Analysis of Mass Concentration and Carbon Composition of PM2.5 During the Long Dry Season in Abomey-Calavi and Cotonou Cities, Benin

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Carbonaceous components are important components of fine atmospheric particulate matter (PM2.5) and can affect the local environment, climate, and human health. The PM2.5, Organic (OC) and elemental (EC) Carbon concentrations were measured at Arconville (AT) and Mahoule (MT) traffic during the dry season in southern Benin cities of Abomey-Calavi and Cotonou. The data are collected with passive samplers and archived as daily averages from December 2016 to March 2017. To gain a better understanding of possible local and regional aerosol sources, the concentration of PM2.5, OC and EC, as well as the OC/EC ratio were evaluated overall. For the studied period, average concentrations of PM2.5 particles were 64 ±16 µ.gm-3 and 79 ±18 µ.gm-3 at AT and MT, respectively. Those of OC and EC were 31 ± 13 μg·m-3 and 9 ± 06 μg·m-3 for AT and 38 ± 16 μg·m-3 and 13 ± 08 μg·m-3 for MT, respectively. Also, total carbon accounted for 62.5% of PM2.5 at AT and 64.56% at MT. The OC/EC ratios obtained in AT and MT were 3.44 and 2.92, respectively. These OC/EC ratios obtained in two cities are greater than 2, which confirmed the presence of secondary organic aerosols during this period on these two traffic sites.