The Potential of Indigenous Plants for Use in Phytoremediation of Tailings Dam at Chirano Gold Mine, Ghana

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The potential of indigenous plants for use in phytoremediation of heavy metal contaminated soil in Chirano Gold Mine Limited was investigated. Plant species growing in and around the Tailings Storage Facility 1 were sampled in five plots, randomly selected. Plants species diversity was determined using the Shannon-Weiner Index. Plants root and shoot of all identified species and soil samples were collected and analysed for Arsenic, Cadmium and Zinc concentrations using Atomic Absorption Spectrophotometer while for Cyanide concentration Cyanide Analyser (Flow-injection analysis) was used. Bioavailable fractions of studied metals were also measured with formation of metal complex with Ethylenediaminetetraacetic acid and ammonium acetate reagents. Data obtained were subjected to Analysis of Variance (ANOVA) using SPSS version 16 with values for p < 0.05 considered significantly different. The hyper-accumulation potential and mobility of heavy metals within the plants were determined from the bioaccumulation and translocation factors. A total of 19 plant species belonging to 8 families were identified. The most abundant family was Poaceae (37%). Grasses were the dominant growth form which contributed much to the Shannon-Weiner Index of 2.01. Majority of plants species (90%) are propagated by seeds. The total and bioavailable mean content of heavy metals (Zn, Cd and As) varied in the area with Zinc being most predominant-13.20±0.06 mg/kg. However, CN was the most bioavailable with percentage bioavailability of 64. The soil elemental concentrations of Zn (13.20 mg/kg), Cd (0.29 mg/kg), As (3.0 mg/kg) and CN (0.11 mg/kg) were below the WHO recommended standards of 200 mg/kg, 1.4 mg/kg, 12 mg/kg, and 0.9 mg/kg for Zn, Cd, As and CN respectively. The concentrations of all metals were significantly higher in the roots than in the shoots. In all plant species Zinc was the most accumulated heavy metal, recording the highest level of accumulation in the root of Euphorbia heterophylla. Bioaccumulation factor as expressed by total and bioavailable metal concentration in soil indicate that all the plant species demonstrate good hyperaccumulation and phytoextraction potential for Zn and Cd whilst 13 and 8 plant species demonstrate good accumulation and phytoextraction potential for CN and As, respectively. The translocation factor indicates that 8 plant species are good phytotranslocators for Zn, 7 plant species for Cd, 10 plant species for As and 8 plants species CN. The accumulative and phytotranslocation potential of these plant species provide useful information about theirs elective exploitation for effective phytoremediation of the tailings dam at Chirano Gold Mine.
A thesis submitted to the Department of Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirements Master of Science degree in Environmental Science, 2016