Navegando por Assunto "Tapajós"

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Acesso aberto (Open Access)
Distribuição, comportamento e definição de valores de background do mercúrio em sedimentos da bacia hidrográfica do rio Tapajós, Pará, Brasil
(Universidade Federal do Pará, 2023-10-24) RENTE, Augusto de Farias Silva; MARQUES, Eduardo Duarte; http://lattes.cnpq.br/8256609331887637; https://orcid.org/0000-0003-1133-9408; KÜTTER, Vinicius Tavares; http://lattes.cnpq.br/6652786694334612; https://orcid.org/0000-0001-7295-6800
Geochemical mapping and background determination help identify anomalies in the environment and distinguish natural or anthropogenic sources. Mercury (Hg) is a worrying element because it is conservative and can bioaccumulate and biomagnify. In the watershed Tapajós River, miners apply Hg to recover gold, this Hg can be released into the environment together with Hg from the soil, resulting in contaminated areas, associated with forest suppression, exposing the soil to erosion. In the study carried out, 343 samples of river sediments were collected and analyzed by SGB/CPRM in 2005/2006, with a sampling density of 1/135 km². The Hg content in the samples was analyzed by ICP-OES with a hydride generator. Hg values ranged from 0.01 to 4.46 mg.kg-1, and the geochemical background established for the area was 0.48 mg.kg-1, close to the probable effect level, 0.486 mg.kg-1. When classifying the samples by lithology, namely, alkaline granitoids, calcium alkaline granitoids, sedimentary rocks and gneisses and volcanic rocks, the mMAD showed the respective results, 0.69; 10.19; 0.03 and 0.77 mg.kg-1 for the upper thresholds and 0.01, 0.00, 0.02 and 0.00 mg.kg-1 for the lower threshold. The use and occupation classification, namely, Pasture and Forest presented mMAD values of 6.10 and 0.10 mg.kg-1 respectively for the upper thresholds and 0.00 and 0.01 for the lower thresholds. It should be noted that such a calculation for the mining area cannot be carried out due to the significantly low percentage of samples above the lower detection limit of the analytical method, suggesting high concentrations of Hg only in specific samples. The Enrichment Factor (EF) revealed a significant increase in mercury (Hg) in areas with greater human influence in the interpolation maps, identifying iron manganese oxyhydroxides and clay minerals as the main components responsible for Hg adsorption. The Contamination Factor Maps (CF) identified the same areas as contaminated that the FE identified as enriched. The studied region is naturally enriched in Hg in relation to other biomes, due to the following factors: 1° geogenic, associated with rock erosion and the process of tropical weathering, which leads to the formation of duricrust and lateritic soil, causing Hg to accumulate efficiently in the soil; 2° the local anthropic factor, acting on soil degradation, promoting the conversion of forests into pastures and mining areas, remobilizing and dispersing Hg. Considering the scale of approach of this work, a greater impact related to land use change was observed. A more detailed approach is suggested, such as a greater number of samples on a larger cartographic scale to define local impacts.
Acesso aberto (Open Access)
Geologia e Metalogênese do Depósito Au-Ag (Pb-Zn) do Coringa, Sudeste Província Mineral Tapajós, Pará.
(Universidade Federal do Pará, 2020-09-16) GUIMARÃES, Stella Bijos; KLEIN, Evandro Luiz; http://lattes.cnpq.br/0464969547546706; https://orcid.org/0000-0003-4598-9249
The Tapajós Mineral Province (TMP) is located in the south-central portion of the Amazonian Craton and is considered one of the main metallogenic provinces of Brazil. A significant part of the province comprises felsic volcanic and volcanoclastic rocks and granites, which formed predominantly in two intervals, 2.02 to 1.95 Ga and 1.91 to 1.87 Ga, belonging to several stratigraphic and lithodemic units. Fieldwork, petrography, and high-resolution airborne geophysics allowed us to produce a new map at the 1:100,000 scale for the southeastern portion of the TMP, where the gold and silver (Cu-Pb-Zn) Coringa deposit is located. We identified two new geological units: (1) the volcanic and pyroclastic rocks of the Vila Riozinho Formation, previously attributed to the Iriri Group, including a facies defined here of this formation, which comprises a group of rocks with the largest magnetic content in the region (Vila Riozinho Formation - magnetic pyroclastic facies), and (2) the Serra Alkali Feldspar Granite, which intruded into the Vila Riozinho Formation (VRF). These units are the host rocks of Coringa deposit. The FVR rocks represent a magmatic arc with high K calcalkaline to shoshonitic affinities. There are similarities in the patterns of LILE and HFSE and the multielementar diagrams with the granitic rocks from Creporizão Intrusive Suite (CIS). The contemporaneousness between these units reinforce a possible petrogenetic correlation and converge to the hypothesis of similar sources, of probable remelting of arc rocks. Isotopic data revealed similar behavior between VRF, SAFG and Maloquinha Intrusive Suite expose similar behavior and present negative εNd values; however, it indicates rocks derived from enriched sources (ancient crustal rocks). Therefore these units had the same source during tectonic setting and crustal evolution of TMP. It is a transcurrent post-collisional stage that followed the collision of the Cuiú-Cuiú Magmatic Arc related to the Orosian volcano-plutonic event (2033-2005 Ma). Based on available geochronological information these units can be associated with a volcano-plutonic event that occurred in the Orosirian period, at about 1.98 Ga. The Au-Ag (Cu-Pb-Zn) Coringa deposit, occurs essentially in veins and veinlets whose match the regional trend (NNW-SSE). The host rocks are volcanic and pyroclastic rocks of the Magnetic Pyroclastic Facies (MPF) from the Vila Riozinho Formation (ignimbrites, tuffs, and breccia), and the Serra Alkali Feldspar Granite, with a predominance of the supracrustal rocks The hydrothermal processes affected all lithotypes associated with mineralization, producing distal alteration (carbonate-chlorite-epidote), intermediate-proximal alteration (sericite-pyrite) and proximal alteration (chlorite-hematite). The mineralized veins are generally composed of quartz + pyrite + chalcopyrite + galena + sphalerite + electrum + chlorite + sericite. Gold grains occur as inclusions or fractures in pyrite. The fluids presents low salinity, rich in H2O and poor in CO2, with evidence of mixing (magmatic-meteoric), and the presence of adularia and Mn-carbonate are outstanding features of this deposit. All characteristic converge to confirm an intermediate- sulfidation epithermal deposit as a genetic model to Coringa deposit.
