Spatial and temporal variations of the particulate size distribution and chemical composition over Ibadan, Nigeria

Abstract

Spatial and temporal variation of suspended particulate matter was measured in Ibadan, Nigeria during the raining and dry months of 2013 and 2014, respectively. Six different locations were considered, reflecting city-spread, population density, lifestyle, and vehicular- and industrial-related activities. Elemental characterisation of the samples were carried out using energy dispersive x-ray fluorescence (ED-XRF) spectroscopy, while the black carbon content was determined using an optical transmissometer. Backward trajectory analysis indicated that most air mass was of maritime origin except on few occasions that suggested the Sahara desert origin. Average PM2.5/PM10 ratio for the entire sampling period was 0.32 ± 0.04. This is slightly lower than the reported values in the coastal city of Lagos, partly because of more adequately paved and better road networks resulting in lower dust re-suspension and/or there are relatively finer fraction particulates from other sources, which might include marine, industrial, and secondary emission-related sources. Black carbon showed predominance in the fine fractions and was, majorly, of traffic origin. Major enriched elements of concern are S, Zn, As, and Pb aside from those of sea origin. Refuse burning was observed to be the principal source of Pb and Zn in all the sites except one, which showed major industrial-related activities source. This study will provide data for future measurement and modelling works as well as providing a benchmark for relevant agencies for policy making on setting emission standards for the country.

Spatial and Temporal Variability of the PM2.5/PM10 Ratio in Wuhan, Central China

“…A previous study in Wuhan also reported higher ratios in suburban site (0.64) than urban site (0.57) in 1995(0.57) in -1996(0.57) in (Wei et al, 1999. It was also found the highest PM 2.5 /PM 10 ratio at the control site in Ibadan, Nigeria, because of being far from the road and any obvious source of pollutants (Akinlade et al, 2015).…”

“…Compared with numerous studies demonstrating the variability of PM concentrations (Eeftens et al, 2012;Hu et al, 2014;Akinlade et al, 2015;Ghim et al, 2015;Huang et al, 2015;Zhang and Cao, 2015;Zhou et al, 2015;Xu et al, 2016a), few studies have reported on the spatio-temporal variability of the PM 2.5 /PM 10 ratio (Blanco-Becerra et al, 2015;Zhang and Cao, 2015;Munir, 2016;Zhou et al, 2016). The goal of this study is to investigate the spatiotemporal variability of the PM 2.5 /PM 10 ratio at a city scale systematically and comprehensively.…”

“…Speranza et al (2016) found that the ratio of PM 2.5 to PM 10 , rearranged from published data according to seasons of sampling, was more than 0.6 in colder seasons (autumn-winter) with a lower ratio (< 0.5) in warmer seasons (spring-summer). While in Africa, the PM 2.5 /PM 10 ratio is higher during the wet season than dry season due to dust re-suspension, a major contribution to PM 10 (Akinlade et al, 2015). As for daily variation, it was found that the minimum values of PM 2.5 /PM 10 ratio in one day occurred during traffic hours in consequence of re-suspended coarse road dust (Querol et al, 2001;Evagelopoulos et al, 2006).…”

An inter-comparison of PM2.5 at urban and urban background sites: Chemical characterization and source apportionment

“…The comparison of chemical composition of PM in different typologies of sites in specific areas (such as traffic, industrial, urban, urban background, and rural sites) gives information about the dynamics of airborne particles in the atmosphere and the spatial gradients allowing better distinction of local and distant sources. This allows to distinguish the contributions of local sources from urban and regional backgrounds and from long-range transport (Costa et al, 2016;Akinlade et al, 2015;Pan et al, 2015;Pauraitė et al, 2015;Vodička et al, 2015;Avino et al, 2015;Kaneyasu et al, 2014;Heal and Hammonds, 2014;Dall'Osto et al, 2013;Gianini et al, 2013;Beuck et al, 2011;Arruti et al, 2011;Yin et al, 2010;Guo et al, 2009). This is particularly important in the Mediterranean region that is influenced by air masses coming from Europe, Asia, and Africa (Lelieveld et al, 2002), affected by a large variety of pollution sources (Salameh et al, 2015) and characterized by a complex meteorology, which favors the aging of polluted air masses (Artiñano et al, 2003;Amodio et al, 2012;Contini et al, 2014a;Perrone et al, 2014).…”

Detection of a gas flaring signature in the AERONET optical properties of aerosols at a tropical station in West Africa

“…In contrast to cities in the developed economies, there is a dominance of the coarse-mode fraction in the atmospheric aerosol loading in major Nigerian cities. This has been attributed to frequent and persistent resuspension of dust from the large expanse of unpaved roads [Akinlade et al, 2015;Obioh et al, 2013;Owoade et al, 2013].…”