Phytoremediation potential of indigenous plants at Nchanga mine,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. Phytoremediation is a cost effective technology that involves the efficient use of plants to eliminate or immobilize environmental contaminants. 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 research investigated the phytoremediation potential of indigenous plants growing at the tailings dams of Nchanga Mine in Chingola, Zambia. Tailings Dam Four (TD4) and a site 50m away from TD4 at Nchanga Mine were sampled. TD4 and Sampling Area Two were divided into four and two quadrats, respectively. Each quadrat was further divided into nine plots and three plots from each quadrat were randomly sampled. Composite soil samples were collected from the plots and a total of 175 individuals of 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. Arthraxon quartinianus (A. Rich.) Nash.(a grass specie) had the highest concentration of Cu (1016.8 mg/kg) while Cyperus rotundus L. (a grass specie)had the lowest (29.35 mg/kg). Arthraxon quartinianus (A. Rich.) Nash.had the highest concentration of Zn (192.8 mg/kg) and Crinum L. (a herb)had the lowest (28.24 mg/kg). The Bioaccumulation Factors indicated that all the plant species studied are Cu excluders; and with the exception of Crinum L., all were Zn accumulators and Arthraxon quartinianus (A. Rich.) Nash.was ahyperaccumulator of Zn. Results showed that all the plant species studied had potential for phytoremediation and can therefore be used in management and possible decontamination of mine dumps and areas surrounding the mines. Further research is needed to cover other heavy metals such as Cobalt, Nickel and Cadmium.