Caracterização da matéria orgânica natural no estuário do rio Jaguaribe em diferentes estações climáticas em anos de seca prolongada

• Ano de defesa: 2019
• Autor(a) principal: Cavalcante, Mariany Sousa
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Palavras-chave em Português: Carbono; Isótopos estáveis; Ultrafiltração; Aromaticidade
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/49622

This work evaluated how seasonal and hydrodynamic factors affected the fluxes, contents, and origin of natural organic matter (NOM) in the Jaguaribe River estuary, as well as its interaction with dissolved metals, measured by ICP MS. The period was characterized by a strong reduction in freshwater input to the estuarine region caused by rainfall shortages and artificial river control by dams, leading the estuary to hypersalinity conditions in 2016. The isotopic composition (δ 13C and δ 15N) and fluorescence analyzes of NOM showed that it originates mainly from terrestrial sources. However, the contribution of marine NOM was also relevant, increasing in drier years due to increased saline intrusion into the estuary. In agreement with the isotopic characterization, the dissolved organic carbon (DOC) was composed mainly of humic substances and showed no correlation with the biological activity, probably due to its refractory nature. However, the non-conservative decrease in COD and NOM aromaticity, represented by specific UV absorbance at 254 nm (SUVA), with increasing salinity suggests that this MON was chemically active. Truly dissolved organic matter (<1 kDa) was the main fraction of DOC, corresponding to 80 ± 2%. A reduction in NOM particle size was observed with the estuarine mixture, probably promoted by the decomposition of MON. Cr, Fe, V, Al, Cu and Ni presented a significant correlation with DOC and a concentration reduction with the increase of salinity. MON concentrations were controlled by the estuarine hydrodynamics, increasing with residence time and freshwater percentage. However, the reduction of freshwater input to the estuary resulted in carbon flows to the ocean lower than expected in tropical regions. The estuarine mixing zone behave as a carbon retainer during the drought and as an exporter in the rainy season. These results may be a prognostic of the environmental changes in the estuaries under semiarid tropical climate regions due to the decrease of the riverine inflow and high marine intrusion in a scenario of global climate change.