ABSTRACT

Kaolin mining activities have been going on in Ohiya Community in Abia state since the 1990's. Undoubtedly, it has improved the economic wellbeing of the local people through employment. The impact of mining activities on both biotic and abiotic components of the environment has been a major source of public outcry for decades. This study assessed the kaolin mining generating heavy metal contamination in the mined area and screened three different local plant species for phyto-remediation. A preliminary assessment ofthe overburden indicated high levels of lead (Pb) and cobalt (Co) in the kaolin mined soil. Three local plant species Chromolaena odorata, Ipomoea involucrata and Mariscus alternifolius commonly A found at abandoned kaolin mining site at Ohiya were screened for efficacy in phytoremediation 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 ofsix 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 and growth parameters (plant height in (cm) was measured with tape and number of leaves was counted at monthly intervals).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 and also deficiency in macro elements (N P K). N ranges from (1.30- 3.00g), P (0.03- 0.09g.), K (0.49- 1.48g). The kaolin mined soil significantly affected all the growth parameters measured during the study. Post-trial plant analysis revealed that the three plant species used for the study accumulated appreciable quantities ofthe 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.lOmg/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 ofheavy metals.

Keywords: Phytoremediation, Heavy metals, Chromolaena odorata, Mariscus altamfolius, Ipomea. involuculata, soil, mining, and kaolin