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Abstract.We present MAX-DOAS measurements of NO 2 , HCHO, and aerosols performed in Central Africa, in the city of Bujumbura, Burundi (3.38 Aerosol-extinction and trace-gas vertical profiles are retrieved by applying the optimal-estimation-based profiling tool bePRO to the measured O 4 , NO 2 and HCHO slant-column densities. The MAX-DOAS vertical columns and profiles are used for 5 investigating the diurnal and seasonal cycles of NO 2 , HCHO, and aerosols. Regarding the aerosols, the retrieved AODs are compared to co-located AERONET sun-photometer measurements for verification purposes, while in the case of NO 2 and HCHO, the MAX-DOAS vertical columns and profiles are compared to GOME-2 and OMI satellite observations.To characterise the biomass-burning and biogenic emissions in the Bujumbura region, the trace gases and aerosol MAX-DOAS retrievals are used in combination with MODIS fire radiative-power values and the tropospheric 3D chemical transport 10 model IMAGES, as well as simulations from the NOAA backward-trajectory model HYSPLIT. The first results show that the aerosol and HCHO seasonal variation is driven by the alternation of rain and dry periods, the latter being associated with intense biomass-burning agricultural activities and forest fires in the south/south-east and transport from this region to Bujumbura. In contrast, NO 2 is seen to depend mainly on local emissions close to the city, due to the short lifetime of this species (typically 1-2 hours).

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