HR: 11:05h
AN: B12A-04    [Abstracts]
TI: Dry and Wet Deposition of Atmospheric Inorganic Nitrogen in a Tropical Environment (Rond\^{o}nia, Brazil: 10\deg45.44'S, 62\deg21.27'W)
AU: * Trebs, I
EM: ivonne@mpch-mainz.mpg.de
AF: Max Planck Institute for Chemistry, J.J. v. Becherweg 28, Mainz, 55128 Germany
AU: Lara, L L
EM: luciene@cena.usp.br
AF: Centro de Energia Nuclear na Agricultura (CENA), Laboratorio de Ecologia Isot¢pica, Universidade de Sao Paulo (USP), Av. Centenario, 303, Sao Paulo, 13400-970 Brazil
AU: Zeri, L M
EM: mzeri@bgc-jena.mpg.de
AF: Max Planck Institute for Biogeochemistry, Hans-Kn”ll-Straáe 10, Jena, 07745 Germany
AU: Moura, M A
EM: malm@ccen.ufal.br
AF: Universidad Federal de Alagoas, Depto. de Meteorologia, Campus A.C. Simoes BR 104-km 14, Tabuleiro do Martins, Maceio, 57072-970 Brazil
AU: Gatti, L V
EM: lvgatti@baitaca.ipen.br
AF: Instituto de Pesquisas Energ‚ticas e Nucleares, Atmospheric Chemistry Laboratory, Av. Prof. Lineu Prestes, 2242, Cidade Universitaria, Sao Paulo, 055508-900 Brazil
AU: Artaxo, P
EM: artaxo@if.usp.br
AF: Universidade de Sao Paulo, Instituto de F¡sica, Rua do Matao, Travessa R, 187, Sao Paulo, 05508-900 Brazil
AU: Slanina, J
EM: Sjaak@slanina.com
AF: University of Wageningen, Department of Environmental Sciences, Duivendaal 2, Wageningen, 6701 Netherlands
AU: Andreae, M O
EM: andreae@mpch-mainz.mpg.de
AF: Max Planck Institute for Chemistry, J.J. v. Becherweg 28, Mainz, 55128 Germany
AU: Meixner, F X
EM: meixner@mpch-mainz.mpg.de
AF: Max Planck Institute for Chemistry, J.J. v. Becherweg 28, Mainz, 55128 Germany
AB: Total N deposition (wet + dry) has been experimentally determined in temperate regions and few data sets exist about wet N deposition to tropical ecosystems. When global atmospheric chemistry & transport models such as MOGUNTIA had been applied, they suggested that total N deposition in the Northern Hemisphere far exceeded contemporary tropical N deposition [Holland et al., 1999]. However, quantitative experimental information about dry N deposition in tropical environments, required to test these model predictions, has been lacking. We estimated the total N deposition (wet + dry) for a pasture site in the Amazon Basin (Rond\^{o}nia, Brazil) based on field measurements covering the closing of the dry season (biomass burning), a transition period, and the onset of the wet season (clean conditions) (LBA-SMOCC). Wet N deposition was determined by collection and subsequent analyses of rainwater samples. Gaseous species, such as NO, NO$_{2}$, O$_{3}$, NH$_{3}$, HNO$_{3}$, HONO and the inorganic aerosol compounds NH$_{4}$$^{+}$ and NO$_{3}$$^{-}$ were measured at one aerodynamic reference height using real-time techniques, which was accompanied by measurements of micrometeorological quantities. Dry deposition fluxes of NO$_{2}$ and HNO$_{3}$ were inferred using the "big leaf multiple resistance approach". Furthermore, we predict bi-directional surface-atmosphere exchange fluxes of NH$_{3}$ and HONO with the aid of a canopy compensation point model, which considers the bi-directional exchange of NH$_{3}$ between biosphere and atmosphere as a dynamic process [Sutton et al., 1998]. These approaches were based on the variation of surface parameters, which determine trace gas uptake/release by vegetative canopies and which were not experimentally determined. Dry deposition fluxes of aerosol particles were derived using established empirical parameterizations. The total annual N deposition was estimated to be 7.5 to 8.5 kgN ha$^{-1}$ yr$^{-1}$, whereof 2 to 3 kgN ha$^{-1}$ yr$^{-1}$ are attributed to dry N deposition and \sim 5.5 kgN ha$^{-1}$ yr$^{-1}$ to wet deposition. Thus, dry deposition may contribute on average 30 % to the total annual N deposition. It is expected that 2 to 6.5 kgN ha$^{-1}$ yr$^{-1}$ are (re-)emitted from the pasture site, mainly in form of gaseous NH$_{3}$, but also HONO and NO. Our results suggest that the modeled average contemporary N deposition to tropical grasslands is underestimated by a factor of two or three.
DE: 3322 Land/atmosphere interactions
DE: 3307 Boundary layer processes
DE: 0315 Biosphere/atmosphere interactions
DE: 0365 Troposphere--composition and chemistry
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting