Distribuição de elementos terras raras e pedogênese em vertissolos do Nordeste brasileiro
Data
2023-12-13
Autores
Gonzales, Maria Tereza Diniz 
Orientadores
Barcellos, Diego
Tipo
Trabalho de conclusão de curso
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Os elementos terras raras (ETR) em solos apresenta um comportamento químico que permite
utilizar o fracionamento para compreender os processos de intemperismo, o que torna os ETRs
numerosamente úteis como indicadores de processos pedogenéticos e geoquímicos em solos.
Posto isto, o objetivo deste trabalho consistiu na identificação e determinação da distribuição e
comportamento de teores naturais de ETRs ao longo de perfis de Vertissolos no nordeste
brasileiro. Foram coletadas amostras de três perfis, o perfil 4 está localizado no município de
Iguatu (CE) contendo Vertissolo Háplico, e os perfis 5 e 6 em Madalena (CE) contendo
Vertissolo Ebânico. As amostras passaram por Análise por Ativação com Nêutrons
Instrumental (INAA), em reator nuclear. Os resultados foram normalizados com base em
valores de referência do NASC (North American Shale Composite), e comparados com índices
de intemperismo CIA (Chemical Alteration Indices), e PIA (Plagioclase Index of Alteration), e
matriz de correlação. O Vertissolo Háplico apresentou variações nas concentrações dos ETR,
diminuindo em condições de intemperismo e oxidação ao longo do perfil amostrado. O cério
apresenta anomalias negativas ao longo do perfil. Amostras normalizadas mostram aumento
geral dos níveis de ETR leves (ETRL) no horizonte, enquanto os ETR pesados (ETRP) manteve
valores próximos entre si. As razões Ce/CeN e La/YbN indicam anomalia negativa de Ce e
enriquecimento dos níveis de ETRL nas amostras. Enquanto o Vertissolo Ebânico apresentou
as menores relações entre ETRL/ETRP, estabelecendo um enriquecimento de ETRP (Eu, Tb),
com menores teores de ∑ETR. As taxas de lixiviação dos ETRL são superiores à dos ETRP,
devido ao grau moderado de intemperismo. A razão (Ce/Ce)N mostrou anomalia positiva de Ce.
As análises geoquímicas dos Vertissolos destacam complexidades nas distribuições de ETR,
ressaltando a importância da normalização para melhores interpretações. Os resultados desse
estudo têm implicações significativas nos processos pedogenéticos e na influência ambiental
desses solos, contribuindo para avanços na ciência do solo e geoquímica ambiental.
Rare earth elements (REEs) in soils have a chemical behavior that allows fractionation to be used to understand weathering processes, which makes REEs very useful as indicators of pedogenetic and geochemical processes in soils. With this in mind, the aim of this study was to identify and determine the distribution and behavior of natural REE levels along Vertissolo profiles in northeastern Brazil. Samples were collected from three profiles, profile 4 located in the municipality of Iguatu (CE) containing Vertissolo Háplico, and profiles 5 and 6 in Madalena (CE) containing Vertissolo Ebânico. The samples were analyzed by Instrumental Neutron Activation Analysis (INAA) in a nuclear reactor. The results were normalized based on reference values from the NASC (North American Shale Composite), and compared with weathering indices CIA (Chemical Alteration Indices), and PIA (Plagioclase Index of Alteration), and a correlation matrix. The Vertissolo Háplico showed variations in REE concentrations, decreasing under conditions of weathering and oxidation along the sampled profile. Cerium shows negative anomalies along the profile. Normalized samples show a general increase in the levels of light REE (REEL) in the horizon, while heavy REE (ERRH) maintained values close to each other. The Ce/CeN and La/YbN ratios indicate a negative Ce anomaly and enrichment of REEL levels in the samples. While the Ebonic Vertisol showed the lowest REEL/REEH ratios, establishing an enrichment of REEH (Eu, Tb), with lower ΣREE contents. The leaching rates of ETRL are higher than those of REEH, due to the moderate degree of weathering. The (Ce/Ce)N ratio showed a positive Ce anomaly. The geochemical analyses of the Vertisols highlight complexities in the REE distributions, highlighting the importance of normalization for better interpretations. The results of this study have significant implications for pedogenetic processes and the environmental influence of these soils, contributing to advances in soil science and environmental geochemistry.
Rare earth elements (REEs) in soils have a chemical behavior that allows fractionation to be used to understand weathering processes, which makes REEs very useful as indicators of pedogenetic and geochemical processes in soils. With this in mind, the aim of this study was to identify and determine the distribution and behavior of natural REE levels along Vertissolo profiles in northeastern Brazil. Samples were collected from three profiles, profile 4 located in the municipality of Iguatu (CE) containing Vertissolo Háplico, and profiles 5 and 6 in Madalena (CE) containing Vertissolo Ebânico. The samples were analyzed by Instrumental Neutron Activation Analysis (INAA) in a nuclear reactor. The results were normalized based on reference values from the NASC (North American Shale Composite), and compared with weathering indices CIA (Chemical Alteration Indices), and PIA (Plagioclase Index of Alteration), and a correlation matrix. The Vertissolo Háplico showed variations in REE concentrations, decreasing under conditions of weathering and oxidation along the sampled profile. Cerium shows negative anomalies along the profile. Normalized samples show a general increase in the levels of light REE (REEL) in the horizon, while heavy REE (ERRH) maintained values close to each other. The Ce/CeN and La/YbN ratios indicate a negative Ce anomaly and enrichment of REEL levels in the samples. While the Ebonic Vertisol showed the lowest REEL/REEH ratios, establishing an enrichment of REEH (Eu, Tb), with lower ΣREE contents. The leaching rates of ETRL are higher than those of REEH, due to the moderate degree of weathering. The (Ce/Ce)N ratio showed a positive Ce anomaly. The geochemical analyses of the Vertisols highlight complexities in the REE distributions, highlighting the importance of normalization for better interpretations. The results of this study have significant implications for pedogenetic processes and the environmental influence of these soils, contributing to advances in soil science and environmental geochemistry.
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Distribuição de elementos terras raras e pedogênese em vertissolos do Nordeste brasileiro