The study examined potential of agroforestry trees in phytoextraction of toxic heavy metals and metalloids (Pb, Cd, As and Hg) in soils from abandoned mine sites. The soil contained high levels of Pb (450 mg/ kg), Cd (25 mg/kg) and As (120 mg/kg). Three trees were planted in the contaminated soil: Eucalyptus camaldulensis, Acacia nilotica and Leucaena leucocephala, in a completely randomised block design with three replicates. After six months, tissue samples were collected and heavy metal concentrations analysed by graphite furnace atomic absorption spectroscopy (GFAAS) and atomic absorption spectroscopy (AAS). Results showed that L. leucocephala had the highest accumulation of Pb (145 mg/kg) and Cd (28 mg/kg) in roots, while A. nilotica had lower levels but still showed absorption capacity. E. camaldulensis showed potential for phytoextraction as it could translocate both heavy metals and metalloids to the topical tissues. Overall, all the three tree species demonstrated ability to remediate contaminated soils. L. leucocephala and A. nilotica had high phytoremediation capacity based on their phytoextraction efficiency and can be used to reclaim contaminated soils. However, further research is required to evaluate the time and frequency of tree planting over several cycles.
Parwada et al. (Fri,) studied this question.