1-22
We performed high strain (up to 47 %) axial compression experiments on natural quartz single crystals with added rutile powder (TiO2) and ~0.2 wt% H2O to investigate the effects of deformation on the titanium-in-quartz (TitaniQ) geothermobarometer. One of the objectives was to study the relationships between different deformation mechanisms and incorporation of Ti into recrystallized quartz grains. Experiments were performed in a Griggs-type solid-medium deformation apparatus at confining pressures of 1.0–1.5 GPa and temperatures of 800–1,000 °C, at constant strain rates of 1 × 10?6 or 1 × 10?7 s?1. Mobility of Ti in the fluid phase and saturation of rutile at grain boundaries during the deformation experiments are indicated by precipitation of secondary rutile in cracks and along the grain boundaries of newly recrystallized quartz grains. Microstructural analysis by light and scanning electron microscopy (the latter including electron backscatter diffraction mapping of grain misorientations) shows that the strongly deformed quartz single crystals contain a wide variety of deformation microstructures and shows evidence for subgrain rotation (SGR) and grain boundary migration recrystallization (GBMR). In addition, substantial grain growth occurred in annealing experiments after deformation. The GBMR and grain growth are evidence of moving grain boundaries, a microstructure favored by high temperatures. Electron microprobe analysis shows no significant increase in Ti content in recrystallized quartz grains formed by SGR or by GBMR, nor in grains grown by annealing. This result indicates that neither SGR nor moving grain boundaries during GBMR and grain growth are adequate processes to facilitate re-equilibration of the Ti content in experimentally deformed quartz crystals at the investigated conditions. More generally, our results suggest that exchange of Ti in quartz at low H2O contents (which may be realistic for natural deformation conditions) is still not fully understood. Thus, the application of the TitaniQ geothermobarometer to deformed metamorphic rocks at low fluid contents may not be as straightforward as previously thought and requires further research. 相似文献
114.
It is important to understand the Solimões River seasonal hydrological cycle and its dynamics to support systematic environmental monitoring efforts in the Amazon region. These are essential to the contingency response to possible accidents in the existing oil transportation network. This study seeks to map the environmental sensitivity to oil spills in the surroundings of Coari city, Amazonas State (AM). A computational method was employed representing the seasonal inundation phenomenon fluctuations, together with data from the Digital Elevation Model generated by the Shuttle Radar Topography Mission. These were matched with Coari fluviometric time series information and a Japanese Earth Resources Satellite-1 (JERS-1 SAR) geo-referenced mosaic of the Global Rain Forest Mapping Project. In this context, a mathematical morphology technique (watershed) integrated with all aforementioned data applying MatLab and ArcGIS computing resources generated results that enabled a better spatio-temporal understanding of the Amazon seasonal dynamics. Thus, the principal product of the research was the Coari fluvial oil spill sensitivity index map based on segmented inundation levels obtained with the proposed methodology. 相似文献
115.
Caetano Luiz Beber Rafael da Rosa Couto Paulo Emílio Lovato Jean-Philippe Guillemin Bernard Nicolardot Ricardo Bergamo Schenato Jucinei José Comin 《Environmental Earth Sciences》2018,77(14):532
The green revolution laid the foundations of modern agriculture, by using science and technology to produce more from same resources. The pesticides contributed to agricultural output in the last decades; however, their use has resulted in environmental pollution, health problems, soil and water contamination and negative impact on biota. The impacts of agricultural activities to the environment depended on the practices adopted during the production process. Measurement tools to assess the impacts of those practices are necessary to improve agricultural systems and must be evaluated in different ecosystems. Different soils, climates and crops impose many phytosanitary arrangements. This complex network and the fact that most of the indicators and measurement tools are developed for temperate climates makes it difficult to quantify the environmental impacts under subtropical regions. The I-Phy index is a predictive indicator that assesses the risks of pesticide usage in agriculture and identifies as to which practices generate the main environmental impacts of pesticides. The objective of this study was to test the suitability of the I-Phy index for subtropical conditions and, if suitable, compare the pesticide risk between two regions. Five crops were assessed under three different cropping systems: no-tillage, minimal tillage and conventional tillage. The I-Phy index was sensitive in both regions and capable of identifying that no-tillage generally presented risks of environmental pollution slightly lower than the other tillage systems. The results of I-Phy index showed that high environmental vulnerability of the fields and the numerous applications of active ingredients with high risks resulted in high risks of general contamination. The application of I-Phy on these two case studies showed the indicator can be useful as a support tool to farmers, research and extension institutions pursuing management practices with lower impact on the environment. 相似文献
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118.
Paula Garcia Carvalho do Amaral Paulo César Fonseca Giannini Florence Sylvestre Luiz Carlos Ruiz Pessenda 《第四纪科学杂志》2012,27(2):181-191
This paper provides a paleoenvironmental reconstruction of a Late Quaternary lagoon system in the Jaguaruna region of Santa Catarina state, southern Brazil. Integrated results of bulk sedimentary organic matter characterization (δ13C, δ15N and C/N), microfossil (pollen and diatom) and grain‐size analysis from three shallow cores (~2.5 m depth) allowed us to propose an evolving paleogeographic scenario in this coastal region for the last ca. 5500 cal a BP. The lagoonal system in this area was more extensive during the mid‐Holocene than today, with a gradual and continuous lagoon–sea disconnection until the present. We add to the debate regarding relative sea‐level (RSL) variations for the Brazilian coast during the Holocene and discuss the importance of sedimentary dynamics for interpreting changes in coastal ecosystems. The multi‐proxy analysis suggests that changes in coastal ecosystems could be directly related to local sedimentary processes, which are not necessarily linked to RSL fluctuations and/or to climatic variations. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
119.
We consider astronomical and geophysical bounds in order to test Kaluza-Klein like models and some particular models of Bekenstein's
theory. Bounds on the free parameteres of the theories are obtained.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
120.
Adi Nusser Luiz N. da Costa Enzo Branchini Mariangela Bernardi M.V. Alonso Gary Wegner C. N. A. Willmer P. S. Pellegrini 《Monthly notices of the Royal Astronomical Society》2001,320(3):L21-L24
We present a comparison between the peculiar velocity field measured from the ENEAR all-sky D n – σ catalogue and that derived from the galaxy distribution of the IRAS Point Source Catalog Redshift Survey (PSC z ). The analysis is based on a modal expansion of these data in redshift space by means of spherical harmonics and Bessel functions. The effective smoothing scale of the expansion is almost linear with redshift reaching 1500 km s−1 at 3000 km s−1 . The general flow patterns in the filtered ENEAR and PSC z velocity fields agree well within 6000 km s−1 , assuming a linear biasing relation between the mass and the PSC z galaxies. The comparison allows us to determine the parameter where Ω is the cosmological density parameter and b is the linear biasing factor. A likelihood analysis of the ENEAR and PSC z modes yields in good agreement with values obtained from Tully–Fisher surveys. 相似文献