This study concerns the estimation of column densities of four tropospheric trace gases, SO2, NO2, O3, and NH3 by MAX-DOAS measurement techniques in Bamako city in Mali during two measurement campaigns. The estimated column densities are the slant column density (SCD), and the vertical column density (VCD). In-situ measurements of the absorbance (optical density) of trace gases from solar radiation, at several angles of elevation between horizontal (0°) and zenith (90°), were performed by Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS). The results during the two MAX-DOAS measurement campaigns indicate that the gas NO2 presents the higher values of SCD and VCD; and respectively the gases NO2, O3, and NH3, the values of and VCD values for NO2. The higher values of daily variations of SCD are 15.70 E+17 for the gas NO2; 9.37 E+17 for SO2; 6.29 E+17 for the gas O3; and 2.34 E+17 for NH3. The higher values of daily of SCD by observation angles are obtained at the angle 50º and they are 9.25 E+17 for the gas NO2; 5.66 E+17 for SO2; 3.26 E+17 for O3; and 1.48 E+17 for the gas NH3. The higher values of daily variations of VCD are 10.86 E+17 for NO2; 7.66 E+17 for the gas SO2; 4.42 E+17 for O3; and 1.62 E+17 for the gas NH3. The higher values of VCD by observation angles are also obtained at the angle 50º and they are 1.21 E+18 for the gas NO2; 7.41 E+17 for SO2; 4.74 E+17 for O3; and 1.94 E+17 for the gas NH3.
