First Ground-Based DOAS Measurements of NO2 at Kinshasa and Comparisons with Satellite Observations

We present the first ground-based remote sensing measurements of NO2 made in Kinshasa. They were performed from 2017 to 2019. The motivation of making observations on air pollution in Kinshasa comes from its geographical location, its demography, its climatic conditions, and the many different sources of NO2 existing in its surroundings. A method for recovering the vertical density of the NO2 tropospheric column (VCDtropo) based on the differential optical absorption spectroscopy (DOAS) applied to observations at the zenith and 35 degrees elevation angle is described. The mean value of VCDtropo observed in Kinshasa is 3 x 10(15) molecules cm(-2). We further present first comparisons with the Ozone Monitoring Instrument (OMI) and Tropospheric Monitoring Instrument (TROPOMI) satellite observations. When comparing OMI data with our observations and using a linear regression analysis, we find a slope of 0.34 and a correlation coefficient of 0.50 for 51 days of coincidences over 2017-19. Similar comparisons with TROPOMI for 44 days show a slope of 0.41 and a correlation coefficient of 0.72. This study opens up perspectives for further air quality-related studies in Kinshasa and central Africa.