The Effect of Humic and Fulvic Acids on Phytoremediation Ability of Copper and Cadmium by Ornamental Castor Bean

It is essential to use of an inexpensive and eco-friendly method to reduce the environmental hazards of heavy metals. In this study, the effect of humic acid (HA) and fulvic acids (FA) on the availability of copper and cadmium and their uptake by ornamental castor oil was investigated in the greenhouse of Shahid Bahonar University of Kerman. Treatments including two levels of HA and FA (0.5 and 1 %) were added to a Cu-Cd polluted soil with five replications. A treatment received no organic acid as a control. After 90 days, some plant growth characteristics, available Cu and Cd and shoot, and root Cu, Cd concentration were measured. The results showed that application of 0.5% of humic acid to soil increased the growth characteristics of ornamental castor. In contrast, the addition of humic acid at the rate of 1% and fulvic acid at the rate of 0.5 and 1% significantly reduced plant growth characteristics. Soil application of 0.5 and 1% of humic acid increased available Cu by 19 and 37% and available Cd by 30 and 44%, respectively. Available Cu and Cd in soils treated with 0.5 and 1% of fulvic acid were 35 and 39%, and 42 and 54% higher than the control. Shoot and root Cu and Cd concentration were significantly increased in plants treated with 0.5 and 1% of humic and fulvic acids. Bioaccumulation and translocation factors were less than 1 in all treatments and increased in soil treated with 1 % of HA and FA. Based on these results, ornamental castor been could not be considered as a hyperaccumulator plants. However, humic and fulvic acids can increase the phytoremediation ability of ornamental castor for Cu and Cd removal.