Navegando por Assunto "Estuary"

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Acesso aberto (Open Access)
Caracterização física do estuário do rio Mojuim em São Caetano de Odivelas - PA
(Universidade Federal do Pará, 2015-02-25) ROCHA, Adriano Santos da; ROLLNIC, Marcelo; http://lattes.cnpq.br/6585442266149471
The present study has as objective describe the hydrodynamics, hydrologic and morphological aspects, of estuary of Mojuim River, it is localized in São Caetano de Odivelas city –PA (Salgado Paraense),it is analyzing the variations that happen according sea cycle seasonality (rain regime).The hydrologic and hydrodynamics data was collected in two seasonal period in 2014:March,it corresponds to rainy period (~500 mm)and September, it corresponds to dry period (~100 mm),both during tide of syzygy. The bathymetric survey happened only in the rainy period and it was realized with an echo sounder in a sampling grid with 116 spaced cross profile of 200m.In the estuarine channel,it was defined a section where it was realized profiles of strength measurement and current intensity and output, with ADCP, and in three fixed stations,right bank (RB), center(C),and left bank (LB)it was realized collections of conductivity and turbidity with a CDT and an OBS, in the water column. The pattern of tidal and the salinity they were also obtained with a pressure sensor and conductivity fixed in the LB during 56 days in the rainy period and 57 days in dry ones. The estuarine is shallow (4,5 m of average depth) and it is restrained by a regime of semidiurnal macrotidals. During a tidal cycle the salinity increases in the floods and decreases in the ebb tide in both seasonal periods. Turbidity increases in the floods and it decreases in the ebb tide of the rain period and the value measured in the center (C) is double found in the banks. In the dry period, the salinity was higher to rainy period (average 20 and 8, respectively) .This estuarine presents well mixed; it is vertically homogeneous in the rainy period and highly stratified in the dry. The flood flows occur predominantly at the center section, while the ebb flows predominate in the RB, in the two situations the highest intensity of the current occurs in the rainy season. The estuary is an importer in the two periods, however, more entering in the rainy period (resulting transport of 95,87 m³/s) .These data correspond to the first information on the hydrological and hydrodynamics characteristics of the estuary and they can support further studies in the region.
Acesso aberto (Open Access)
Investigação da influência antrópica na concentração de nutrientes inorgânicos dissolvidos no entorno da cidade de Belém-PA
(Universidade Federal do Pará, 2022-08-30) PORTO, Yuri Paixão Santa Rosa; ROLLNIC, Marcelo; http://lattes.cnpq.br/6585442266149471; https://orcid.org/0000-0002-8601-1514
Water is one of the most important natural resources, especially in the Amazon context. The disorderly population increase and consequent mismanagement of this resource causes worrying environmental changes in terms of its quality. According to the National Sanitation Information System - SNIS, the northern region of the country treats about 22.0% of the sewage generated and in the Metropolitan Region of Belém, below the national average, with 11.3% of sewage collection. The study area encompasses Guajará Bay and adjacent areas such as the Guamá and Acará rivers. Water collections were carried out during the rainy season (May), in 4 sections divided into left bank (ME), middle (M) and right bank (MD) with surface and bottom collections, every 4 hours for 13 hours to analyze the entire tidal cycle. Parameters were analyzed in situ (Temperature, pH, Eh, electrical conductivity, turbidity, OD, %OD and total dissolved solids) and in the laboratory (Silicate, phosphate, nitrate and nitrite), in addition to determining the intensity, speed and direction of the current. with the aid of an ADCP to obtain the flow and calculate the nutrient flow. The study area has some more remote places with little or no human influence throughout its extension, and others with untreated domestic and industrial effluent discharge points. The objective of this work is to investigate a possible anthropic contribution in the flow of dissolved inorganic nutrients from the water bodies that bathe the city of Belém-PA and surroundings. The Guamá River near the “alça viária” showed the lowest values of dissolved inorganic nutrients, unlike the Acará River which, despite its geographical distance from the RMB, showed the highest values of nutrient concentration. The mouth of the Guamá river had higher nutrient values on its right bank and the Guajará bay in its central portion, due to the influence of domestic and industrial waste. The Guamá river near the “alça viária” is relatively preserved, with a low concentration of dissolved inorganic nutrients, increasing only near its mouth, while the Acará presented higher values mainly due to the intense agricultural activity in the surroundings of its basin. The Guajará Bay, despite receiving discharges from the Acará and Guamá rivers, has lower nutrient values than the two locations, demonstrating its capacity for self-purification and dilution.