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<article language="en">
	<journal>
		<journal_title>Atmospheric Chemistry and Physics Discussions</journal_title>
		<journal_url>www.atmos-chem-phys-discuss.net</journal_url>
		<issn>1680-7367</issn>
		<eissn>1680-7375</eissn>
		<volume_number>9</volume_number>
		<issue_number>3</issue_number>
		<publication_year>2009</publication_year>
	</journal>
	<doi>10.5194/acpd-9-14189-2009</doi>
	<article_url>http://www.atmos-chem-phys-discuss.net/9/14189/2009/</article_url>
	<abstract_html>http://www.atmos-chem-phys-discuss.net/9/14189/2009/acpd-9-14189-2009.html</abstract_html>
	<fulltext_pdf>http://www.atmos-chem-phys-discuss.net/9/14189/2009/acpd-9-14189-2009.pdf</fulltext_pdf>
	<start_page>14189</start_page>
	<end_page>14233</end_page>
	<publication_date>2009-06-30</publication_date>
	<article_title content_type="html">Atmospheric nitrogen budget in Sahelian dry savannas</article_title>
	<authors>
		<author numeration="1" affiliations="1">
			<name>C. Delon</name>
			<email>claire.delon@aero.obs-mip.fr</email>
		</author>
		<author numeration="2" affiliations="1">
			<name>C. Galy-Lacaux</name>
		</author>
		<author numeration="3" affiliations="2">
			<name>A. Boone</name>
		</author>
		<author numeration="4" affiliations="1">
			<name>C. Liousse</name>
		</author>
		<author numeration="5" affiliations="1">
			<name>D. SerÃ§a</name>
		</author>
		<author numeration="6" affiliations="1,3">
			<name>M. Adon</name>
		</author>
		<author numeration="7" affiliations="4">
			<name>B. Diop</name>
		</author>
		<author numeration="8" affiliations="5">
			<name>A. Akpo</name>
		</author>
		<author numeration="9" affiliations="7,8">
			<name>F. Lavenu</name>
		</author>
		<author numeration="10" affiliations="6">
			<name>E. Mougin</name>
		</author>
		<author numeration="11" affiliations="6">
			<name>F. Timouk</name>
		</author>
	</authors>
	<affiliations>
		<affiliation numeration="1" content_type="html">Laboratoire d&apos;AÃ©rologie, UniversitÃ© de Toulouse and CNRS, Toulouse, France</affiliation>
		<affiliation numeration="2" content_type="html">CNRM/GMME, MÃ©tÃ©o-France, Toulouse, France</affiliation>
		<affiliation numeration="3" content_type="html">LAboratoire de Physique de l&apos;Atmosphere, Abidjan, CÃ´te d&apos;Ivoire</affiliation>
		<affiliation numeration="4" content_type="html">UniversitÃ© de Bamako, Mali</affiliation>
		<affiliation numeration="5" content_type="html">UniversitÃ© Abomey Calavi, Cotonou,BÃ©nin</affiliation>
		<affiliation numeration="6" content_type="html">CESBIO, Toulouse, France</affiliation>
		<affiliation numeration="7" content_type="html">formerly at: CESBIO, Toulouse, France</affiliation>
		<affiliation numeration="8" content_type="html">deceased</affiliation>
	</affiliations>
	<abstract content_type="html">The atmospheric nitrogen budget depends on emission and deposition fluxes
both as reduced and oxidized nitrogen compounds. In this study, a first
attempt at estimating the Sahel nitrogen budget for the year 2006 is made,
through measurements and simulations at three stations from the IDAF network
situated in dry savanna ecosystems. Dry deposition fluxes are estimated from
measurements of NO&lt;sub&gt;2&lt;/sub&gt;, HNO&lt;sub&gt;3&lt;/sub&gt; and NH&lt;sub&gt;3&lt;/sub&gt; gaseous
concentrations, and wet deposition fluxes are calculated from NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;
and NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt; concentrations in samples of rain. Emission fluxes are
estimated including biogenic emission of NO from soils (an Artificial
Neural Network module has been inserted into the ISBA-SURFEX surface model),
emission of NO&lt;sub&gt;x&lt;/sub&gt; and NH&lt;sub&gt;3&lt;/sub&gt; from domestic fires and biomass
burning, and volatilization of NH&lt;sub&gt;3&lt;/sub&gt; from animal excreta.
&lt;br&gt;&lt;br&gt;
This study uses original and unique data from remote and hardly-ever-explored
regions. The monthly evolution of oxidized N compounds shows that deposition
increases at the beginning of the rainy season because of large emissions of
biogenic NO (pulse events). Emission of oxidized compounds is dominated by
biogenic emission from soils (domestic fires and biomass burning account for
27% at the most, depending on the station), whereas emission of NH&lt;sub&gt;3&lt;/sub&gt; is
dominated by the process of volatilization. Deposition fluxes are dominated
by gaseous dry deposition processes (58% of the total), for both oxidized
and reduced compounds. The average deposition flux in dry savanna ecosystems
ranges from 8.6 to 10.9 kgN ha&lt;sup&gt;&amp;minus;1&lt;/sup&gt; yr&lt;sup&gt;&amp;minus;1&lt;/sup&gt;, with 30% attributed to
oxidized compounds, and the other 70% attributed to NH&lt;sub&gt;x&lt;/sub&gt;. The
average emission flux ranges from 7.8 to 9.7 kgN ha&lt;sup&gt;&amp;minus;1&lt;/sup&gt; yr&lt;sup&gt;&amp;minus;1&lt;/sup&gt;,
dominated by NH&lt;sub&gt;3&lt;/sub&gt; volatilization (67%) and biogenic emission from soils
(24%). The annual budget is then balanced, with emission fluxes on the
same order of magnitude as deposition fluxes.
&lt;br&gt;&lt;br&gt;
When scaled up to the Sahelian region (10&amp;deg; N:20&amp;deg; N,
15&amp;deg; W:10&amp;deg; E), the estimates of total emission range from 3.6 to
4.5 TgN yr&lt;sup&gt;&amp;minus;1&lt;/sup&gt; and total deposition ranges from 3.9 to 5 TgN yr&lt;sup&gt;&amp;minus;1&lt;/sup&gt;.
The N budget gives a net deposition flux ranging from
0.2 to 0.6 TgN yr&lt;sup&gt;&amp;minus;1&lt;/sup&gt;. If scaled up to the global scale (in the
tropical band), it is possible to calculate a total budget of oxidized and
reduced N compounds for dry savannas, with a global nitrogen deposition flux
ranging from 11.1 to 14.1 TgN yr&lt;sup&gt;&amp;minus;1&lt;/sup&gt;, and a global emission flux
ranging from 10.1 to 12.5 TgN yr&lt;sup&gt;&amp;minus;1&lt;/sup&gt;. These ecosystems contribute a
significant amount (around 12%) to the global nitrogen budget.</abstract>
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</article>

