Chemical fractionation and plant uptake of heavy metals in chromated copper arsenate (cca) contaminated soil amended with ethylenediamine tetraacetic acid (edta)

Abstract

Contamination of soils by heavy metals is of considerable concern with respect to heath risk, phytotoxity, long term effects on soil fertility and depreciation of land. Of particular concern is the widespread low-to-medium levels of pollution of agricultural and cultivated land and land with high environmental sensitivity index, for which conventional physicochemical methods of remediation are generally unsuitable. Innovative technologies, such as phytoremediation, has been proposed as low-cost, ecofriendly, less-intensive remediation technique for soils contaminated with heavy metals. This study examined the phytoextraction capacity of maize plant for As, Cr and Cu in CCA contaminated soil amended with EDTA. Maize seedlings grown on CCA contaminated soil (MTotal 426.0 mg.kg-1, As 31.70 mg.kg-1, Cr 24.1 mg.kg-1 and Cu 152.9 mg.kg-1) samples were treated with 100ml of EDTA solutions (0, 20, 40, 60, 80 and 100mM) 15 days after germination. The maize plants were harvested 5days after EDTA application and the levels of As, Cr and Cu in the roots and shoots of the plant were determined by Atomic Absorption Spectrophotometry (AAS). It was found that EDTA application markedly enhanced As, Cr and Cu extraction by maize, with transfer constants and translocation factors of metals in the amended soil several orders of magnitude higher than the corresponding values in unamended soil. A mathematical model was proposed to show the relationship between the amount of the metal mobilized from the contaminated soil matrix following EDTA application with plant uptake parameters and indices