Airborne measurements of savanna fire emissions and the regional distributio of pyrogenic pollutants over Western Africa

We measured CO2, CO, CH4, H2, and NO2 in air masses polluted by savanna fires over Cote 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.