Spatial Distribution and Bioaccumulation of Selected Heavy Metals by Pennisetum Purpureum Grown on an Abandoned Gold Mine Dump in Western Kenya

Abstract

Soils in gold mining areas are threatened by heavy metal contamination, posing a a great danger to the environment and to both animal and human health. This study was aimed assessing the uptake and bioaccumulation of Cu, Pb, Cd, and Zn, in Pennisetum purpureum grown on a gold mine dump in western Kenya. Soil and plant samples were randomly collected from four points on the mine dump in March 2024. The control samples were collected away from the mine dump. The samples were collected in triplicate and air-dried for two weeks. The plant samples were separated into the different parts, and with soil samples, they were each separately ground into fine powder. 50 g of each set of replicates was combined to form a composite sample. The samples were digested and the levels of the metals were determined using atomic absorption spectroscopy. The amount each metal in the samples from the mine dump was higher than the WHO permissible levels for agricultural soils and plants. The quantities of the heavy metals in the soil and plants were in the order Cd<Pb<Zn<Cu. The metal levels in the plants were, Cu: soil>roots>leaves>stem, Pb: soil>leaves>roots>stems, Cd: soil>stems>roots>leaves, and Zn: soil>roots>stems>leaves. Synergistic interactions were observed between the quantities of the different metals in the soils and in different plant parts. Although P. purpureum samples from the mine dump were contaminated by Pb, Cu, Zn, and Cd, hence unfit for livestock consumption, the crop has great potential for phytoremediation of the heavy metal in contaminated soil.