ASSESSMENT OF HEAVY METAL POLLUTION IN THE URBAN SOILS OF SOME PARTS OF SOUTHWESTERN NIGERIA

Globally, urban soils are highly polluted with heavy metals arising from anthropogenic and geogenic sources. The objective of this study was to investigate the pollution and their sources in the urban soils of Ago Iwoye and Ijebu Ode, Southwestern Nigeria. Soil samples collected were analysed for heavy metal concentration using inductively coupled plasma mass spectrophotometer (ICP-MS) at ACME laboratories, Ontario Canada.

The results indicated that (1) All the soil samples investigated have been polluted to varying degrees with lead, cadmium, copper, zinc silver, nickel, cobalt, tin and vanadium which suggest high anthropogenic influences; (2) Only few soil samples from Ijebu ode have been polluted by molybdenum. (3) Few samples from Ago Iwoye showed low concentration of yttrium and zirconium.

The degree of pollution for trace elements was assessed using enrichment factor, contamination factor and degree, geo-accumulation index and pollution load index.

The results showed minimum to significant enrichment of Ago Iwoye and Ijebu Ode soils by Ag, Pb, Zn, Cd, Sn, Cu and Pb, Zn, Ag, Cd, Sn, Sr respectively. Pollution Load Index (PLI) was above 1 for all the study areas and this confirmed soil contamination. Pb was mostly responsible for the contamination recorded in all the study areas.

The calculated contamination degree for Ago Iwoye and Ijebu Ode soils were 23.47 and 26.57respectively which indicate considerable degree of contamination for the two sites.

The sources of these metals are mostly from vehicular and industrial emissions typical of urban areas.