Environmental Science And Technology - Research Publications

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Browsing Environmental Science And Technology - Research Publications by Author "Ang�lica, R�mulo Sim�es"

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    Changes in the surface water quality of a tropical watershed in the southeastern amazon due to the environmental impacts of artisanal mining
    (Elsevier Ltd, 2023-04-12T00:00:00) Salom�o, Gabriel Negreiros; Dall'Agnol, Roberto; Sahoo, Prafulla Kumar; Almeida, Gabriel Soares de; Amarante, Rafael Tarantino; Zeferino, Leiliane Bozzi; Lopes, Jo�o Paulo Nobre; Souza Filho, Pedro Walfir Martins e; Costa, Normara Yane Mar da; Guimar�es, Jos� Tasso Felix; Silva, Marcio Sousa da; Martins, Gabriel Caixeta; Teixeira, Mayara Fraeda Barbosa; Marques, Eduardo Duarte; Ang�lica, R�mulo Sim�es; Ara�jo, Wilker Emmanoel Oliveira
    The expansion of areas of human occupation and the increase in economic activity and deforestation are negatively impacting the Amazon ecosystem. Situated in the Caraj�s Mineral Province in the southeastern Amazon, the Itacai�nas River Watershed (IRW) encompasses several active mines and has a historical record of intense deforestation primarily linked with the expansion of pasturelands, but also of urban areas, and mining activities. Industrial mining projects are subjected to strict environmental control, but artisanal mining (ASM; �garimpos�) sites have not been controlled, despite their known environmental impacts. In recent years, the opening and expansion of ASM in the IRW for the exploitation of mineral resources (Au, Mn, and Cu) have been remarkable. This study presents evidence of anthropogenic impacts, mainly caused by ASM, on the quality and hydrogeochemical characteristics of the IRW surface water. The hydrogeochemical data sets of two projects carried out in the IRW, during 2017 and from 2020 until present, were used to evaluate these impacts within the region. Water quality indices were calculated for the surface water samples. For the whole IRW, water collected during the dry season tended to yield better quality indicators in comparison to those collected during the rainy season. Two sampling sites at Sereno Creek showed very poor water quality and extremely high concentrations of Fe, Al, and potentially toxic elements over time. From 2016 to 2022, ASM sites increased markedly. Moreover, there are indications that Mn exploitation via ASM in Sereno hill is the main source of contamination in the area. New trends of ASM expansion were observed along the main watercourses, related to the exploitation of Au from alluvial deposits. Similar anthropogenic impacts are registered in other regions of the Amazon and environmental monitoring should be encouraged to assess the chemical safety of strategic areas. � 2023 Elsevier Ltd
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    Geochemical mapping in stream sediments of the Caraj�s Mineral Province, part 2: Multi-element geochemical signatures using Compositional Data Analysis (CoDA)
    (Elsevier Ltd, 2021-04-30T00:00:00) Salom�o, Gabriel Negreiros; Dall'Agnol, Roberto; Ang�lica, R�mulo Sim�es; Sahoo, Prafulla K.; Wang, Xueqiu
    The geological imprint on the geochemical background in stream sediment of the Itacai�nas River Watershed (IRW), located in the most prominent mining area of Brazil, the Caraj�s Mineral Province, was evaluated. The stream sediment dataset from the Itacai�nas Geochemical Mapping and Background Project of the Instituto Tecnol�gico Vale was used to address multi-element associations and for the definition of surface geochemical compartments by applying a series of multivariate geostatistics tools and geoprocessing techniques, through the Compositional Data Analysis (CoDA) perspective. In this study, the geochemical dataset was processed for centered log-ratio (clr) transformation prior to the Principal Factor Analysis (PFA). The spatial distribution of factor scores derived from PFA indicates a pronounced control on stream sediment geochemistry by the underlying geological setting and lithology. Relevant hidden correlations were observed among the nine extracted factors. An unsupervised classification based on k-means clustering algorithm was performed for the factor scores of 761 stream sediment samples. A multiproxy approach that combines the cluster classification and geoprocessing tools revealed a strong similarity in the spatial distribution of different geochemical compartments and geological domains of the IRW. Threshold values of 51 elements were calculated by a variety of statistical methods for references to the main four geological domains of the IRW defined using the geological framework and the geochemical compartments. These values were then compared to the background concentrations of the entire study area and to the investigation levels proposed by the Brazilian environmental agencies for potentially toxic elements. The new threshold values for the geochemical compartments of the IRW can be used for improving the assessment of environmental impact by anthropic activities, and to establish more realistic threshold values for different chemical elements in stream sediments. This study provides useful information for new mineral development projects and ore prospects, with potential benefit to the mineral sector and industry. � 2021