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Marcelo Bevilacqua Remor Silvio César Sampaio Sacha de Rijk Marcio Antônio Vilas Boas Jackeline Tatiane Gotardo Everton Tiago Pinto Fábio Augusto Schardong 《国际泥沙研究》2018,33(4):406-414
The objective of this study was to evaluate the concentration and distribution of heavy metals in the sediments of Paulo Gorski Lake, as well as the metals’ bioavailability and potential ecological risk, and to define the anthropogenic and natural heavy metal contributions to the lake. The chemical elements calcium (Ca), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), nickel (Ni), lead (Pb), and zinc (Zn) were quantified by flame atomic absorption spectrophotometry with two extraction methods to quantify the bioavailable and non-bioavailable fractions. The data were evaluated using multivariate statistics and sediment quality indices. All sediment collection points (S1, S2, S3, S4 and S5) are different in terms of the concentration of heavy metals, except for S4 and S5, which were statistically equal. The bioavailable fraction of the elements in the sediment follows the sequence Pb>Cu>Mn>Zn>Ni>Cr>phosphorus (P) for all points. The elements Co, Cr, Pb, and Zn showed moderate to considerable contamination at all points. Only points S3 and S5 had moderate ecological risk. Urbanization has been affecting Paulo Gorski Lake via the input of chemical elements, especially Co and Pb. The points most affected by heavy metal contamination are S3 and S5 when the sedimentological sensitivity factor is considered. The lake has high hydrodynamics, causing some of the contaminants that enter the system to leave it, leading to potential negative impacts downstream. 相似文献
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Marcio Boechat Albernaz Lonneke Roelofs Harm Jan Pierik Maarten G. Kleinhans 《地球表面变化过程与地形》2020,45(15):3824-3841
Natural levees are common features in river, delta and tidal landscapes. They are elevated near-channel morphological features that determine the connection between channel and floodbasin, and consequently affect long-term evolution up to delta-scales. Despite their relevance in shaping fluvial-tidal systems, research on levees is sparse and often limited to fluvial or non-tidal case studies. There is also a general lack of understanding of the role of vegetation in shaping these geomorphic units, and how levee morphology and dimensions vary in the transition from fluvial to coastal environments, where tides are increasingly important. Our goal is to unravel the effects of fluvial-tidal boundary conditions, sediment supply and vegetation on levee characteristics and floodbasin evolution. These conditions were systematically explored by 60 large-scale idealized morphodynamic simulations in Delft3D which self-developed levees over the course of one century. We compared our results to a global levee dataset compilation of natural levee dimensions. We found that levee height is determined by the maximum water level, provided sufficient levee building sediments are available. Discharge fluctuations increased levee width and triggered more levee breaches, i.e. crevasses, that effectively filled the fluvio-tidal floodbasin. The presence of wood-type (sparse) vegetation further increased the number of crevasses in comparison with the non-vegetated scenarios. Conversely, reed-type (dense) vegetation strongly dampened tidal amplitude and reduced the accommodation space and sedimentation further into the floodbasin, resulting in narrower levees, no crevasses and limited floodbasin accretion. However, dense vegetation reduced tidal forces which allowed levee growth further downstream. Ultimately, the levees merged with the coastal barrier, eliminating the floodbasin tides entirely. Our results elucidate the mechanisms by which levee and crevasse formation, and vegetation may fill fluvio-tidal wetlands and affect estuary evolution. This brings new insights for geological reconstructions as well as for the future management of deltas and estuaries under sea-level rise. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd 相似文献
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GPS Solutions - Strong ionospheric electron content gradients may lead to fast and unpredictable fluctuations in the phase and amplitude of the signals from Global Navigation Satellite Systems... 相似文献
