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Communication incl. Poster: BibTeX citation key:  Delona
Delon, C., Galy-Lacaux, C., Boone, A., Liousse, C., Serça, D., Adon, M., Diop, B., Akpo, A., Lavenu, F., Mougin, E. & Timouk, F. 2009. Atmospheric nitrogen budget in Sahelian dry savannas. Work presented at Third International AMMA Conference, July 20—24, at Ouagadougou, Burkina Faso.
Added by: Devic 2009-09-08 11:05:35    Last Edited by: roussot 2009-10-18 17:43:45
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Categories: Land surface processes, Land surface-atmosphere feedback
Keywords: Downscaling
Creators: Adon, Akpo, Boone, Delon, Diop, Galy-Lacaux, Lavenu, Liousse, Mougin, Serça, Timouk
Publisher: African Monsoon Multidisciplinary Analyses (Ouagadougou, Burkina Faso)
Collection: Third International AMMA Conference

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Abstract
The atmospheric nitrogen budget depends on emission and deposition fluxes both as reduced and oxidized nitrogen compounds. In this study, a first attempt of nitrogen budget for the year 2006 is made in the Sahel, through measurements and simulations in three stations of the IDAF network situated in dry savanna ecosystems .Dry deposition fluxes are calculated from measurements of NO2, HNO3 and NH3 gaseous concentrations, and wet deposition is calculated from NH4+ and NO3- concentration in rain samples. Emission fluxes are evaluated including NO biogenic emission from soils (an Artificial Neural Network module has been inserted in the ISBA-SURFEX surface model), NOx and NH3 emission from domestic and biomass fires, and NH3 volatilization from animal excreta.
The monthly evolution of oxidized N compounds shows that deposition measurements increase at the beginning of the rainy season (June) consecutive to biogenic NO strong emissions (pulse events). The annual budget is balanced, with emission fluxes in the same order of magnitude as deposition fluxes. Emission of oxidized compounds is dominated by biogenic emission from soils (domestic and biomass fires account for 27% at the most, depending on the station). NH3 emission is dominated by volatilization processes. Deposition fluxes are dominated by dry deposition processes (69% of the total), both for oxidized and reduced compounds.
When upscaled to the Sahelian region (10°N:20°N, 15°W:10°E), total deposition is estimated at 3.59 TgN/yr, and total emission is 3.92 TgN/yr. The difference is in the range of incertitude evaluated for the calculation of all fluxes.
The main conclusion of this work is that while often underestimated, arid and semi arid ecosystems constitute a significant part in the global nitrogen budget.
Last Edited by: roussot