Outdoor air particle-bound trace metals in four selected communities in Ibadan, Nigeria.

ABSTRACT

Trace metal concentrations were determined in particulate matter (PM10) in ambient air of four purposively selected residential areas in Ibadan, Nigeria namely Bodija market (BM), Ojo Park (OP), Oluyole Estate (OE) and University of Ibadan (UI). PM10 was determined in the morning (7-10 a.m.) and afternoon (2-5 p.m.) for 12 weeks in the dry season months of January-March using a volumetric sampler following standard procedures and levels compared with WHO guideline limits. Glass-fibre filter papers exposed to the particulate matter were digested using appropriate acid mixtures, and the digest analysed for trace metals including Ni, Cr, Mn, Zn, and Pb using ICPMS method and levels compared with WHO limits. Data was analysed using ANOVA and Pearson correlation test at 5 % level of significance. The highest mean PM10 concentrations 502.3 ± 39.9 µg/m(3) were recorded in the afternoon period at BM, while the lowest concentration 220.6 ± 69.9 µg/m(3) was observed in the morning hours at UI. There was a significant difference between the PM10 levels across the various locations (p < 0.05), and all the levels were higher than WHO limit of 50 µg/m(3). The highest levels of Ni, Zn and Pb were recorded at BM, which also had the highest PM10 burden. The trend in Pb levels across the locations was BM > UI > OP > OE with the highest level 5.70 µg/m(3) in BM nearly fourfolds WHO limits of 1.5 µg/m(3). There was a significant correlation between PM10 and Ni (p < 0.05).Urban communities with increased human activities especially motor traffic recorded both higher levels of PM10 and toxic trace metals. There is need to carry out source apportionment to establish the origin of these trace metals in future studies.