Heavy Metal Phytoremediation Potential of Wild Plant Species Naturally Growing on Dumpsite, Kenya

Abstract

Soils form an essential part of life and the main sink of pollutants. Intense industrial and anthropogenic activities have led to serious environmental threats, resulting in increased heavy metal concentration in soils and, consequently, a phytotoxicity effect on plants. Phytoremediation can offer effective and eco-friendly remedies for polluted sites. This study characterized the diversity of various plants that spontaneously grow in a dumpsite and scrutinized their phytoremediation potential. The plants evaluated for phytoremediation potential were Ricinus communis, Parthenium hysterophorus, Cassia didymobotrya, and Datura stramonium. The location of the research was Kang’oki dumpsite, Kenya. Species diversity was studied using quadrat sampling thrown randomly throughout the dump site. The bioaccumulation factor (BF) and the translocation factor (TF) were calculated to determine the accumulation and mobility of the heavy metals in the plants. To determine the ability of the plants to remove, accumulate, and mobilize the selected heavy metals, soil and plant sampling was conducted within the 14 sampling sites. The samples were acid-digested, and concentrations of Pb, Zn, Cu, and Cd were analyzed using Atomic Absorption spectrophotometry. Data obtained was subjected to statistical analysis using SAS version 94. Shannon-Weaver diversity index (H’) was used for species diversity. An H’ of 0.94 and species evenness of 0.45 was found showing a high species diversity on the dumpsite. Cadmium concentration in soil samples ranged from ND to 1.63 mg/kg of soils and 0.4418 to 0.6939 mg/kg of plant tissues. Nickel concentration ranged from 7.9 to 36.33 mg/kg in soils and 9.31 to 11.38 mg/kg in plant tissue, respectively. Copper was found between 3.41 to 121.18 mg/kg of soils and 3.74 to 10.89 mg/kg of plant tissues, respectively. Lead in soils ranged from 13.25 to 8.013 mg/kg of soils and 11.48 to 13.89 of plant tissues. Leaves accumulated significantly (p < 0.05) higher amounts of heavy metals than roots and stems. The leaves and stem of Datura stramonium showed the highest concentration of cadmium and copper, while its stem showed the maximum concentration of Nickel and lead. Datura stramonium showed BCF and TF >1; hence, it can be used for phytoextraction of cadmium. All plants showed TF>1; hence, these plants can be used as hyperaccumulators.