Acesso aberto (Open Access)
Impactos socioambientais atuais e de mudanças futuras na hidroclimatologia da bacia do rio Tapajós na Amazônia
(Universidade Federal do Pará, 2023-06-09) SODRÉ, Vânia dos Santos Franco; SOUZA, Everaldo Barreiros de; http://lattes.cnpq.br/6257794694839685; https://orcid.org/0000-0001-6045-0984; LIMA, Aline Maria Meiguins de; http://lattes.cnpq.br/6572852379381594; https://orcid.org/0000-0002-0594-0187
The intensification of land use and land cover has been increasing environmental and climatic problems in the Amazonian sub-basins, especially in the Tapajos River basin, which is important not only for the region, but for the whole country in terms of economic and socio-environmental issues. This research evaluated the increasing pressure imposed on the Tapajos River basin from the unsustainable use of water resources, deforestation on meteorological variables and the future hydroclimatology of the basin for the next 30 and 60 years. On the water issue, significant environmental impacts were observed in the Upper and Middle Tapajos, where unsustainable uses of water resources were identified from the various sectors of the economy, with emphasis on the increase in the number of industries and hydroelectric plants. Conversely, in the Lower Tapajos region there are still significant portions of conserved vegetation cover, which are essential for favoring evapotranspiration and, consequently, cloud formation, but an increase in the unsustainable use of water resources was observed in the region. In the relationship between deforestation and climate, it was noted the existence of correlations between deforestation rates and positive variations in temperature in the Middle Lower Tapajos region. However, no significant variations in precipitation were observed, but there is a slight negative trend (reduction), corroborating the anomaly and trend studies. In the future hydroclimatology, the results showed that the future impacts of climate change on precipitation and elevation measures, both for a more proximate climate (2021-2050) and for a climate at the end of the century (2051-2080), taking into account the moderate and pessimistic scenarios. It was also noted that there will be changes in the frequency of maximum and minimum extremes of precipitation and quota, especially in the regions of the Middle Lower Tapajos, being more sensitive to these changes at the Itaituba station.
Acesso aberto (Open Access)
O rio que embaçou no horizonte: narrativas e percepções sobre os impactos urbanos da construção e operação do terminal da Cargill em Santarém - PA
(Universidade Federal do Pará, 2025-02-27) PIMENTA, Karina Cunha; SILVA, Carlos Freire da; http://lattes.cnpq.br/7489756177996098; https://orcid.org/0000-0002-0202-8678
This study investigates the urban impacts of the installation and operation of the Cargill terminal in Santarém, Pará (Brazil), focusing on the socio-environmental transformations resulting from this intervention and the lived experiences of the city’s residents. The research emerged from an ethnographic approach initiated in 2017, aiming to understand changes in urban landscapes through the narratives of residents who, prior to the terminal’s installation, lived in the former Vera Paz beach area and were displaced to the current Laguinho neighborhood. From this perspective, the study reflects on the effects of the eradication of this leisure and sociability space, expanding the analysis to the economic dynamics of agribusiness, the expansion of soy monoculture, and the impacts of large infrastructure projects. Based on a qualitative methodology, the research employs oral narratives, life histories, interviews, poems, songs, and document analysis to explore how the transformations caused by the Cargill terminal have shaped new forms of sociability and resistance. The dissertation interrogates how processes of economic exploitation reshape urban and environmental dynamics, addressing not only economic consequences but also impacts on the "sensible" (affective, sensory, and symbolic dimensions) and the subjectivities of residents. The study also highlights the reconfiguration of the "sensible," symbolized by the disappearance of the former Vera Paz beach, and how this represents an infringement on the right to the city. It reveals an acceleration of socio-environmental violence, rendered invisible by mainstream media, and proposes an interdisciplinary lens for analyzing urban issues in the Amazon, integrating emotional and cultural dimensions often neglected in such debates. Ultimately, this work aims to pave the way for deeper investigations into Amazonian landscapes and the new forms of struggle and belonging emerging from these socio-environmental conflicts.