Analysis of the influence of environmental parameters on methane flux from floodplains and lakes in the Abobral River, Pantanal, Brazil

Abstract

This study evaluates the influence of physical and chemical characteristics of the water column in the processes that result in methane emissions in the Pantanal. Two surveys were conducted in 2009 and 2010, corresponding to the drought and flood seasons, respectively. The CH4 fluxes were determined using the static chamber technique. Environmental variables, such as depth, water temperature, pH, redox potential, dissolved oxygen and total dissolved solids were also measured. Diffusive and bubble flux presented an average value of 11.1 ± 13.5 mg CH4 m-2 d-1 e 275.9 ± 348.5 mg CH4 m-2 d-1, which is a value near those observed in other tropical flooded regions. Statistical t-tests have shown significant differences between drought and flood seasons (p ≤ 0.05). Diffusive fluxes represented about 87% of the total fluxes measured in drought. During the flood season there were more instances of bubble fluxes (77%). Statistical analysis (correlation and Principal Components Analysis) indicate that physical and chemical characteristics could affect methane fluxes. Diffusive fluxes correlated mainly with pH, redox potential and dissolved oxygen, which is in accordance with the increase of organic matter during flooding. Bubble fluxes measured during the drought season correlated mainly with water depth and temperature, pH and redox potential, which is an indication of an environment to suitable to the formation and liberation of the bubbles from sediment.