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Günter Helas Jürgen Lobert Dieter Scharffe Luise Schäfer Johann Goldammer Jean Baudet Brou Ahoua Ayité-Lô Ajavon Jean-Pierre Lacaux Robert Delmas Meinrat O. Andreae 《Journal of Atmospheric Chemistry》1995,22(1-2):163-174
Ozone has been observed in elevated concentrations by satellites over areas previously believed to be background. There is meteorological evidence, that these ozone plumes found over the Atlantic Ocean originate from vegetation fires on the African continent.In a previous study (DECAFE-88), we have investigated ozone and assumed precursor compounds over African tropical forest regions. Our measurements revealed large photosmog layers at altitudes from 1.5 to 4 km. Both chemical and meteorological evidence point to savanna fires up to several thousand km upwind as sources.Here we describe ozone mixing ratios observed over western Africa and compare ozone production ratios from different field measurement campaigns related to vegetation burning. We find that air masses containing photosmog ingredients require several days to develop their oxidation potential, similar to what is known from air polluted by emissions from fossil fuel burning. Finally, we estimate the global ozone production due to vegetation fires and conclude that this source is comparable in strength to the stratospheric input. 相似文献
2.
Robert Delmas Jean Pierre Lacaux Jean Claude Menaut Luc Abbadie Xavier Le Roux Gunter Helas Jurgen Lobert 《Journal of Atmospheric Chemistry》1995,22(1-2):175-193
Gaseous nitrogen compounds (NO
x
, NO
y
, NH3, N2O) were measured at ground level in smoke plumes of prescribed savanna fires in Lamto, in the southern Ivory Coast, during the FOS/DECAFE experiment in January 1991. During the flaming phase, the linear regression between [NO
x
] and [CO2] (differences in concentration between smoke plumes and atmosheric background) results volumic emission ratio [NO
x
]/[CO2]=1.37×10–3 with only slight differences between heading and backing fires. Nearly 90% of the nitrogen oxides are emitted as NO. Average emission ratios of other compounds are: 1.91, 0.047, and 0.145×10–3 for NO
y
, NH3 and N2O, respectively. The emission ratios obtained during this field experiment are compred with corresponding values measured during former experiments with the same plant species in combustion chambers. An accurate determination of both the biomass actually burned and of the plant nitrogen content, allows an assessment of emission fluxes of N-compounds from Guinean savanna burns. Preliminary results dealing with the influence of fire on biogenic emissions from soils are also reported. 相似文献
3.
Helas Günter Lobert Jürgen Scharffe Dieter Schäfer Luise Goldammer Johann Baudet Jean Ajavon Ayité-Lô Ahoua Brou Lacaux Jean-Pierre Delmas Robert Andreae Meinrat O. 《Journal of Atmospheric Chemistry》1995,22(1-2):217-239
We measured CO2, CO, CH4, H2, and NO2 in air masses polluted by savanna fires over Côte d'Ivoire, western Africa. Elevated concentrations of these trace gases were found in fire plumes and also in extensive haze layers. Trace gas mixing ratios ranged as high as 605 ppmv for CO2, 14.8 ppmv for CO, 2.7 ppmv for CH4, 4.2 ppmv for H2, and 25 ppbv for NO2. We compare our emission ratios to those obtained in previous field and laboratory studies. The emission ratios, expressed as an average and as a range or as an average only, were: dCO/dCO2 5.3×10–2 (3–18×10–2); dCH4/dCO 5.3×10–2; dH2/dCO 2.4×10–1 and dNO2/dCO2 1.8×10–4 (1.5–2.2×10–4). The values found match those found during similar measurements, though our results point to rather vigorous burning in the savanna of western Africa. 相似文献
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