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7.4 Conclusions

Methane emission by ebullitive transport was detected only in about 40% of the measurements, but it contributed 90% to total methane release to the atmosphere in the southern Pantanal region, so confirming the early results presented by Marani and Alvala (2007). Although a correlation between the fluxes and the environmental parameters was very weak, the diffusive transport events presented a statistically significant difference between the wet and dry seasons, however, the ebullitive fluxes did not present statistically significant differences between the wet and dry seasons, while the environmental parameters showed statistically significant differences between the two seasons. The severe drought that the region was subjected to during two years of the study may have influenced the flooding and the emission patterns. The methane emission estimates using different approximations, since a simplified general average flux, up to considering the diffusive, ebullitive and vegetation influences, resulted in methane release to atmosphere in the range of 1.4-2.2 Tg CH4 y-1, corresponding to about 2.2% of the global emission from natural wetlands. Thus, Pantanal may have the same potential of emission as Amazonia. Finally, additional areas of the Pantanal should be investigated to increase the confidence in the emission pattern obtained in this study.

Acknowledgments We thank Dr. Ralf Gielow for suggestions and the revision that improved the manuscript, the UFMS (Federal University of Matogrosso do Sul) for the logistical support, the Laboratorio de Ozonio staff for the cooperation and facilities support, and INPE (National Space Research Institute of Brazil) and CNPq (projeto 474816/03-6) for financial support.

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