Effect of EDTA and DTPA on cadmium removal from contaminated soil with Eichhornia crassipes (water hyacinth)

Abstract

The effects of ethylenediaminetetraacetic acid (EDTA) and diethylene triaminepentaacetic acid (DTPA) on cadmium (Cd) uptake by water hyacinth (Eichhornia crassipes) in Cd contaminated soil were studied. The experimental design was separated into 2 parts: preliminary study and experimental procedure. The preliminary study investigated the using EDTA and DTPA at doses of 0, 0.5, 1, 2, 5, 10 and 20 mg/L, for 15, 30, 45 and 60 days. The results showed that water hyacinth grew well and did not show phytotoxicity under the various applications of EDTA and DTPA. The addition of EDTA and DTPA in higher concentrations did causenegative effects on the relative growth rate of water hyacinth. For the experimental procedure samples were separated into 4 groups: 1) contaminated soil 5 kg without chelating agent (Control), 2) contaminated soil 5 kg with EDTA added at concentrations of 0.5, 1 and 2 mg/L, 3) contaminated soil 5 kg with DTPA added at concentration of 0.5, 1 and 2 mg/L, and 4) contaminated soil 5 kg with a mixture of EDTA and DTPA (1:1) at 3 doses of 0.25, 0.5 and 1 mg/L. Plants were harvested at 20, 40, 60, 80 and 100 days. Cd levels were measured in the soil samples, water samples and two parts of the plant: shoot (stem and leaves) and root. The results showed that Cd accumulation in the root in all groups were significantly (P<0.05) higher than that in the shoot. Cd accumulation in plants with added EDTA and DTPA were higher than the control set, which indicates that EDTA and DTPA addition increased Cd uptake by water hyacinth. In EDTA added sets, the Cd accumulation in root was higher than shoots and were measured at 160.91 and 13.37 mg/kg at 100 days, respectively. For DTPA sets, the Cd accumulation in roots was also higher than shoots. At the DTPA concentration of 2 mg/l (ppm) and after 100 days of growing time Cd accumulation was 231.78 in root and 16.34 for shoots mg/kg dry weight of plant. For the mixture of both EDTA and DTPA sets, the Cd accumulation in roots was again higher than shoots. The EDTA and DTPA concentration of 2 mg/l (ppm) after 100 days of growing time showed the highest accumulation in roots at 157.48 and after 60 days of growing time showed the highest accumulation in shoots at 23.61 mg/kg dry weight of plant, Our conclusion in this research is that DTPA alone positively effected Cd uptakeby water hyacinth more so than EDTA only and the mixture of EDTA and DTPA.