Effect Of Edta, Dtpa And Ph On Cadmium Uptake By Water Hyacinth From Contaminated Sediment
Chelating agents and pH play a significant role in affecting heavy metal availability from contaminated sediment. Eichhorniacrassipes (water hyacinth) were studied for efficiency of cadmium (Cd) uptake using Ethylenediaminetetraacetic acid (EDTA), Diethylenetriaminepentaacetic acid (DTPA), and a mixture of EDTA-DTPA (EDTA/DTPA) at various pH. Experiments were conducted by adding 2 mg/L of EDTA, DTPA, and EDTA/DTPA at pH 4, 5, 7, and 9. Plants were submerged in water containing 80 mg/kg of Cd contaminated sediment and harvested at 30, 60, 90, and 120 days in order to measure Cd concentrations in two parts, including the shoots (stems and leaves) and roots. The results showed that Cd accumulation in plants with added EDTA and DTPA was higher than in control sets, indicating that EDTA and DTPA enhanced Cd uptake by water hyacinth. However, the results of overall pH from EDTA and DTPA were not significantly different on Cd uptake. The Cd concentrations in roots from EDTA and DTPA were 62.53 and 61.17 mg/kg, respectively. Shoots can accumulate Cd in lower levels than in roots by approximately 10 times compared to roots for both EDTA and DTPA. Cd accumulations in roots were significantly (P<0.05) higher than in shoots. For EDTA/DTPA treatment, average Cd accumulation in roots (112.7 mg/kg) was higher than in shoots (14.23 mg/kg) at 90 days. The appropriate conditions for reducing Cd concentrations in contaminated sediment by uptake of Cd in water hyacinth are synergistic mechanism of EDTA/DTPA at pH 5, which provides Cd removal capacity from sediment more than 0.51% within 3 months. This may imply that the higher level of Cd uptake by EDTA/DTPA mixture is due to the concentrations of chelating agent.
Keywords - Cadmium, EDTA, DTPA, Water hyacinth, Phytoremediation