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The Barcelona Basic Model (BBM) is an extension of the Cam clay model that has become popular in applications involving unsaturated soils and, in particular, in simulations using the finite element method. Partially saturated soils can be loaded in different ways, for instance, mechanically and/or hydraulically. In addition, cycles of loading and unloading can be applied. The present work introduces a modification of the BBM in order to simplify its computer implementation and also to allow the simulation of elastoplastic behaviour during cycles of both mechanical and hydraulic loading. A unique smooth yield surface is introduced and a two-yield surfaces concept is applied in order to represent the cyclic behaviour. The influence of the intermediate principal stress on the strength is also accounted for. Finally, the numerical integration (stress update) of the extended BBM is briefly discussed. 相似文献
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Large‐scale connectivity of Grapsus grapsus (Decapoda) in the Southwestern Atlantic oceanic islands: integrating genetic and morphometric data 
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下载免费PDF全文 Mariana M. Teschima Patrícia R. Strӧher Carina R. Firkowski Marcio R. Pie Andrea S. Freire 《Marine Ecology》2016,37(6):1360-1372
The degree of connectivity among island populations can influence their demography and affect their level of genetic differentiation. In this study we investigated genetic and morphometric differences among four populations of Grapsus grapsus (Linnaeus 1758), in Saint Peter and Saint Paul Archipelago (0°55′ N, 29°20′ W), Fernando de Noronha Archipelago (3°50′ S, 32°24′ W), Rocas Atoll (3°50′ S, 33°49′ W) and Trindade Island (20°30′ S, 29°20′ W) from 2003 to 2011. Morphometric results indicated the existence of two distinct groups based on the morphology of their chelae (Trindade Island/Saint Peter and Saint Paul Archipelago versus Fernando de Noronha/Rocas Atoll). In addition, genetic variation in a fragment of the mitochondrial control region revealed substantial differentiation between Trindade and the other islands, with Trindade Island showing only exclusive haplotypes. The congruence of the genetic and morphologic analyses suggests the occurrence of a divergent population in Trindade Island as well as high connectivity among the three remaining equatorial islands. This is the first study to assess the level of morphologic differentiation and genetic connectivity of a species among all four Southwestern Atlantic oceanic islands. Our results provide valuable insight into understanding connectivity through surface ocean currents and suggest that the unstable current system of this area could be responsible for different dispersal patterns. We also suggest that the design of Brazilian marine protected areas should be adjusted to provide stronger protection for Trindade Island as it harbors unique genetic and morphologic variation in G. grapsus. 相似文献
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Pedro Walfir M. Souza-Filho Roberto Vizeu L. Pinheiro Francisco R. Costa José Tasso F. Guimarães Prafulla K. Sahoo Marcio S. Silva Cleverson G. Silva 《地球表面变化过程与地形》2020,45(14):3732-3746
This work details the role of fault reactivation in the development of tropical montane lakes by using basin morpho-structural analysis and seismostratigraphic studies. The upland lakes are severely faulted sinkholes, whose faults penetrate the Quaternary sedimentary units. Four main stages are related to the lake formation: (i) an Early Proterozoic tectonic deformation of the rocks along the southern border of the Carajás Structure, where the lake is placed; (ii) differential erosion by – and building of – the formation of the South Carajás Hill; (iii) Fe-rich crust formation by weathering and gravitational collapse faults following the E–W plateau border and the start of Violão Lake formation during the Pliocene–Pleistocene; and (iv) episodic fault-fracture reactivation by gravitational collapse causing pulses of subsidence in the lake and outlining its faulted borders. Dissolution of the lateritic crust and erosion by runoff drainage under wet climate conditions were coeval with fault activities, which allowed the deposition of relatively thick clastic deposits organized in three main seismostratigraphic units associated with major lake-level fluctuations. Initial fault reactivation under low-level water started lacustrine basin development with deposition of prograding fan deltas related to the main drainage. A second fault reactivation by gravitational collapse increased the lake accommodation space and resulted in the deposition of fine-grained sediments from dilute interflows or overflows until 36 000 cal year BP. At about 31 000 cal year BP, rapid decreases in the lake water level under redox conditions at the sediment/water interface allowed widespread siderite formation. A third gravitational collapse episode was responsible for the increase in the lake area and depth and the returning of clastic/organic deposition up to the present. This tropical montane lake can be seen as a representative example for understanding the formation of other upland lakes controlled by fault reactivation. © 2020 John Wiley & Sons, Ltd. 相似文献