Spatial and Temporal Trends in Particulate Matter Pollution in a Sub-Saharan Metropolitan African City: A Case Study of Ibadan, Nigeria

Abstract

Particulate matter pollution in the metropolitan city of Ibadan, Nigeria was investigated across two site classes for two seasons in a one-year study period to establish its spatial and temporal variations. During this period, a total of 74 samples comprising 37 fractions each of PM_2.5 and PM_2.5-10 were collected with a double staged filter unit ‘Gent’ stacked air sampler   from March 2014 to February 2015. The fractions were obtained by gravimetric analysis of the pre-weighed and pre-conditioned quartz filter media. Mean PM_2.5 fraction collected at the industrial area had a maximum concentration of 85 µg m^-3 in January 2014 and 43 µgm^-3 was registered at the residential area in October 2014.  Mean PM₁₀ peaked at 187 µg m^-3 in November 2014 at the industrial area and 125  µg m^-3 in January 2015 at the residential area of the metropolis.  The mass data between the industrial and residential areas accounted for 0.367 ± 8.43 and 0.308 ± 7.30 respectively during the dry season period and 0.347 ± 15.32 and 0.375 ± 16.34 during the wet season period. Overall, PM₁₀ concentrations were more predominant than PM_2.5 and it exceeded the WHO 24hr Air Quality Guidelines of 50 µg m³ in many instances. The set of data of PM_2.5 and PM₁₀ fractions for the metropolis informed that anthropogenic activities might be responsible for deteriorating air quality and could pose great danger to the inhabitants at the Ibadan air-shed.  Thus, the result implies that residents might be prone to health related diseases such as bronchitis or lung cancer over a period of time.