The bioaccumulation factor (BF) values of metals uptake by plant(Kenaf) during the four-week experiment are shown in Fig. 3. The lowest BF value (0.11) was observed for Mn in the 1:1 compost/soil treatment while the highest BF value was found for Zn in the 1:3and 1:4 compost/soil treatments. It appears that compost/soil mixture has no significant effects on Cu and Zn bio-accumulated by Kenaf plant. The values of BF for Cu and Zn were not differentfrom each other in all the experimental pots. For other metals, BF values increased in the compost/soil mixture treatments 1:1–1:4 indicating high transfer of metals to Kenaf plant with decreasing compost content in soil [54]. This observation may be explained by the influence of compost on soil properties such as organic matter and pH [20]. These factors could affect metals solubility, mobility and bioavailability in soil [55].
Bioaccumulation factor values of metals in Kenaf plant were generally less than 1.0 indicating low metal uptake, and hence low environmental risks. The BF values of metals in Kenaf plant were low despite compost amendment. However, the plant was able to effectively remediate appreciable amounts of metals to establish its phytoremediation ability. The use of Kenaf plant for phytoremediation has been described in literature [56,57].
In the phytoremediation study conducted by Shrivastava [58], Brassica juncea was used to bioremediate Cd and Ni in industrial and urban polluted soils in Bhopa, India. High BF values of 10.5 and 1.3 were observed indicating high removal of metal by the plant used for phytoremediation.