Assessment of Tithonia Diversifolia With Mycorrhizal Bioaugmentation in Phytoremediation of Lead and Zinc Polluted Soils

Abstract

Human activities cause soil contamination with heavy metals, with a negative impact on plant growth and productivity, and consequently animal and human health. Phytoremediation, a cost effective and eco-friendly remediation technique, requires fast growing large biomass plants naturally found in polluted soil. This research assessed the potential of Tithonia diversifolia with arbuscular mycorrhiza (AM) bio-augmentation in phytoremediation of heavy metal polluted soil. T. diversifolia seedlings were raised in potted soil contaminated with lead (PbSO4) or zinc (ZnSO₄) in separate experiments at 0, 20, 40, 60, 80 and 100 mg/kg. The potted soils were divided into two groups; the first group contained Pb/Zn contaminated potted soils with 5 g of AM fungus (Glomus clarum) each while the second group made up of potted soils with Pb/Zn contamination each without AM inoculation. Growth and biomass production reduced in Pb and Zn contaminated soils with/without AM, compared to the control. Heavy metal contamination decreased the number of leaves, plant height, stem girth, leaf area, fresh/dry mass of plant parts and total biomass, with variations depending on metal type, concentration applied, parameter determined and soil status (presence or absence of AM). Metal contamination led to more Pb and Zn contents in plant tissues than the control. Soil with AM caused increased plant metal content than those without it. More Zn was accumulated than Pb with a higher quantity of Pb in the root than shoot with/without AM while Zn was more in the shoot than root under AM inoculation and vice versa without it. Tithonia diversifolia is recommended for phytoremediation of Pb and Zn polluted soil, and bio-augmentation with Glomus clarum will bring about better performance.