Heterogeneous processes involving nitrogenous compounds and Saharan dust inferred from measurements and model calculations

Galy‐Lacaux, Corinne; Carmichael, G. R.; Song, Chul H.; Lacaux, Jean‐Pierre; Ourabi, H. Al; Modi, Assane Issa

doi:10.1029/2000jd900778

Cited by 57 publications

(56 citation statements)

References 57 publications

(28 reference statements)

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“…Such interactions were demonstrated in several field experiments totally or partly dedicated to studies of dust aerosol. Examples include GTE/ABLE 1 (Talbot et al, 1986), ACE-2 (Putaud et al, 2000), IDAF (Galy-Lacaux et al, 2001), MI-NATROC (for nitrate) , TRACE-P (Jordan et al, 2003), SHADE (Formenti et al, 2003). Other measurements also showed sulfate and nitrate enhancements on dust aerosol, at the Puy de Dome (France) (Sellegri et al, 2003), in the Barbados or in East Asia (Mori et al, 2003;Song and Carmichael, 2001).…”

Section: Evolution Of Concentration For Secondary Inorganic Componentsmentioning

confidence: 99%

Evolution of organic and inorganic components of aerosol during a Saharan dust episode observed in the French Alps

et al. 2004

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Abstract.A Saharan dust event was observed in a rural area in the Maurienne Valley (French Alps) in summer 2000. Detailed data on PM 10 , particle numbers, and aerosol chemistry (ionic species and Elemental Carbon (EC) and Organic Carbon (OC)) are presented. The comparative evolutions of particle numbers and chemistry (calcium, sodium, and sulfate) show that the overall period included two episodes of dust particles with very distinct chemistry, followed by an episode with a large increase of the concentrations of species with an anthropogenic origin. The overall data set does not indicate large interactions between the dust particles and compounds from anthropogenic origin (sulfate, nitrate) or with organic carbon, all of these species showing very low concentrations. Simplistic calculations indicate that these concentrations are consistent with our current knowledge of adsorption processes of gases on mineral dust in a clean air mass.

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Section: Evolution Of Concentration For Secondary Inorganic Componentsmentioning

confidence: 99%

Evolution of organic and inorganic components of aerosol during a Saharan dust episode observed in the French Alps

et al. 2004

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“…HNO 3 , which is extremely soluble in water, is thus easily scavenged by clouds. Galy-Lacaux et al (2001) have demonstrated that heterogenous processes between nitric acid and mineral particles are present all over the African continent.…”

Section: Wet Depositionmentioning

confidence: 99%

Atmospheric nitrogen budget in Sahelian dry savannas

Delon

Galy‐Lacaux

Boone³

et al. 2010

Atmos. Chem. Phys.

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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 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 2 , HNO 3 and NH 3 gaseous concentrations and from simulated dry deposition velocities, and wet deposition fluxes are calculated from NH This study uses original and unique data from remote and hardly-ever-explored regions.The monthly evolution of oxidized N compounds shows that emission and deposition increase 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 of oxidized compounds account for 0 to 13% at the most at the annual scale, depending on the station), whereas emission of NH 3 is dominated by the process of volatilization from soils. At the annual scale, the average gaseous dry deposition accountsCorrespondence to: C. Delon (claire.delon@aero.obs-mip.fr) for 47% of the total estimated deposition flux, for both oxidized and reduced compounds. The average estimated wet plus dry deposition flux in dry savanna ecosystems is 7.5±1.8 kgNha −1 yr −1 , with approximately 30% attributed to oxidized compounds, and the rest attributed to NH x . The average estimated emission flux ranges from 8.4(±3.8) to 12.4(±5.9) kgNha −1 yr −1 , dominated by NH 3 volatilization (72-82%) and biogenic emission from soils (11-17%), depending on the applied volatilization rate of NH 3 . While larger, emission fluxes are on the same order of magnitude as deposition fluxes. The main uncertainties are linked to the NH 3 emission from volatilization.When scaled up from the 3 measurement sites to the Sahelian region (12 • N:18 • N, 15 • W:10 • E), the estimated total emission ranges from 2(±0.9) to 3(±1.4) TgNyr −1 , depending on the applied volatilization rate of NH 3 and estimated total deposition is 1.8(±0.4) TgNyr −1 . The dry savanna ecosystems of the Sahel contribute around 2% to the global (biogenic + anthropogenic) nitrogen budget.

