The evaluation of the macrophyte species in the accumulation of selected elements from the Varkenslaagte drainage line in the west Wits, Johannesburg South Africa

Mthombeni, Tinyiko Salome
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Mining and associated anthropogenic activities have improved the livelihoods and economy of many countries but negatively impacted the environment and caused detrimental effects on fresh and ground water systems through the generation of acid mine drainage (AMD). The study evaluated three macrophyte species of P. communis, S.corymbosus and T. capensis for uptake of Mg, P, S, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, and Pb in acid mine drainage polluted water. The concentration of elements was also determined in sediments and water so as to calculate the bioconcentration and translocation factors in various parts of the macrophtes. The homogenised plant samples were milled using a Fritsch Pulverisette 6 Mill into pulverized powder and element analysis was done using Spectroscout Geo+ XRF Analyzer Pro. Sediment samples were digested with microwave assisted extraction and analysed by inductively coupled plasma optical emission spectrometry (ICP-OES). Water samples were analysed directly using ICP-OES after filteration with ICP-OES. The concentration levels of these elements in water were compared in all the sites to determine which section of the site (inflow, midflow and outflow) have high amount of the selected elements. The results indicated that elements distribution varied in all the points where the water samples were collected. The concentration level of sediment was compared to the concentration levels of elements in the roots, rhizomes and leaves to determine the translocation and bio concentration factor (TC and BCF). Drinking water quality standards by international organisations were also used as a guideline to compare the concentration levels of elements found in water. Iron (Fe), Nickel (Ni), Manganese (Mn) and Copper (Cu) to determine whether their concentrations in the water were above or below the acceptable levels. the concentrations of Fe, Ni, Mn and Cu were found to be above the international water quality standards for drinking water and their average concentrations was 2230, 282, 5950 and 14080 μg/l respectively. The study found out that in autumn, Mg, S, P, and Mo were highly accumulated by leaves of T. capensis, S. Corymbosus leaves and rhizomes as well as the P. communis leaves and the highest concentrations were 6.61, 72900, 2.00 μg/g respectively. In autumn, Co was the only element highly accumulated by the roots of T. capensis with the highest concentration of 342.80 μg/g. On the other hand, Cr and Fe, was highly accumulated by S. corymbosus roots with the highest concentration of 279.20 and 10.03 μg/g in summer. In summer, Cr, Mn, Ni, Cu, Zn and Pb were highly accumulated by the roots of P. communis and the concentrations were 279.20, 39390, 204.10, 299.50, 813.80 and 47.5 μg/g respectively. The results show that although the plant species accumulated the elements in various concentrations, there was no plant species that accumulated all the selected elements in higher concentrations than the other plant species. They all accumulated a variety of elements in varying amounts and stored them in their different parts. Finally, in all the three plant species analysed, the leaves were the best accumulator of Mg, S, and Mo, whilst the roots were the best accumulators of Cr, Fe, Co, Ni, Cu, Zn and Pb. Since the translocation and bioconcentration factors showed that the macrophyte species accumulated higher concentrations of elements than water and sediments, they can be regarded as hyperaccumulators. Macrophytes species can uptake and accumulate in their different parts various elements and they have the potential to clean the heavy metal polluted sites due to their phytostabilisation and phytoextraction abilities.
A research report submitted to the Faculty of Science, in partial fulfilment of the requirements for the degree of Master of Science, University of the Witwatersrand. Johannesburg, 2016.
Mthombeni, Tinyiko Salome (2016) The evaluation of the macrophyte species in the accumulation of selected elements from the Varkenslaagte drainage line in the west Wits, Johannesburg South Africa, University of Witwatersrand, Johannesburg, <