Preliminary study of black carbon content in airborne particulate matters from an open site in the city of Yaoundé, Cameroon.

A light absorbing reflectometer was used to calculate black carbon (BC) mass concentrations contained in both fine and coarse particulate matters (PM2.5 and PM2.5-10) collected in an urban area of Yaounde from 1st March 2018 to 26th February 2019 to highlight BC fluctuation and determine its potential predominant sources. The highest BC concentrations were obtained on 14/02/2019 (5.37 µg/m3) and 17/01/2019 (3.90 µg/m3) whereas the cleanest days were 28/06/2018 (0.01 µg/m3) and 30/06/2018 (0.21 µg/m3) for BC content of PM2.5 and PM2.5-10, respectively. While BC values for BC2.5-10 were only obtained from November 2018 to February 2019 and in the long dry season, those of BC2.5 were obtained for all the seasons. Months, which were most polluted with BC, were January with an average value of 2.34 ± 1.71 µg/m3 and December with 1.65 ± 0.82 µg/m3 whilst the least polluted were September with 0.54 ± 0.33 µg/m3 and August with 0.21 ± 0.10 µg/m3 for BC2.5 and BC2.5-10, respectively. The BC2.5 and BC2.5-10 annual average values were 1.18 ± 0.98 µg/m3 and 0.66 ± 0.39 µg/m3. The annual mean BC contributions were 8.27 ± 5.00% and 6.63 ± 4.49%, respectively, in PM2.5 and PM2.5-10. The BC2.5/PM2.5 percentages varied widely; thus, a complete identification of potential sources of BC was very complex. However, by analogy with other studies, predominant sources were agricultural burn, light-duty gasoline, household wood and charcoal burning sources.