Regional N2O fluxes in Amazonia derived from aircraft vertical profiles 1Instituto de Pesquisas Energéticas e Nucleares (IPEN), São Paulo, Brazil
2National Oceanic and Atmospheric Administration (NOAA), Colorado, USA
3Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Colorado, USA
Received: 14 July 2009 – Published in Atmos. Chem. Phys. Discuss.: 20 August 2009 Abstract. Nitrous oxide (N2O) is the third most important anthropogenic
greenhouse gas. Globally, the main sources of N2O are nitrification and
denitrification in soils. About two thirds of the soil emissions occur in
the tropics and approximately 20% originate in wet rainforest ecosystems,
like the Amazon forest. The work presented here involves aircraft vertical
profiles of N2O from the surface to 4 km over two sites in the Eastern
and Central Amazon: Tapajós National Forest (SAN) and Cuieiras Biologic
Reserve (MAN), and the estimation of N2O fluxes for regions upwind of
these sites. To our knowledge, these regional scale N2O measurements in
Amazonia are unique and represent a new approach to looking regional scale
emissions. The fluxes upwind of MAN exhibited little seasonality, and the
annual mean was 2.1±1.0 mg N2O m−2 day−1, higher than
that for fluxes upwind of SAN, which averaged 1.5±1.6 mg N2O m−2 day−1.
The higher rainfall around the MAN site could explain
the higher N2O emissions, as a result of increased soil moisture
accelerating microbial nitrification and denitrification processes. For
fluxes from the coast to SAN seasonality is present for all years, with high
fluxes in the months of March through May, and in November through December.
The first peak of N2O flux is strongly associated with the wet season.
The second peak of high N2O flux recorded at SAN occurs during the dry
season and can not be easily explained. However, about half of the dry
season profiles exhibit significant correlations with CO, indicating a
larger than expected source of N2O from biomass burning. The average
CO:N2O ratio for all profiles sampled during the dry season is
94±77 mol CO:mol N2O and suggests a larger biomass burning contribution to
the global N2O budget than previously reported.
Revised: 04 November 2009 – Accepted: 09 November 2009 – Published: 19 November 2009
Citation: D'Amelio, M. T. S., Gatti, L. V., Miller, J. B., and Tans, P.: Regional N2O fluxes in Amazonia derived from aircraft vertical profiles, Atmos. Chem. Phys., 9, 8785-8797, doi:10.5194/acp-9-8785-2009, 2009.