Phytoremediation Potential of Cyperus Rotundus L. in Soils Contaminated with Potentially Toxic Elements, the Case of Abandoned Artisanal Small-Scale Gold Mines in Kenya

Abstract

Phytoremediation involves the use of plants for removal of pollutants from soil before its conversion for agricultural use. Cyperus rotundus L. is a reed that naturally grows in marshy and swampy areas including abandoned artisanal small-scale gold mines. This study was aimed at determining the potential of C. rotundus reeds for removal of Cu, Pb and Cd from soil polluted by artisanal small-scale gold mining (ASGM) activities in in western Kenya. C. rotundus plant and soil samples were collected in triplicate from five randomly selected localities where ASGM is practiced in western Kenya. The control samples were sourced from a locality where ASGM operations have never been conducted. After washing and separating the plants samples into leaves and roots, both soil and plant samples were air dried, oven dried and milled to fine powder. The replicate samples from each locality were combined to form a composite sample which was then digested and the levels of Cu, Pb and Cd, determined using an atomic absorption spectrophotometer in triplicate. Data analysis was done using Microsoft Excel version 2013. The levels of Pb, Cu and Cd, in the samples from the abandoned mines were higher than those of control samples. The levels of metals in the soil samples collected from the mines were in the order Cu>Pb>Cd. Quantities of the metals in the soil, root and leaf samples were in the order root>soil>leaf for Pb and Cd, while for Cu, it was roots>leaves>soil. The BCF values for C. rotundus roots and leaves of the different metals were in the order Cu>Pb>Cd and Cu>Cd>Pb respectively. The TF values for Cu (0.85±0.01 – 0.99±0.03) were highest followed Cd (0.42±0.03 – 0.86±0.03) and lowest for Pb (0.31±0.03 – 0.80±0.01). The MAI values were in the range 66.6-101. Uptake of Cu by the plant results in increased uptake of Pb but decreased uptake of Cd from the soil, while the uptake of Pb is not affected by availability of Cd in the soil and root tissues. Phytoremediation of Cu, Pb and Cd from soil polluted ASGM activities using C. rotundus is an environmentally friendly and cost-effective method of reduction of heavy metal toxicity in the soil.