Heavy Metal Contents in Soil and Plants at Dumpsites: A Case Study of Awotan and Ajakanga Dumpsite Ibadan, Oyo State, Nigeria

Abstract

This study investigates the heavy metal contents in soils and plants at Awotan and Ajakanga dumpsites in Ibadan with a particular reference to physiochemical and heavy metal levels of the underlying soils, the relationship between the dumpsite soil metal content and the rate of bio-accumulation by plants. A systematic sampling of twelve (12) soils sample (four per site) of twenty meters (20m)  interval and forty eight (48) dominant plants/ vegetable species were collected, uprooted from sample plot from Awotan and Ajakanga dumpsites and Idi-Ose farm land area which serve as control site of 20m. The soil samples were collected at each plot using clean stainless steel shovel at the depth of 0-30cm. The level of heavy metals (As, Cd, Co, Cu, Fe, Ni, Pb, and Zn) in soils, plants and vegetables from dumpsites and control site were determined using digestion and Atomic Absorption Spectrophotometer method (AAS). The transfer factor (Tf) revealed that plants grown on dumpsite soils by accumulated higher metal concentration than their counter part obtained from normal agricultural soil (control site). Generally, the result shows that there was an increase in the concentration of heavy metals in the two dumpsite soils than that of the soils at the control sites. The heavy metal (Fe and Zn) contents in the plants were higher at the two (2) dumpsites than control sites while the concentrations of Pb and Cd in the plants were higher at the dumpsite than control site. The level of heavy metals transfer for site A was in the order: Cu> Cd> As> Fe> Co> Pb> Zn> Ni while for site B was Cd > Cu > Fe > Co > As > Pb > Ni > Zn. Therefore, solid waste dumpsites contained high concentrations of heavy metals which are later absorbed and accumulated by the plants growing within such sites.

Keywords: Physiochemical, heavy metal level, Transfer factor and concentration.