Changes in soil properties and plant uptake of heavy metals on selected municipal solid waste dump sites in Ile-Ife, Nigeria
In a study to evaluate the contributions of open municipal waste dump to soil heavy metals contamination and the modification of other soil physical and chemical parameters, soil samples were collected at various depths from the vicinity of major dump sites in Ile-Ife (latitudes 7°27' and 7°32', longitudes 4° 22' and 4° 29'), Nigeria. The samples when analyzed, showed that soils in the vicinity of dump sites had significantly higher pH regime compared to the control soil. Soils of the dump sites were found to be enriched with the heavy metals (Zn, Cu and Cd) more than the adjacent soils (control) but were still within tolerable /critical level with the exception of Pb which had a high value of 109.7 ugg-1 above the critical value of 100 ugg-1. There was significant relationship between the soil heavy metal content and plant uptake. Transfer factor (TF) expressed as the ratio of the heavy metal concentration in plants to that of soil varied significantly amongst the dump sites and also amongst the species of the heavy metals. The ten years old dump sites recorded the highest TF value ranging from 0.29 for Zn to 4.05 for Pb. The study therefore showed that changes in physico-chemical characteristics at dump sites could be attributed to interactions of different soil properties rather a single factor.
Key words: Heavy metal contamination, seasonal changes, soil pH, soil texture, specific adsorption mechanism, transfer factor, food chain.