Phytoremediation Potential of Indigenous Plants Growing at Nchanga Mine in Chingola, Zambia

Abstract

Mining and smelting processes are among the key sources of soil contamination by heavy metals resulting in dramatic disturbances and loss of biodiversity. Native plants growing naturally in hostile mining environments can be used for management, decontamination and possible rehabilitation of polluted soils. These plants are either excluders or accumulators based on their Bioaccumulation Factors (BAF). This, therefore requires identification of native plants that are able to accumulate heavy metals in their plant tissues at concentrations higher than that in the soil in which they are growing. This study investigated the phytoremediation potential of indigenous plants growing at the tailings dams of Nchanga Mine in Chingola, Zambia. TD4 and a site 50 m away from TD4 were sampled as Sampling Areas One (1) and Two (2), respectively. TD4 was divided into four quadrants and three plots from each quadrant were randomly sampled. Three plots from each of the two quadrants from Sampling Area Two were also sampled. Composite soil samples were collected from the plots and a total of 175 individuals of 16 grass and herbaceous plant species were collected and analysed. Atomic Absorption Spectrophotometry was used to determine the concentrations of Copper (Cu) and Zinc (Zn) in the soils and plant specimens. The findings of the study showed that the concentrations of Cu and Zn in the soil ranged from 891.41 mg/kg to 15,617.47 mg/kg and 20.73 mg/kg to 96.85 mg/kg, respectively. Arthraxonquartinianus had the highest concentration of Cu (1016.8 mg/kg) while Cyperusrotundus had the lowest (29.35 mg/kg). Arthraxonquartinianus had the highest concentration of Zn (192.8 mg/kg) and Crinum had the lowest (28.24 mg/kg). BAF values for Cu were less than 1 in all the plants and BAF values for Zn were highest in Arthraxonquartinianus (10.77) with Crinum having the lowest BAF of 0.01. The Bioaccumulation Factors indicated that all the plant species studied are Cu excluders; and with the exception of Crinum , all were Zn accumulators and Arthraxonquartinianus , a hyperaccumulator of Zn.