Phytoextraction of cadmium from petroleum contaminated soil by Vigna subterranean

By Nwaichi, O. Eucharia and Wegwu, O. Mathew

Abstract

Pot experiments were carried out to investigate cadmium (Cd) uptake and accumulation by Vigna subterranean from soil artificially spiked with Nigerian Bonny light crude oil (up to 100mL/2kg soil). Effects of amendments such as poultry manure, NPK and UREA fertilizers on phytoextraction were also investigated. Cd uptake levels of 108.97mg kg-1 and 56.25mg kg-1 for the shoots and roots, respectively within 12 weeks of study, giving a shoot: root quotient of 1.94 at the highest contaminant dose, were observed. Shoot and root Cd concentrations increased linearly with increasing contaminant dose with or without amendments except for UREA that peaked at 8% contamination. Cadmium uptake by shoots were 101.48, 101.68, 101.75, 108.83 and 108.97 mg kg-1 at 2, 4, 6, 8 and 10% (w/v) contamination, respectively suggesting that additional cadmium removal could be achieved by successive revegetation over a growing period. Amendments generally improved Cd phytoavailabilty, thus the levels found in tissues. There was no significant difference between the plant’s performance under stress in the nutrient un-amended and amended treatments except at the highest dose of contaminant in the poultry manure amended regime. The results indicate that V. subterranean is a Cd hyperaccumulator with a high capacity to accumulate Cd in the shoots.

 

Key Words : Vigna subterranean; Contamination; cadmium extraction; shoot: root quotient (SRQ); Amendments.

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