Abstract:
This paper presents a chemical characterization of fine particulate matter (PM2.5) in air masses passing through Thohoyandou and
further determines their sources. PM2.5 samples were collected and quantified using the gravimetric method. X-ray fluorescence, smoke
stain reflectometer, optical transmissometer and scanning electron microscopy - energy dispersive X-Ray spectroscopy were used to
determine the chemical and morphological composition of the particulate matter. The source apportionment was done using principal
component analysis while the HYSPLIT model was used to depict the long-range transport clusters. The mean of concentrations of
PM2.5, soot, black carbon and UVPM were 10.9 μg/m3
, 0.69x10-5 m-1, 1.22 μg/m3
and 1.40 μg/m3
, respectively. A total of 24 elements were
detected in the PM2.5 with Pd, Sn, Sb, Mg, Al, and Si being the dominant elements. SEM-EDS have shown the presence of irregular, flat
and spherical particles which is associated with crustal material and industrial emissions. Source apportionment analysis revealed six
major sources of PM2.5 in Thohoyandou namely, crustal materials, industrial emissions, vehicular emissions, urban emissions, fossil
fuel combustion and fugitive-Pd. Air parcels that pass through Thohoyandou were clustered into four groupings. The major pathways
were from the SW Indian Ocean, Atlantic Ocean, and inland trajectories. Clusters from the ocean are associated with low concentration,
while inland clusters are associated with high concentration of PM2.5. The PM2.5 levels occasionally exceeded the daily WHO guideline
(25 μg/m3
) in Thohoyandou and the sources of PM2.5 extend beyond the borders. This study recommends that further studies need to
be carried out to assess the health impacts of PM2.5 in Thohoyandou.
