Dinâmica do carbono orgânico dissolvido em área de alta inundação do Rio Cuiabá, Pantanal Mato-grossense

• Autor(a) principal: Moraes, Sara Cortez de
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFMT
• Texto Completo: http://ri.ufmt.br/handle/1/4534
• topic: Decoada; Carbono orgânico dissolvido; Matéria orgânica dissolvida; Pantanal; Rio Cuiabá; CNPQ::ENGENHARIAS::ENGENHARIA SANITARIA::RECURSOS HIDRICOS; Decoada; Dissolved organic carbon; Dissolved organic matter; Pantanal; Cuiabá river

The Pantanal Wetland is one of the largest floodplains in the world, formed by the junction of the flooding areas of each of its forming rivers in the Upper Paraguay River Basin. The geomorphology and hydrological regime of each river directly contribute to and influence directly the downstream flood pulse, including the Pantanal floodplain. The Cuiabá River is one of the main tributaries of this system. In the high-water phase (rising and flood phases), during the rainy season in this region, there is the transport of suspended matter and nutrients, such as carbon, from the plateau areas (subject to intensive land use), as well as their sedimentation. and transformation in the plain. Due to the influence of the hydro-ecological processes in the extensive rivers-plain interaction area in the Pantanal, a natural phenomenon, regionally referred to as “decoada”, occurs during the beginning of the hydrological flood phase. This phenomenon is characterized by changing water quality in flood areas, including marginal lagoons, due to the decomposition of submerged organic matter, mainly grasses, which tends to move downstream as the flood progresses. Changes in physical, chemical and biological parameters take place as a result of the initial interaction between flood water and previously dried, soil and plant biomass. The objective of this work was to determine the spatial variation and the dynamics of Dissolved Organic Carbon (DOC) concentrations in the dry and flood phases of a hydrological year, in Baía do Burro, a marginal lagoon on the right bank of the Cuiabá River, in its high flooding area, and determine their possible origins using the optical properties of Dissolved Organic Matter (DOM). Two field campaigns were conducted in 2018, one in the hydrological flood phase (March 13-16th) and one in the drought phase (September 22-25th) on the bay surface (40 points), as well as in a vertical profile in the center of the body of water, with 5 transversal points (37 samples in flood and 23 in drought phases). In addition to samples for analysis of DOC (by UV-Vis Spectrolyser Sensor - Spectro :: lyser®-S :: can MESSTECHNIK), DOM (by Aqualog Horiba Spectrofluorimeter) and Alkalinity in the laboratory, in situ measurements of temperature, pH, dissolved oxygen, electrical conductivity and turbidity were performed via a previously calibrated HORIBA U-50 multiparameter probe, as well as transparency by Secchi Disc and indirect calculation of free carbon dioxide. Through statistical analysis and data spatialization, it was observed that the contribution of the floodplain (Campo do Jofre and adjacent areas) and corixos, besides the Cuiabá River itself, is responsible for the alterations of limnological parameters and the concentration of the DOC in Baía do Burro, showing significant differences (p<0.05) in the Decoada (rising and flood) period. The DOC values ranged from 8.09 to 14.37 mg/L (mean = 13.38 mg/L) in the flood phase and from 4.43 to 8.09 mg/L (mean = 7.23 mg/L) in drought. The optical properties of DOM, by means of the IF, IH, IB and SR indices and Ex/Em ratios, by using the PARAFAC model, indicated that both surface and profile MOD is mainly allochthonous (originated from recalcitrant, high molecular weight soils and vascular components of plants).