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Isotopic composition of methane (CH4) sources in a tropical Amazon forest: A preliminary data set

Jose Mauro S Moura, Centro de Energia Nuclear na Agricultura, jmauro@cena.usp.br (Presenting)
Reynaldo L Victoria, Centro de Energia Nuclear na Agricultura, reyna@cena.usp.br
Marcelo Z Moreira, Centro de Energia Nuclear na Agricultura, mmoreira@cena.usp.br
Christopher S Martens, University of North Carolina at Chapel, cmartens@email.unc.edu
Howard P Mendlovitz, University of North Carolina at Chapel, Mendlovitz@unc.edu
Risonaldo L Lima, Projeto LBA-ECO, risonaldo@lbasantaren.com.br
Irene Cibelle G Sampaio, Projeto LBA-ECO, cibelle@lbasantaren.com.br

The greatest sources of CH4 are fossil fuel burning and wetlands. As one of the biggest wetland areas in the world, the Amazon region has an important role in current scenario since recent estimations indicate the CH4 flux in the Amazon basin is approximately 22 TgC yr-1. However, not only flooded areas but also upland forests in the Amazon could contribute as source of CH4, with emissions ranging from 4 to 38 TgCH4 yr-1. Here we present preliminary results of the stable isotopic composition of CH4 in tropical upland. This first campaign was done at Flona do Tapajós tower site (km67), in Santarém-Para, where a set of tubes were placed and inlets for sampling allowed us to pull atmospheric air samples in a vertical profile (0.2, 7, 22, 35, and 45m) in different times of the day (4, 16, 22, and 24h) during 3 days. The air samples were pulled through the tubes by a battery-operated pump and then stored into glass flasks. The &delta13CH4 was determined in a Carlo Erba NA 1600 elemental analyzer equipped with a Finnigan MAT Conflo interface. The mean &delta13 value found was equal to -47.04±0.07‰; it is in the range for values found for atmospheric methane (-47.3‰ to -46.2‰) . The CH4 produced during nighttime ours tends to be more depleted in 13C than during daytime hours indicating that microbial production of methane within the canopy should be an important source of this gas

Science Theme:  TG (Trace Gases)

Presentation Type:  Poster

Abstract ID: 115

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