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Doctoral Thesis
DOI
10.11606/T.18.2004.tde-03032005-092611
Document
Author
Full name
Marcelo Bento da Silva
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2004
Supervisor
Committee
Sikar, Bohdan Matvienko (President)
Abe, Donato Seiji
Bulhões, Luiz Otávio de Sousa
Schalch, Valdir
Schulz, Harry Edmar
Title in Portuguese
Aspectos do comportamento de gás metano dissolvido na água de reservatórios brasileiros
Keywords in Portuguese
câmaras de difusão
efeito estufa
gás metano
reservatórios hidrelétricos
sensor 'CH IND.4'
Abstract in Portuguese
Extensos corpos d’água como reservatórios hidrelétricos, aqui estudados, podem ser fontes consideráveis de gases de efeito estufa ('CH IND.4' e 'CO IND.2') devido à decomposição de parte da biomassa da floresta submersa e também pela biomassa alóctone e autóctone. Este trabalho apresenta concentrações e estimativas de fluxos difusivos e ebulitivos desses gases dissolvidos na coluna d’água, nos reservatórios hidrelétricos de Miranda (MG), Xingó (AL/SE), Ribeirão das Lages (RJ) e Represa do Lobo (SP) durante o período de outubro de 2001 a agosto de 2003. Utilizou-se, em perfis verticais, um sensor 'CH IND.4' de estado sólido comercial provido de detector de metano semicondutor, cuja superfície, ao adsorver o gás, varia sua resistência interna fornecendo sinal relacionado à concentração de gás. Foram usadas câmaras de troca difusiva na determinação de fluxos de troca de 'CH IND.4' e 'CO IND.2' na interface água-atmosfera e funis de captura de bolhas para processos ebulitivos. Mediram-se algumas variáveis físicas e químicas. Os perfis de gás metano dissolvido em água apresentaram elevadas concentrações, geralmente com valores crescentes desde próximo a superfície até a interface água-sedimento. Porém, sumidouros oxidativos presentes na coluna d’água, que consomem o gás metano no seu percurso até a superfície, juntamente com convecções impelidas pelo vento, foram responsáveis por perfis de diferentes tipos com concentrações alternadas, em conseqüência dessa ação. Fluxos difusivos também foram calculados a partir de experimentos de troca difusiva de gases dissolvidos na interface água-atmosfera resultando em emissões de 'CH IND.4' e 'CO IND.2' para atmosfera, e em alguns casos, absorção de 'CO IND.2' pelo reservatório
Title in English
Aspects of dissolved methane behavior in water bodies of brazilian reservoirs
Keywords in English
brazilian reservoirs
diffusion chambers
greenhouse gas
methane
methane sensor
Abstract in English
Extended water bodies such as the hydroelectric reservoirs here studied can be greenhouse gas sources ('CH IND.4' and 'CO IND.2') due to decay of part of submerged forest biomass and also due to allochtonous and autochtonous organic compounds. This work presents concentrations, ebullitive and diffusive fluxes of the gases dissolved in the water column in the following reservoirs : Miranda, Xingó, Ribeirão das Lages and Lobo, between October 2001 and August 2003. In the course of this work methane profiles were determined by a commercial methane sensor, a solid state device, the electrical resistance of which varies as a function of absorbed methane providing a signal related to dissolved gas concentration. Diffusion chambers were used to measure 'CH IND.4' and 'CO IND.2' exchange rates at the air-water interface; bubble capture funnels were used for ebullitive emission. Some physical and chemical variables were also measured. Dissolved methane profiles showed high concentrations, generally with increasing values from water surface to sediment. However, the oxidative methane sink in the water column consumes this gas in its upward migration path and together with wind-propelled convection produces different profile types. Diffusive flux was also calculated from diffusive exchange experiments of these gases at the air-water interface, which showed 'CH IND.4' and 'CO IND.2' emission, sometimes 'CO IND.2' absorption, by the reservoir
 
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MBS_.pdf (5.60 Mbytes)
Publishing Date
2005-04-09
 
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