Environment, health and risk assessment: A case study of the use of an abandoned municipal waste dump site for agricultural purposes

Abstract

The study was carried out on abandoned municipal waste dump site which has been converted to agricultural land. Three profile pits each of 100 cm depth were dug along a toposequence on the land. The profile pit P1 was dug on the crest while P2 and P3 were on the middle and down slope (valley
bottom), respectively. Soil samples were collected at 10 cm interval from each profile and cassava (Mannihot esculenta Cranz) and cocoyam (Colocesia esculenta) were selected at random and harvested from the whole farm. Heavy metal content (Pb, Ni, Cd, Cu and Zn) of soils and the crops (roots and leaves) were determined. The level of Pb was found to be highest in both soils and food crops with the total mean concentration of 133.74±10.60 mg/kg in soil. The Pb level was 83.02±27.84 and 105.37±45.37 mg/kg in the roots and leaves of cocoyam, respectively, and 76.6±19.94 and 111.51±17.78 mg/kg in the roots and leaves of cassava, respectively. Cadmium had the least mean concentration in both soil and
food crops with 2.08±0.12 mg/kg in soil and 4.10 in the roots and leaves of both cassava and cocoyam. When the individual profile pits were examined, no regular variation of heavy metal was observed but there was tendency of accumulation of heavy metal in soils of down slope P3 because it had the
highest mean concentration of all the heavy metal except for Zn. Correlation analysis was used to examine the dependency of the heavy metals upon themselves, Cu and Zn had positive correlation with
Pb, Cd with Zn, and Zn with Cu.