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| Titel: |
Dry and wet deposition of inorganic nitrogen compounds to a tropical pasture site (Rondônia, Brazil) |
| Auteur: |
I. Trebs L. L. Lara L. M. M. Zeri L. V. Gatti P. Artaxo R. Dlugi J. Slanina M. O. Andreae F. X. Meixner |
| Verschenen in: |
Atmospheric chemistry and physics |
| Paginering: | Jaargang 6 (2006) nr. 2 pagina's 447-469 |
| Jaar: |
2006 |
| Inhoud: |
The input of nitrogen (N) to ecosystems has increased dramatically over the past decades. While total (wet + dry) N deposition has been extensively determined in temperate regions, only very few data sets of N wet deposition exist for tropical ecosystems, and moreover, reliable experimental information about N dry deposition in tropical environments is lacking. In this study we estimate dry and wet deposition of inorganic N for a remote pasture site in the Amazon Basin based on in-situ measurements. The measurements covered the late dry (biomass burning) season, a transition period and the onset of the wet season (clean conditions) (12 September to 14 November 2002) and were a part of the LBA-SMOCC (Large-Scale Biosphere-Atmosphere Experiment in Amazonia – Smoke, Aerosols, Clouds, Rainfall, and Climate) 2002 campaign. Ammonia (NH<sub>3</sub>), nitric acid (HNO<sub>3</sub>), nitrous acid (HONO), nitrogen dioxide (NO<sub>2</sub>), nitric oxide (NO), ozone (O<sub>3</sub>), aerosol ammonium (NH<sub>4</sub><sup>+</sup>) and aerosol nitrate (NO<sub>3</sub><sup>-</sup>) were measured in real-time, accompanied by simultaneous meteorological measurements. Dry deposition fluxes of NO<sub>2</sub> and HNO<sub>3</sub> are inferred using the ''big leaf multiple resistance approach'' and particle deposition fluxes are derived using an established empirical parameterization. Bi-directional surface-atmosphere exchange fluxes of NH<sub>3</sub> and HONO are estimated by applying a ''canopy compensation point model''. N dry and wet deposition is dominated by NH<sub>3</sub> and NH<sub>4</sub><sup>+</sup>, which is largely the consequence of biomass burning during the dry season. The grass surface appeared to have a strong potential for daytime NH<sub>3</sub> emission, owing to high canopy compensation points, which are related to high surface temperatures and to direct NH<sub>3</sub> emissions from cattle excreta. NO<sub>2</sub> also significantly accounted for N dry deposition, whereas HNO<sub>3</sub>, HONO and N-containing aerosol species were only minor contributors. Ignoring NH<sub>3</sub> emission from the vegetation surface, the annual net N deposition rate is estimated to be about −11 kgN ha<sup>-1</sup> yr<sup>-1</sup>. If on the other hand, surface-atmosphere exchange of NH<sub>3</sub> is considered to be bi-directional, the annual net N budget at the pasture site is estimated to range from −2.15 to −4.25 kgN ha<sup>-1</sup> yr<sup>-1</sup>. |
| Uitgever: |
Copernicus GmbH (provided by DOAJ) |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 5 van 17 gevonden artikelen
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