Aprimoramento do protocolo de determinação da sensibilidade à luminescência de grãos de quartzo e feldspato em sedimentos finos
Data
2021-02-24
Autores
Melo, Dayane Batista 
Orientadores
Mendes, Vinícius Ribau
Tipo
Trabalho de conclusão de curso
Título da Revista
ISSN da Revista
Título de Volume
Resumo
A paleoclimatologia é o estudo das variações climáticas ao longo da história da Terra, partindo da análise e interpretação de vestígios naturais que podem descrever o clima no passado. Dentre os melhores arquivos naturais dessas variações estão os testemunhos marinhos, que armazenam informações sobre salinidade, temperatura de superfície, intensidade das correntes oceânicas e até precipitação continental, por meio de componentes químicos e fósseis microscópicos. Para além das análises consagradas pela literatura, recentemente foi descoberto um novo indicador de paleoprecipitação baseado na sensibilidade à luminescência de grãos de quartzo e feldspato. A LOE (Luminescência Opticamente Estimulada) e a TL (Termoluminescência) aplicadas em sedimentos de testemunhos marinhos, foram utilizadas com sucesso em dois testemunhos marinhos coletados próximo à foz do rio Parnaíba (GL1248 e GeoB1602-1), permitindo a avaliação das mudanças de precipitação no semiárido brasileiro ao longo dos últimos 120 mil anos. Nesse sentido, o presente trabalho busca aprimorar os protocolos já existentes para a leitura de sensibilidade à luminescência. As amostras foram testadas com diferentes temperaturas de leitura do sinal LOE (125°C e 20°C - temperatura ambiente) e com diferentes procedimentos de preparação: Amostras brutas (com matéria orgânica e carbonato) x Amostras processadas (sem matéria orgânica e carbonato). As amostras foram submetidas ao fotoesvaziamento do sinal emitido pelo feldspato através do LED infravermelho e do quartzo pelo LED azul, seguidos de uma nova dose de radiação para a leitura do sinal LOE. Os resultados foram comparados com dados previamente obtidos do testemunho GeoB1602-1. Por meio deste trabalho, conclui-se que ambos os testes LOE (125°C x 20°C) e com diferente preparo (amostra processada x amostra bruta), demostraram ser compatíveis com os previamente estabelecidos, o que sugere a possível adoção de um protocolo simplificado com as amostras brutas em temperatura ambiente, o que facilitará a difusão do método, por tornar o processo mais simples e menos custoso.
Paleoclimatology is the study of climatic variations throughout the Earth's history, starting from the analysis and interpretation of natural traces that could describe the climate in the past. Among the best natural files of these variations are the marine cores, which store information about salinity, surface temperature, intensity of ocean currents and even continental precipitation, using chemical components and microscopic fossils. In addition to the analyzes enshrined in the literature, a new indicator of paleoprecipitation was recently discovered based on the sensitivity to luminescence of quartz and feldspar grains. LOE (Optically Stimulated Luminescence) and TL (Thermoluminescence) applied to marine core sediments, were used successfully in two marine cores collected near the mouth of the Parnaíba River (GL1248 and GeoB1602-1), allowing the assessment of precipitation changes in the Brazilian semi-arid region over the past 120 thousand years. In this sense, the present work seeks to improve the already existing protocols for reading luminescence sensitivity. The samples were tested with different reading temperatures of the LOE signal (125 ° C and 20 ° C - room temperature) and with different preparation procedures: Crude samples (with organic matter and carbonate) x Processed samples (without organic matter and carbonate) . The samples were submitted to photo-emptying of the signal emitted by the feldspar through the infrared LED and the quartz by the blue LED, followed by a new dose of radiation to read the LOE signal. The results were compared with data previously obtained from the GeoB1602-1 core. Through this work, it is concluded that both LOE tests (125 ° C x 20 ° C) and with different preparation (processed sample x raw sample), proved to be compatible with those previously established, which suggests the possible adoption of a simplified protocol with raw samples at room temperature, which will facilitate the diffusion of the method, as it makes the process simpler and less costly.
Paleoclimatology is the study of climatic variations throughout the Earth's history, starting from the analysis and interpretation of natural traces that could describe the climate in the past. Among the best natural files of these variations are the marine cores, which store information about salinity, surface temperature, intensity of ocean currents and even continental precipitation, using chemical components and microscopic fossils. In addition to the analyzes enshrined in the literature, a new indicator of paleoprecipitation was recently discovered based on the sensitivity to luminescence of quartz and feldspar grains. LOE (Optically Stimulated Luminescence) and TL (Thermoluminescence) applied to marine core sediments, were used successfully in two marine cores collected near the mouth of the Parnaíba River (GL1248 and GeoB1602-1), allowing the assessment of precipitation changes in the Brazilian semi-arid region over the past 120 thousand years. In this sense, the present work seeks to improve the already existing protocols for reading luminescence sensitivity. The samples were tested with different reading temperatures of the LOE signal (125 ° C and 20 ° C - room temperature) and with different preparation procedures: Crude samples (with organic matter and carbonate) x Processed samples (without organic matter and carbonate) . The samples were submitted to photo-emptying of the signal emitted by the feldspar through the infrared LED and the quartz by the blue LED, followed by a new dose of radiation to read the LOE signal. The results were compared with data previously obtained from the GeoB1602-1 core. Through this work, it is concluded that both LOE tests (125 ° C x 20 ° C) and with different preparation (processed sample x raw sample), proved to be compatible with those previously established, which suggests the possible adoption of a simplified protocol with raw samples at room temperature, which will facilitate the diffusion of the method, as it makes the process simpler and less costly.
Descrição
Citação
MELO., Dayane Batista. Aprimoramento do protocolo de determinação da sensibilidade à luminescência de grãos de quartzo e feldspato em sedimentos finos. 2021. 36f. Trabalho de conclusão de curso de graduação (Bacharelado Interdisciplinar em Ciência e Tecnologia do Mar) - Instituto do Mar, Universidade Federal de São Paulo, Santos, 2021.