Study of methane emission on Pantanal of Matogrosso do Sul / Estudo da emissão de metano no Pantanal Sul Matogrossense

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The results of an evaluation of the tropical wetland regions contribution to the methane burden are presented. In this study, a total of eight campaigns were performed during the years of 2004 and 2005 inside the Pantanal region of Matogrosso do Sul State in seven sites, near the Miranda River. Static chamber technique with polyurethane syringe sampling was used. In the fluxes analyses, the sites were divided in lakes and floodplains, and some environmental variables that can affect methane emissions, as water depth, pH, dissolved oxygen and water temperature were also measured. The overall average of the 560 individual methane valid fluxes measured from March, 2004 to December, 2005 was 116.8 ± 257.8 mgCH4m-2d-1 and median of 11.1 mgCH4m-2d-1, near that observed in others tropical flooded regions. In about 40% of flux measurements occurred non-linear increases in the chamber concentrations that were assumed to be linked to methane loses through bubbles. The bubble flux represented about 90% of the total methane loses in the measurements and ranged from 1.1 to 2187.0 mgCH4m-2d-1, with an average of 279.5 ± 289.5 mgCH4m-2d-1 and median of 127.5 mgCH4m-2d-1. The diffusive fluxes ranged from 1.0 to 145.5 mgCH4m-2d-1, with an average of 13.1 ± 20.7 mgCH4m-2d-1 and median of 5.0 mgCH4m-2d-1. The fluxes from lakes are smaller than that observed in the floodplains, where the flooding was controlled by the seasonal cycle. The diffusive flux showed a slight seasonal variation, with small average fluxes during the dry season. A direct correlation between fluxes and environmental factor (water depth, water temperature, dissolved oxygen and presence of aquatic vegetation) was not found, however, these factors showed to have some influence on the methane fluxes. Estimates of methane emission from the Pantanal were performed based on estimates of flooded area obtained of a remote sensing model and the extrapolation of our fluxes measurements to the whole region. When considering just the average flux and the average flooded area in the measurement period, the annual methane emission was of 1.37 TgCH4/year. When the observed difference between habits and the influence of vegetation was considered, the annual emission was of 2.20 TgCH4/year. These estimates conserve a large uncertain resulting of the extrapolation for the whole Pantanal of the measurements made in one region only, but they indicate that the Pantanal is one of the most important natural sources of atmospheric methane in South America.

ASSUNTO(S)

space geophysics Área alagada efeito estufa greenhouse effect metano troposfera troposphere methane variação sazonal seasonal variation geofisica espacial wetland

ACESSO AO ARTIGO

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