Ambient air particle mass concentrations in the urban area of the capital city of Yaoundé (Cameroon, Central Africa): monthly and seasonal behaviour

ABSTRACT

Two size fractions of particulate matters (PM_2.5, PM_10-2.5) were sampled for 1 year at an urban site of Yaoundé from March 2018 to February 2019 to describe PM_2.5, PM_10-2.5 and PM₁₀ pollution variations and determine their main sources. Samples were collected for 24 h on grease-coated filters using a Gent sampler. The analyses were carried out by Gravimetric and statistical methods. The highest monthly average level of the three size fractions were observed in the Long Dry season. Particularly in February (17 ± 13 µg/m³) for PM_2.5, in December (51 ± 28 µg/m³) for PM_10-2.5 and in January (65 ± 30 µg/m³) for PM₁₀. Whilst the lowest in the Long Rainy season especially in September (5 ± 3 µg/m³) and October (5 ± 4 µg/m³) for PM_2.5, in August (6 ± 3 µg/m³) and September (6 ± 3 µg/m³) for PM_10-2.5, and in September for PM₁₀ (11 ± 5 µg/m³). Compared to WHO limits, the annual mean was slightly lower for PM_2.5 (9 ± 3 µg/m³) and exceedingly higher for PM₁₀ (30 ± 8 µg/m³). However, that pollution level was in line with the lowest WHO Annual Interim Target limits. The correlation between PM_2.5 and PM₁₀ varied depending on the seasons. The PM_2.5/PM₁₀ ratio was higher in the Long Rainy season and lower in the Long Dry season. The annual ratio was 0.38 ± 0.18 and reflect that coarse particles are more abundant. Thus, the PM pollution in Yaoundé was dominated by dust sources and was close to that of some relatively less polluted developing country capitals around the world. It can also be ranked as the eleventh most airborne polluted African capital.

KEYWORDS:

• Air pollution
• PM_2.5
• PM₁₀
• monthly distribution
• seasonal variation

Acknowledgments

We are grateful to IAEA which supported this work within the framework of RAF/7/016 regional project in terms of equipment and trainings. The authors thank the Institute of Geology and Mining Research, Cameroon for logistics. We also acknowledge Dr. (Mrs) Dipanjali Majumdar, Kolkata Zonal Lab, CSIR-NEERI, Nagpur for her assistance in drafting process.

Supplementary material

Supplemental data for this article can be accessed here.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.