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“…Within the IDAF framework, several studies of the chemical composition of precipitation representative of African ecosystems have been published. These studies have helped to quantify the wet deposition of biogeochemically important elements and to estimate the contributions of different atmospheric sources (Galy-Lacaux and Modi, 1998;Galy-Lacaux et al, 2001;Sigha et al, 2003;Yoboue et al, 2005;Mphepya et al, 2004Mphepya et al, , 2006Galy-Lacaux et al, 2009). To complement these studies, it is appropriate to study and quantify dry deposition fluxes.…”

Section: Introductionmentioning

confidence: 99%

Long term measurements of sulfur dioxide, nitrogen dioxide, ammonia, nitric acid and ozone in Africa using passive samplers

et al. 2010

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Abstract. In this paper we present the long term monitoring of ambient gaseous concentrations within the framework of the IDAF (IGAC-DEBITS-AFRICA) program. This study proposes for the first time an analysis of long-term inorganic gas concentrations (1998 to 2007) of SO 2 , NO 2 , HNO 3 , NH 3 and O 3 , determined using passive samplers at seven remote sites in West and Central Africa. Sites are representative of several African ecosystems and are located along a transect from dry savannas-wet savannas-forests with sites at Banizoumbou (Niger), Katibougou and Agoufou (Mali), Djougou (Benin), Lamto (Cote d'Ivoire), Zoetele (Cameroon) and Bomassa (Congo). The strict control of measurement techniques as well as the validation and inter-comparison studies conducted with the IDAF passive samplers assure the quality and accuracy of the measurements. For each type of African ecosystem, the long term data series have been studied to document the levels of surface gaseous concentrations. The seasonal and interannual variability have also been analyzed as a function of emission source variations. We compared the measured West and Central African gas Correspondence to: M. Adon (adonatma@yahoo.fr) concentrations to results obtained in other parts of the world. Results show that the annual mean concentrations of NO 2 , NH 3 , HNO 3 measured in dry savannas are higher than those measured in wet savannas and forests that have quite similar concentrations. Annual mean NO 2 concentrations vary from 0.9±0.2 in forests to 2.4±0.4 ppb in the dry savannas, NH 3 from 3.9±1.4 to 7.4±0.8 ppb and HNO 3 from 0.2±0.1 to 0.5±0.2 ppb. Annual mean O 3 and SO 2 concentrations are lower for all ecosystems and range from 4.0±0.4 to 14.0±2.8 and from 0.3±0.1 to 1.0±0.2 ppb, respectively. A focus on the processes involved in gas emissions from dry savannas is presented in this work, providing explanations for the high concentrations of all gases measured at the three dry savannas sites. At these sites, seasonal concentrations of all gases are higher in the wet season. Conversely, concentrations are higher in the dry season in the wet savannas. In forested regions, we measure no significant difference between wet and dry seasons. This unique database of long term gases concentrations monitoring is available at:

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Heterogeneous processes involving nitrogenous compounds and Saharan dust inferred from measurements and model calculations

Cited by 57 publications

References 57 publications

Evolution of organic and inorganic components of aerosol during a Saharan dust episode observed in the French Alps

Evolution of organic and inorganic components of aerosol during a Saharan dust episode observed in the French Alps

Atmospheric nitrogen budget in Sahelian dry savannas

Long term measurements of sulfur dioxide, nitrogen dioxide, ammonia, nitric acid and ozone in Africa using passive samplers

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