Navegando por Assunto "Marés"

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Acesso aberto (Open Access)
Análise de alguns parâmetros de qualidade da água na baía do Guajará em Belém-PA e os efeitos do regime pluviométrico e de marés
(Universidade Federal do Pará, 2018-04-27) ARAÚJO, Vívian Evelyne Silva; ROCHA, Edson José Paulino da; http://lattes.cnpq.br/2313369423727020
Belém is located in the estuarine region, conformed by the Guajarino Estuary, which integrates the Marajoara Gulf, whose fluvial environment is formed at the confluence of the rivers Pará, Tocantins, Acará and Guamá (IPEA, 2016). The water level of the Guajarino Estuary presents fluctuations associated with the seasonal effect (seasonal variations of the rain in the hydrological basins) and the tide (variations of the tide level). The elaboration of this study is due to the fact that the seasonal variations seem to be associated to the environmental changes, that occur in the ecosystem, such as the effect of hydrological seasonality - tides and rainfall. The present study will analyze the physico-chemical components of the Guajará Bay water, relating them to the tides and the hydrological dynamics of the Guamá and Pará rivers, also in this research will be made the analysis of the role of precipitation in the alteration of the water bay physicochemical components. Initially, a descriptive statistic was made, verifying the values of the averages, of the maximum and minimum, facilitating to observe which are in agreement with the current resolution of CONAMA 357/2005. It was also applied the statistical method of Pearson correlation to evaluate the degree of relationship between variables, the correlation was first studied between physico-chemical parameters, thus, it was observed that the parameters that have a strong positive correlation were the electrical conductivity, TDS and salinitiy. The other parameters did not presented significative correlation, demonstrating that they were independent of each other. When applying the correlation between the physical-chemical parameters and the rainfall, no positive or negative correlation was found between these variables, meaning that the role of the rainfall city of Belém, was not mostly important in the variation of the physico-chemical components of the bay and this was also the case for the relationship between the parameters and the tide heights. The behavior graphs of the physical-chemical parameters, in relation to rainfall, showed that among the nine parameters analyzed, six parameters were altered, such as: pH, temperature, electrical conductivity, TDS, salinity, OD and Turbidity. These parameters have changed due to precipitation. The results of the parameters regardind the tides were observed among the nine parameters studied, decreasing the temperature, and increasing the values of electrical conductivity, TDS, salinity and turbidity.
Acesso aberto (Open Access)
Dinâmica dos fluxos de dióxido de carbono e metano em área de várzea e terra firme do estuário Amazônico
(Universidade Federal do Pará, 2022-04-29) FLORES ARONI, Mario; JARDIM, Mário Augusto Gonçalves; http://lattes.cnpq.br/9596100367613471; https://orcid.org/0000-0003-1575-1248; CATTANIO, José Henrique; http://lattes.cnpq.br/1518769773387350; https://orcid.org/0000-0001-8335-9593
Terrestrial ecosystems are important for the greenhouse gases exchange (GHG) between the surface and the atmosphere. The objective of this research was to investigate the annual dynamics of carbon dioxide (FCO2) and methane (FCH4) fluxes in different environments, in relation to floristic composition and environmental variables in a floodplain area of the Amazon estuary. The flux of greenhouse gases (GHG) was simultaneously measured in the terrestrial and aquatic environment, in a tidal cycle, during few days in the year. This study also included a seasonal comparison of GHG fluxes in açaí planted in an upland area compared to an açaí managed area in the floodplain of the Amazon estuary. The floodplain study was carried out in the Environmental Protection Area of Combú Island (APA Combú), Belém, Pará (Brazil), between 2019 and 2021. The study in the upland area was carried out in Santa Maria do Pará. The methodology to measure soil and water FCO2 and FCH4 consisted of closed dynamic chamber and floating chambers methodology, respectively. The Amazonian estuaries showed topographic variability reflected in the water table height, which influences the soil FCO2 and FCH4 dynamics. In the same way that increase in soil temperature contributed to CO2 emissions. Therefore, a possible increase in global temperature could favor CO2 fluxes in the Amazon estuary. The tidal influence in the stream has strong impacts on FCO2 and FCH4 of the water, which play a key role in the carbon cycle through the CO2 and CH4 exchange between water-atmosphere environments. Lowland soils dominated by açaí plantations are a source of CO2 and CH4. However, the advance of açaí plantations in upland is positive for the environmental benefit (CH4 sink).
