Objective: To determine the concentrations of heavy metals in soil and groundwater at municipal refuse
dumps in Ibadan, Nigeria, and make recommendations to improve refuse management.
Methodology and results: Soil and groundwater samples from 7 municipal refuse dumps and a green
uncontaminated control site at the Institute of Agricultural Research and Training in Ibadan, Nigeria were
analysed for Cadmium (Cd), Cobalt (Co), Lead (Pb), Chromium (Cr) and Nickel (Ni). Soil samples were
obtained in triplicates and at depths of 0-15, 15-30, 30-45 and 45-60cm. Water samples were obtained from
dug wells at the dump sites. The values of Cd, Co, Pb, Ni and Cr in the dumpsites soil samples ranged
from 0.75-16.30; 3.45-21.00; 45.00-624.50; 4.35-49.80 and 13.15-75.55mg/kg, respectively. Evidence of
contamination of these soils by Cd, Pb, Ni and Cr was obvious when compared to the control site. Ni was
below detection limit in all control samples while Pb and Cd were less than 0.05 and 0.002mg/kg,
respectively. Cr ranged from 6.25-19.75mg/kg. The range obtained for Co at the dumpsites was
comparable to that of the control soil which was 7.22-28.15mg/kg. Compared to established limits set for
soils in some countries, the values measured in this study were higher, particularly for Pb. Co conformed to
the only established limit cited in Austria. Values measured in the groundwater samples were lower than
the limits set by WHO for drinking water, except Cd which was detected in 3 of the samples at a
concentration close to the WHO limit.
Conclusion and application of findings: This study found that there is an ongoing build up of heavy metals in
soil at the waste dumps studied and concentrations were already higher than established limits for some
metals. The recommendations of the study include formulation and enforcement of a directive to prevent
any form of farming on the dumpsites, relocation of the dumpsites out of the city and the enforcement of
other environmental protection regulations to stop the ongoing buildup of these metals on those locations.
Findings from this study will be of immense help to researchers and environmental regulators in developing
countries.