Assessment of Heavy Metal Levels in the Soils of Ohyia Kaolin Mining Site and Screening of Three Local Herbaceous Species for Use in Phytoremediation

Abstract

The study assessed three local plant species Chromolaena odorata, Ipomoea involucrata and Mariscus alternifolius commonly found at abandoned  kaolin mining site at Ohiya, Umuahia Abia state for their efficacy in phyto-remediation of heavy metals contaminated soil using a pot experiment. Soils from Ohiya kaolin mining site were used as medium for growing the species. Pre-experiment assessments of the concentrations of six heavy metals (Cr, Pb, Ni, Cd, Co and Se) were carried out in the soil and plant tissues to be used for the experiment. The experiment was laid out in a Randomized Complete Block Design (RCBD) with 6 replicate pots each. The physico-chemical properties of the experimental soil showed high content of lead (Pb) and cobalt (Co) contamination which were (2.40mg/kg) and (9.84mg/kg) respectively. Post-trial plant analysis revealed that the three plant species used for the study accumulated appreciable quantities of the heavy metals. The ranges of Pb in the species were as follows C. odorata (0.80-1.00mg/kg), I. involucrata (1.00-2.00mg/kg), M. alternifolius (0.40-0.70mg/kg). The ranges of Cr were: C. odorata from (0.00-0.07mg/kg), I. involucrata (0.30-0.42mg/kg), M. alternifolius (0.01-0.10mg/kg).  The ranges of Cd in the species were: C. odorata (0.02-0.30mg/kg), I. involucrata (0.10-0.70mg/kg), M. alternifolius (0.10-0.60mg/kg) and Co concentrations were: C. odorata (2.00-3.07mg/kg), I. involucrata (2.01-4.01mg/kg), M. alternifolius (2.01-2.10mg/k). Ipomoea involucrata had significantly higher accumulation of Pb and Co than the two other plant species used and should be preferred in phytoremediation activities in the kaolin mine site at Ohiya or soils with high concentrations of heavy metals.