Exploring the use of indigenous crops for heavy metal phytoremediation of mine contaminated soils

Thesis (M. Sc. (Soil Science)) -- University of Limpopo, 2024

Soil contamination with heavy metals poses a significant environmental risk and is one of the world’s most pressing issue. People's health and soil are being seriously harmed by heavy metal pollution in mining locations. A crop-based technique called phytoremediation employs plants to either extract and remove pollutants from the soil or lessen their availability. The objectives of this study were to determine whether the selected indigenous crops would decrease heavy metal concentration in mine polluted soils through phytoremediation; and to determine whether the growth of selected indigenous crops will be affected by phytoremediation. A pot study comprising of 5 treatments which were arranged in a randomized complete block design (RCBD), replicated 4 times was conducted at the Green Biotechnology Research Centre (GBRC). The treatments consisted of: Amaranthus hybridus (A), Cleome gyanandra (C1), Bidens pilosa (B), Cucumis africanus (C2) and control (C0). Soil samples used in the study were collected from Tikhontele farm in Barberton, Mpumalanga. Soil samples were also analysed at the Soil Science Laboratory at the University of Limpopo and Limpopo Agro-Food Technology Station (LATS) for soil physicochemical properties (soil texture, soil pH (H2O and KCl),electrical conductivity (EC), organic carbon (OC), soil phosphorus (P) and basic cations (Ca, K, Mg and Na)). Four non-essential heavy metals, Arsenic (As), Cadmium (Cd), Chromium (Cr) and Lead (Pb) were also extracted. Crop species used were analysed for growth parameters, leaf length, stem diameter, chlorophyll content and the number of leaves were counted weekly. Bioaccumulation factor (BAF) data was computed using Genstat 18. The results revealed that all the crop species were able to decrease the heavy metals from the mine contaminated soils, the control of the study also showed a decrease in the heavy metals except for Cd. The results show that Pb was the highest reduced heavy metal in the soil. Treatment effects were highly significant for Pb, significant for As and not significant for Cr and Cd. The BAF of the different crops for the different heavy metals was below 1. Furthermore, results showed that BAF was generally high for Pb and low for Cr. The study found that the growth of crops was not affected by mine contaminated soils during phytoremediation. These results confirmed that these crops species were effective phytostablisers of As, Cd, Cr and Pb.