Simultaneous chemical and microbial characterization of atmospheric PM10 and PM2.5 particulate from three land-use types in Rwanda, Central-East Africa

Rapid population growth and urbanization is causing worsening air quality in Africa. This is of particular concern in sub-Saharan Africa countries where exposure to airborne particulate matter (PM) poses a serious public health threat in urban and rural areas. However, there is scarce air quality data for this region. In this study PM with aerodynamic diameters of =10 µm and =2.5?µm (PM10 and PM2.5, respectively) was collected using high volume air samplers over a three-month period at three locations in Rwanda. The chemical composition (polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs (NPAHs)) and microbial community structure (estimated using bacterial and fungal rRNA gene sequences) were characterized, and relationships were investigated using multivariate statistics. Microbial analysis revealed that the diversity and abundance of the airborne bacterial and fungal communities varied by site, PM size fraction, and season. The majority of the microorganisms originated from soil, dust and plants. Redundancy analysis (RDA) identified that PAH and NPAH species were significantly negatively correlated with microbial community known to be highly efficient PAH degraders in the soil. Variation partitioning analysis (VPA) indicated that environmental factors and the bacteria community structure (genus) explained together 44.95% of the total variation of the chemical composition.