Abstract ID: 458

Regional scale N₂O fluxes in eastern and central Amazônia: 2001 - 2007

Nitrous oxide (N₂O) is the fourth most important anthropogenic greenhouse gas, presenting global warming potential about 310 times higher than CO₂. Globally the main sources of N₂O are nitrification and denitrification in soils (9-31 TgN₂Oyr-1) and approximately 20% originates in wet rainforest ecosystems. Therefore, N₂O emission in the Amazon represents a significant part of the global N cycle. In this project, we determine N₂O Fluxes using aircraft vertical profiles from two Amazonian sites. We calculate fluxes using a column integration method as described by Miller et al (2007). These fluxes represent the integration of all N₂O fluxes between Atlantic coast of Brazil and the sites. The profiles have been sampled since December 2000 over Tapajós National Forest (SAN), in Pará State and since December 2004 over Cuieiras Biological Reserve (MAN) in Amazonas State until 2007. The fluxes calculated for all profiles from coast to SAN exhibit large seasonality, but fluxes using data from MAN show discreet seasonality. Monthly fluxes from coast to MAN exhibited positive correlation between N₂O flux and rainfall, i.e., higher fluxes during the wet season and lower in the dry season. The fluxes between the coast and SAN showed this same behavior except during the last trimester (the peak of dry season) where the average flux was higher than during the wet season. This high flux period does not appear to be correlated either with rainfall or burning, suggesting an unknown source in the upwind regions from SAN at this time of year. The annual mean flux derived from MAN data is 2.1±1.0 mgN₂Om-2day-1, while from SAN it is 1.5±1.6 mgN₂Om-2day-1. A sensitivity study indicates our fluxes represent regional-scale and not local-scale values, and they are in general agreement with global and local-scale studies at different Amazonian sites.

Session:  Biogeochemistry - Sources, sinks, and atmospheric chemistry of trace gases.

Presentation Type:  Oral