Acesso aberto (Open Access)
Hidrodinâmica, transporte e proveniência sedimentar no baixo rio xingu e sua importância como “Tidal River” amazônico
(Universidade Federal do Pará, 2022-07-14) MEDEIROS FILHO, Lucio Cardoso de; LAFON, Jean Michel; http://lattes.cnpq.br/4507815620234645; ASP NETO, Nils Edvin; http://lattes.cnpq.br/7113886150130994
This research is based on the investigation of the processes (geological and hydrodynamic) that govern the recent evolution of a large tributary of the lower Amazon, the Xingu River. The aim was to investigate its aspects of sedimentary evolution and hydrological flows, from already consolidated data on the filling of its ria and how its patterns of transport and sediment trapping, its seasonal and tidal effects have been established, in addition to understanding the role of the Amazon River as a regulator in the dynamics of its tributary. Hydrodynamic measurements of flow, velocity and water level along with bottom sediment and MPS samples were collected at 3 annual seasons (February, June and November). The results provided support for the investigation of the Xingu-Amazonas interaction and the evolution of the bottom morphology of the lower Xingu. The results suggest a filling of the ria both by the Xingu River, forming a prominent headwater delta, and the Amazon River, where tidal variations transport sediments upstream in the Xingu River. On the other hand, large areas in the central part of the ria indicate muddy sedimentation. Elementar geochemistry allowed us to trace part of the history of sediments and source rocks, together with the analysis of immobile elements (Al, Ti, Zr, Hf, Th) and rare earth elements (REE) because they are poorly fractionated during weathering processes. and they are concentrated in the bottom sediments to the detriment of the dissolved fraction of the rivers. The deposits preserved in the lower Xingu River, despite draining cratonic regions in higher areas, confirm that the bottom material is derived from heterogeneous sources with predominantly intermediate igneous compositions and that they underwent important recycling during fluvial transport. The hydrodynamic modeling allowed to indicate the fluvial discharge as the most relevant forcing for the muddy deposition dynamics in the Xingu estuary. From a numerical model, it was possible to extrapolate the flow and transport dynamics beyond the open boundaries, that is, the central portion of the ria, elucidating the interaction mechanism between river and tidal discharge and the associated sedimentary dynamics. The determination of the amplitudes and phases of the tidal components, whether of purely astronomical origin or resulting from shallow waters, as well as the average level and the hourly discharge proved to be fundamental for the understanding of the governing processes.
Acesso aberto (Open Access)
The dynamics of a frictionally-dominated Amazonian estuary
(2012-09) ASP NETO, Nils Edvin; SCHETTINI, Carlos Augusto França; SIEGLE, Eduardo; SILVA, Marcio Sousa da; BRITO, Roney Nonato Reis de
A hidrodinâmica, morfologia e sedimentologia do estuário do Taperaçu foram investigadas. Este é um entre vários estuários do litoral amazônico que integram a maior extensão contínua de manguezais do mundo, apresentando uma descarga de água doce muito reduzida, atípica para a região. Os resultados revelam grandes bancos arenosos que ocupam em grande parte a porção central do estuário. Areias muito finas e bem selecionadas de origem marinha prevalecem. Fases de enchente mais curtas, com velocidades de corrente substancialmente mais altas, são observadas na porção superior do estuário, como esperado para um estuário raso e dominado por fricção. Por outro lado, uma vazante mais intensa poderia ocorrer como resultado de grandes áreas de manguezais associadas e intenso preenchimento estuarino, sendo que ambas as condições são observadas no Taperaçu. Neste caso, a prevalência da enchente parece estar associada à ausência de uma descarga fluvial efetiva. Além disso, alguns canais de maré conectam o Taperaçu com seu vizinho estuário do Caeté, o que contribuiria para o domínio de enchente. Como um todo, os resultados demonstram uma complexa interação de aspectos de configuração (fricção, drenagem fluvial, conexões com estuários vizinhos, preenchimento e grandes áreas intermareais) na determinação dos padrões hidrodinâmicos, contribuindo para o entendimento dos estuários da região amazônica.
Acesso aberto (Open Access)
The influence of tidal and rainfall cycles on intertidal nematodes: a case study in a tropical sandy beach
(2014-12) VENEKEY, Virág; SANTOS, Paulo Jorge Parreira dos; GENEVOIS, Verônica Gomes da Fonseca
The present study describes the nematode assemblage of the bay of Tamandaré (Brazil), a tropical sandy beach, during the low, flood, high and ebb tides of two consecutive tidal cycles in four different months of the year (May, July, September and November). The nematode assemblage was dominated by Metachromadora and Perepsilonema and varied significantly between months and tides. Densities were lower in July, and changes in assemblage structure occurred during the transitional periods between rainy and dry months, which showed the influence of rainfall. Flood and ebb tides appeared to exercise the greatest influences over the tidal cycle, although the patterns were not very clear. Identification at genera/species level is recommended for future studies, to better understand the patterns of nematode assemblages during tidal cycles.
Acesso aberto (Open Access)
Tide distortion and attenuation in an Amazonian tidal river
(2012-12) FREITAS, Paulo Tadeu Amorim; SILVEIRA, Odete Fátima Machado da; ASP NETO, Nils Edvin
The present study seeks to evaluate tidal propagation in the Guamá-Capim river system, in the Amazonian region, considering hydrodynamic and geomorphological aspects. Available data sets on fluvial discharge and water level variations were considered, besides several methods of measuring the tides (currents, water levels and discharges) recorded at different stations and in different periods. The main point argued is that fluvial discharge is the key-factor in tidal distortion and tidal bore formation in the system investigated, whereas the low relief of the area would be the main factor contributing to landward tidal incursion. The results show an impressive upward tidal incursion of more than 200 km, including substantial distortion -increasing upstream -of the tidal wave, of which the ebb phase lasts up to 5 hours longer than the flood, including higher flood current velocities as far as 161 km upstream. Generally, only hyposynchronous tidal response was observed. Seasonally, the fluvial discharge varies about 10 times in the Guamá and 4 times in the Capim River. The increase of the fluvial discharge results in an increasing distortion of the tide, besides a weak increase of the attenuation. During high fluvial discharge periods in conjunction with equinoctial tides (e.g. March-April), a tidal bore occurs in the system, also increased by the generally low relief. Therefore, the conclusions include: low relief and the distortion related to high fluvial discharges are the main factors controlling tidal propagation along the system and tidal bore formation. Furthermore, the system could be classified as a tidal river, in which massive regional fresh water input results in virtually non-existent salinity throughout the Guamá-Capim system.