Navegando por Autor "ROSA, Maria Beatriz Silva da"

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Acesso aberto (Open Access)
Dinâmica do carbono em pequenas bacias de drenagem sob uso de agricultura familiar na Amazônia Oriental
(Universidade Federal do Pará, 2007) ROSA, Maria Beatriz Silva da; FIGUEIREDO, Ricardo de Oliveira; http://lattes.cnpq.br/2388049759708934
This research was designed to evaluate carbon dynamics in Eastern Amazon, where the main land use is small holder farming, and was conducted in three small catchments. Carbon dynamics was evaluated considering hydrological and biogeochemical measurements in Cumaru, Pachibá and São João streams from June 2006 to May 2007. Aquatic environment and fluvial hydrogeochemistry were characterized through in situ measures of electrical conductivity, temperature, pH and dissolved oxygen concentration. Water samples were collected and analyzed to determine dissolved organic carbon (DOC) concentrations and carbon dioxide partial pressures (pCO2). Concentrations of dissolved inorganic carbon (DIC) were calculated from pCO2 values. Despite being calculated from pCO2 values, CO2 fluxes were also measured in situ. Instantaneous discharge was measured in each month field campaign and used to calculate DOC annual fluxes. Soil and land use characterization in the study watersheds, as well as precipitation and discharge rates, were considered for results interpretation. Main results were: 1) Stream water physic-chemical characteristics in the study catchments respond to the acid soils, riparian vegetation, and the hydrological and biogeochemical processes in the terrestrial and aquatic ecosystems, and present some seasonal variation. 2) Dissolved carbon concentrations was correlated with pH and dissolved oxygen in stream water; 3) DOC fluxes weighted by area were higher than in other Amazonian watersheds and even higher during rainy season; 4) DOC fluxes and CO2 evasion seem to respond positively to riparian vegetation and mature forest, and negatively to agriculture; 5) CO2 evasion rates were higher than in other Amazonian rivers corroborating the hypothesis that small catchments are important sources of atmospheric CO2 in the region.
Acesso aberto (Open Access)
Evasion of CO2 and dissolved carbon in river waters of three small catchments in an area occupied by small family farms in the eastern Amazon
(Universidade Federal do Pará, 2017-08) FIGUEIREDO, Ricardo de Oliveira; MARKEWITZ, Daniel; KRUSCHE, Alex Vladimir; COSTA, Fabíola Fernandes; GERHARD, Pedro; ROSA, Maria Beatriz Silva da
CO2 effluxes from streams and rivers have been hypothesized to be a critical pathway of carbon flow from the biosphere back to the atmosphere. This study was conducted in three small Amazonian catchments to evaluate carbon evasion and dynamics, where land-use change has occurred on small family-farms. Monthly field campaigns were conducted from June 2006 to May 2007 in the Cumaru (CM), Pachibá (PB) and São João (SJ) streams. Electrical conductivity, pH, temperature, and dissolved oxygen measurements were done in situ, while water samples were collected to determine dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) concentrations, as well as carbon dioxide partial pressures (pCO2) and CO2 evasion fluxes. Instantaneous discharge measured by a current meter was used to calculate DOC fluxes. Considering all the sites, DOC, DIC, pCO2, and CO2 flux measurements ranged as follows, respectively: 0.27 - 12.13 mg L-1; 3.5 - 38.9 mg L-1; 2,265 - 26,974 ppm; and 3.39 - 75.35 μmol m-2 s-1. DOC annual flux estimates for CM, SJ and PB were, respectively, 281, 245, and 169 kg C ha-1. CO2 evasion fluxes had an average of 22.70 ± 1.67 μmol m-2 s-1. These CO2 evasion fluxes per unit area were similar to those measured for major Amazonian rivers, thus confirming our hypothesis that small streams can evade substantial quantities of CO2. As secondary vegetation is abundant as a result of family farming management in the region, we conclude that this vegetation can be a major driver of an abundant carbon cycle.