Abstract :
[en] Africa experiences an explosive human population growth, leading to different environmental issues. In particular, many African cities are heavily affected by air pollution. It is therefore essential to monitor the concentrations of various polluting species such as NO2, HCHO, O3 and aerosols, which have a direct impact on human health. The sources of pollutants in Africa are different from those found in many industrial areas. For example, forest fires and household cooking largely contribute to the NO2 and HCHO concentrations in Central Africa. However, many large African cities do not have atmospheric measurement instruments that perform continuous measurements.
From May 2017 to early November 2019, a single axis DOAS instrument was installed and performed measurements at the University of Kinshasa (UniKin: -4.42° S, 15.31° E). This installation is the result of a close collaboration between the Belgian Institute for Space Aeronomy (IASB) and the UniKin Faculty of Sciences. Studies based on measurements made with this instrument have demonstrated the presence of a clear yearly cycle of the NO2 concentration with higher values in the dry season (Yombo et al., 2021). With such a low-cost instrument, the information content of the measurements is very limited and the uncertainties of the measurements rather high. . In November 2019, the single axis instrument was replaced by a new MAX-DOAS (multi-axis differential optical absorption spectroscopy) system built at the IASB, increasing substantially the information content of the measurements.
These first Max-DOAS measurements are used to retrieve NO2 and HCHO contents over the city of Kinshasa, utilizing the harmonized FRM4DOAS analysis facility. The two years of MAXDOAS vertical column results of these two molecules are compared to OMI and TROPOMI data. They constitute important validation points in central Africa which currently lacks validation data and hence, these measurements will contribute to improvements of the a priori shape in the lower troposphere. Further, we compare this data set to specific GEOS-Chem chemistry transport model simulations allowing some specific investigations of source attribution. To our knowledge, these DOAS measurements yielded the first multiyear dataset of air quality measurements performed in Kinshasa.
