PHYTOREMEDIATION OF HEAVY METALS IN THE POLLUTED SOIL AND HYDROPONIC SYSTEM USING SELECTED TROPICAL PLANT SPECIES

Abstract

Phytoremediation and phytoextraction processes have being in-used experimentally and in real-time operations for the uptake and recovery of metals and heavy metals from contaminated soils. The current study evaluates Celosia argentea, Corchorus olitorius, Amaranthus gangeticus, Euphorbia heterophylla for the phytoextraction of Cu, Zn, Cd, and Pb in soils and hydroponic system. The phytoextraction potentials, the strength of the plants to tolerate single and multiple heavy metals concentrations were determined with the addition of enhancement agents (EDTA). Physico-chemical parameters of the soils that include: pH, conductivity, Cation exchange capacity, soil texture, soil organic matter, and soil structure (Clay, Loamy and Silt), elemental and heavy metal properties were determined: K, Na, Pb, Cd, Zn, Cu, and Mg, all the parameters are within the allowable limits. The concentrations of the heavy metals taken from by all the plants were determined: For Cu, it ranged from (3.00 ± 0.2 mg/kg -.295 ± 4.3 mg/kg: For Zn, it ranges from (5.60 ± 1.2 mg/kg - 350 ± 5.0 mg/kg): For Cd, it ranged from (2.10±0.2 mg/kg - 155 ± 3.30 mg/kg): For Pb (4.6 ± 0.2 mg/kg - 135 ± 4.0 mg/kg). The plants extracted almost twice the concentrations taken from the soil experiments in hydroponic solutions The addition of enrichment agent (EDTA), proved effective in the phytoextraction of selected heavy metals. Sequential extraction results showed that the heavy metals available to the plants from the soils are majorly associated with the exchangeable fraction, Fe-Mn oxides fraction, and partly organic matter fraction. The physiological examination of Euphorbia hetrerophylla showed that it possesses milky sap latex, which may have helped in the bioaccumulation of heavy metals. Hydroponic experiments showed that Celosia argentea produces exudate on exposure to a higher concentration of heavy metals, which are difficult to extrapolate in soil potted, and field experiments. Under this study, the evaluation of these plants recommends; labeling Sunflower and Euphorbia heterophylla as heavy metals extractors, Corchorus olitorius as phytoextractor of lead exclusively and justified Celosia argentea as a toxic metal indicator plant