HR: 1340h
AN: B43A-0127    [Abstracts]
TI: Spatial and temporal variation on isotopic composition of CH4 in Eastern Amazon streams
AU: * Moura, J
EM: jmauro@esalq.usp.br
AF: CENA, Av. Centenario, 303, Piracicaba, SP 13400-970 Brazil
AU: Martens, C
EM: cmartens@unc.edu
AF: University of North Carolina, Venable Hall CB#3300, Chapel Hill, NC 275993300 United States
AU: Moreira, M
EM: mmoreira@cena.usp.br
AF: CENA, Av. Centenario, 303, Piracicaba, SP 13400-970 Brazil
AU: Mendlovitz, H
EM: Mendlovitz@unc.edu
AF: University of North Carolina, Venable Hall CB#3300, Chapel Hill, NC 275993300 United States
AU: Lima, R
EM: risonlado@lbaeco.com.br
AF: Projeto LBAECO, AV Brajonas de Miranda 343, Santar‚m, PA 68040-320 Brazil
AU: Sampaio, I
EM: cibelle@lbaeco.com.br
AF: Projeto LBAECO, AV Brajonas de Miranda 343, Santar‚m, PA 68040-320 Brazil
AU: Ometto, J
EM: jpometto@cena.usp.br
AF: CENA, Av. Centenario, 303, Piracicaba, SP 13400-970 Brazil
AB: The isotopic composition of methane varied seasonally and spatially among wetland environments as a result of changes in microbial production and oxidation mechanisms. We measured the variation in isotopic composition of CH4 (delta13C-CH4) trapped in bubbles formed in the streams sediment during the period of August 2000 and August 2003. The samples were analyzed in a Finnigan Delta Plus mass spectrometer. The study sites were the Maica, A‡u, and Jamaraqua Stream; three different streams in the Eastern Amazonia. The mean isotopic values found during this period were in a range of -78% to -46%. At the Acu Stream, the delta13C-CH4 varied from -66.0 to -47% and at Maica Stream varied from -69 to -40%. The Jamaraqua Stream showed the larger variation with values in a range of -89 to -54%. For helping us to explain the differences between the sites we analyzed the isotopic composition of the sediment at most different sites (Maica and Jamaraqua). Cores sediments (~30cm) and samples of leaves were taken at each site and analyzed by mass spectrometry for delta13C, C/N ratio, and %C. There was a strong evidence of difference between the streams on all of these parameters. The sediment of Maica stream showed heavier values of delta13C (p<0,05), which resulted from the decomposition of grass enriched in 13C. As for the amount of carbon stored in sediment, the Jamaraqua Stream had much more carbon than Maica Stream (p<0,05), and its C/N ratio is two folds bigger than in Maica.
DE: 1800 HYDROLOGY
DE: 1600 GLOBAL CHANGE (New category)
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting