SUITMA 2005 Cairo - Trends of heavy metals contamination in urban soils: a scenario from Ibadan metropolis, S.W. Nigeria
SUITMA 2005 Cairo
| This abstract is about one of the papers of the Properties of unconventional soils theme of the SUITMA 2005 symposium. |
| Moshood Tijani,i | Akinlolu F. Abimbola,i |
| Olugbenga A. Okunlola.i |
- i - Department of Geology, University of Ibadan, Ibadan, Nigeria.
Intensive urbanization due to rapid population increase and rural-urban migration had resulted in varied human activities and uncoordinated land use planning within the urban catchment of Ibadan metropolis, SW, Nigeria. Hence, environmental contamination assessment of surface soil samples from different soil categories covering road-sides, farmlands, industrial sites, residential areas, waste-dump sites and mechanic workshops/ motor parks soils were undertaken with respect to influence of urbanized catchment on trace/ heavy metals contaminations. The total concentrations of 10 trace/heavy metals in 35 soil samples were analyzed using XRF. The results show average total concentrations of 42.5g/kg Fe, 1.1g/kg Mn, 84.6mg/kg Cu, 224.6mg/kg Pb, 526.2mg/kg Zn, 32.4mg/kg Ni, 90.1mg/kg Cr, 21.9mg/kg Co, 95.1mg/kg V and 8.3mg/kg. The trace metals (Fe, Mn, Cu, Pb, Zn, Ni, Cr, Co, V and Sc) vary from 0.01 to 0.5mg/l. However, with the exception of Cr, which exhibits concentration similar to the local background concentrations (LBC) within the granitic catchment area, all other analyzed metals revealed 2–6 folds enrichment suggesting anthropogenic metal inputs.
Multivariate statistical analysis involving R-mode factor analysis employed revealed two dominant groupings; F1, which loaded in favor of Sc, Ni, V, Cr, Co and partly Fe and Mn, indicates dominant weathering-pedogenetic influence, while F2 with Cu, Pb, Zn and partly Mn signifies strong anthropogenic influence. This is clearly consistent with the estimated index of geo-accumulation (Igeo) of 1.5 – 3.5 and Al-normalized enrichment factor (EF) of 2.0 – 16.6 for Cu, Pb and Zn indicating moderate to high contamination level. Furthermore, the estimated total metal contamination index (MCI) of 25 for peri-urban virgin soils suggests minimal or no indication of anthropogenic metal inputs, while higher MCI values of 40 (for industrial sites, mechanic workshops/motor parks), 45 (for roadside and farmland soils) and 60 (for waste-dump sites soils) indicate high to very high contamination level. Although, metal contaminations are attributable to varied human activities within the study area, the relatively small variations between the estimated contamination indices for the different soils categories could be attributed to significant or dominant contribution of diffuse traffic emissions and other air-borne related particulate emission sources. Finally, highlights of environmental significance of the observed metal contamination in respect of the urbanization impacts (and associated anthropogenic activities) as well as poor/inadequate infrastructural and land-use plans characteristics of most urban centers of developing countries are also presented.
Nonetheless, the relative enrichment in the soils over the geogenic background concentrations imply potential bioavailable contamination source in terms of possible remobilization into the surface water and stream sediments by erosional wash-out as well as plant uptake and possible transfer into higher tropic level.
