Browsing by Author "da Silva, Marcio Sousa"

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Landscape and Climate Changes in Southeastern Amazonia from Quaternary Records of Upland Lakes
(MDPI, 2023-03-27T00:00:00) Guimar�es, Jos� Tasso Felix; Sahoo, Prafulla Kumar; e Souza-Filho, Pedro Walfir Martins; da Silva, Marcio Sousa; Rodrigues, Tarc�sio Magevski; da Silva, Edilson Freitas; Reis, Luiza Santos; de Figueiredo, Mariana Maha Jana Costa; Lopes, Karen da Silva; Moraes, Aline Mamede; Leite, Alessandro Sab�; da Silva J�nior, Renato Oliveira; Salom�o, Gabriel Negreiros; Dall�Agnol, Roberto
The upland lakes (ULs) in Caraj�s, southeastern Amazonia, have been extensively studied with respect to their high-resolution structural geology, geomorphology, stratigraphy, multielement and isotope geochemistry, palynology and limnology. These studies have generated large multiproxy datasets, which were integrated in this review to explain the formation and evolution of the ULs. These ULs evolved during the Pliocene�Pleistocene periods through several episodes of a subsidence of the lateritic crust (canga) promoted by fault reactivation. The resulting ULs were filled under wet/dry and warm/cool paleoclimatic conditions during the Pleistocene period. The multielement geochemical signature indicates that the detrital sediments of these ULs were predominantly derived from weathered canga and ferruginous soils, while the sedimentary organic matter came from autochthonous (siliceous sponge spicules, algae, macrophytes) and allochthonous (C3/C4 canga and forest plants and freshwater dissolved organic carbon) sources. Modern pollen rain suggests that even small ULs can record both the influence of canga vegetation and forest signals; thus, they can serve as reliable sites to provide a record of vegetation history. The integrated data from the sedimentary cores indicate that the active ULs have never dried up during the last 50 ka cal BP. However, subaerial exposure occurred in filled ULs, such as the Tarzan mountain range during the Last Glacial Maximum (LGM) and the Boca�na and S11 mountain ranges in the mid-Holocene period, due to the drier conditions. Considering the organic proxies, the expansion of C4 plants has been observed in the S11 and Tarzan ULs during dry events. Extensive precipitation of siderite in UL deposits during the LGM indicated drier paleoenvironmental conditions, interrupting the predominantly wet conditions. However, there is no evidence of widespread forest replacement by savanna in the Caraj�s plateau of southeastern Amazonia during the late Pleistocene and Holocene. � 2023 by the authors.
Methodological approach and general guidelines to geochemical mapping and background-baseline analysis for environmental assessment: a case study in the Caraj�s Mineral Province, Brazil
(Sociedade Brasileira de Geologia, 2023-01-09T00:00:00) Souza-Filho, Pedro Walfir Martins; Sahoo, Prafulla Kumar; da Silva, Marcio Sousa; Dall�Agnol, Roberto; Filho, Carlos Augusto Medeiros; Leite, Alessandro Sab�; da Silva Ferreira J�nior, Jair; da Rocha Nascimento, Wilson; da Silva e Silva, G�ssica; Salom�o, Gabriel Negreiros; Sarracini, Fabiana; Junior, Renato Oliveira Silva; da Costa, Marlene Furtado
We present this manuscript as a methodological approach and general guidelines for geochemical mapping and background/baseline projects for environmental assessment in tropical areas. A case study was carried out in the Itacai�nas River watershed (IRW), Eastern Amazon, to fill in a gap in knowledge on the distribution of chemical elements, particularly those potentially toxic, in the near-surface environment of the area. The high-impact results of this research project revealed the need for similar scientific investigation across the globe with the implementation of a systematic methodology. The study shows, for example, the importance of well-planned field activities, multi-medium sampling, analytical methods, laboratory procedures, database construction, and general aspects of data processing and statistical treatment. The importance of this contribution is that it can be used as a reference in support of geospatial analysis in research within the scope of geochemical mapping and background-baseline projects. The database is accessible through a web-based geographic information system front-end; a Geochemical Atlas of the IRW will be available as soon as possible. � 2022 The authors.
Soil-sediment linkage and trace element contamination in forested/deforested areas of the Itacai�nas River Watershed, Brazil: To what extent land-use change plays a role?
(Elsevier B.V., 2022-03-08T00:00:00) Dall'Agnol, Roberto; Sahoo, Prafulla Kumar; Salom�o, Gabriel Negreiros; de Ara�jo, Alessandra Danieli Miranda; da Silva, Marcio Sousa; Powell, Mike A.; Junior, Jair Ferreira; Ramos, Silvio Junio; Martins, Gabriel Caixeta; da Costa, Marlene Furtado; Guilherme, Luiz Roberto Guimar�es
Trace elements (TE) contamination in forested areas of the Itacai�nas River Watershed (IRW), Brazilian Amazon, arouses growing interest owing to the rapid deforestation and mining activities. In this study, soils (surface, SS; bottom, BS) and stream sediments (SD) from forested/deforested areas of IRW were analyzed with the aim of (1) evaluating the major sources of TE (mainly As, Ba, Cd, Cu, Co, Cr, Hg, Mo, Mn, Ni, Pb, V, and Zn), and (2) examining the soil-sediment TE link related to land-use change and/or geologic factors. Compositional data analysis (CoDA) was used to eliminate data closure issues and the centred log-ratio (clr) transformation yielded better results in Principal Component Analysis (PCA). The TE distribution pattern was significantly different (p < 0.05) between forested and deforested areas, but in both areas the TE distribution pattern is significantly correlated between SS, BS, and SD, indicating a strong lithogenic control. PCA (clr-transformed) identified the major geochemical bedrock signature as Fe-Ti-V-Cu-Cr-Ni, which is nearly similar in soil and sediments. The more accentuated enrichment and the maximum number of anomalies of these elements were found in the Caraj�s Basin and are highly coincident with mineral deposits/local lithologies without clear indication of anthropogenic contamination from point sources. Besides geogenic factors, deforestation is also affecting TE distribution in the basin. In deforested areas, Mn was significantly enriched in the surface horizon. Furthermore, linear regression analysis shows stronger TE relationships between soils and sediments in deforested areas than in forested ones, reflecting higher erosion in the former. This could be the reason for the relatively higher enrichment of TE (e.g., Fe, Mn, Cu, Cr, Ni) in deforested sediments. The TE contamination using regional background values provides more accurate results than worldwide reference values. Thus, the former should be considered for a more realistic environmental risk assessment in IRW and other forest ecosystems in the Brazilian Amazon. � 2022 Elsevier B.V.