The effect of EDTA and ammonium molybdate on increasing bioavailability efficiency and decreasing lead tension by corn

Introduction Industrial pollutants entering into the soil leads to the accumulation of excessive heavy metals such as lead, cadmium, copper and zinc in the soil. Phytoremediation is a method to remove heavy metals from the soil. Phytoremediation is one of the most important methods and technologies has been developed during the last two decades to solve the problem of metal pollution in different countries, Where the cultivated plants to clean, absorb and remove contaminants from the soil is presented. The chemical reaction of metals in soil is one of the key issues in the discussion of phytoremediation of heavy metals so in phytoremediation using chemical and organic substances increase the solubility of contaminants and in this way to improve the efficiency of the refining of pollutants by plants. Add chelating agents can increase the efficiency of metal uptake by plants. Soil application of chelating agents Such as Ethylene diamine tetra-acetic acid, increased the concentration of metals Such as lead in plants through increased solubility of metal and increased transfer it from the roots to stems. Ammonium molybdate has the ability and potential to precipitate Pb and Zn and reduces the toxicity of these metals in the plant. Ammonium molybdate has ability to producing chelate to form more soluble sections with Cd, Cu and Ni, this feature increases the bioavailability of these metals to the plant. The objectives of this study are evaluation of the effects of ammonium molybdate to increase the bioavailability of lead in corn plant and compare it with Ethylene diamine tetra-acetic acid for the removal of contaminants from the soil. Materials and Methods For this experiment was conducted in a completely randomized design with factorial arrangement with three replications in greenhouse of Agriculture and Natural Resources Research Center of Kerman province, Iran. Experimental factors included four levels of lead (zero (Pb0), 150 (Pb1), 300 (Pb2) and 450 (Pb3) milligrams of lead per kilogram of soil from the source of lead chloride) and two types of chelating agents, Ammonium Molybdate (concentration of Mo 10 mg per kg of soil) (AM) and Ethylene diamine tetra-acetic acid (one gram per kilogram of soil) (E) and control. Some of the physical and chemical properties of the soil were measured. In order to contaminated samples of soil, the required value of lead, Ethylene diamine tetra-acetic acid and ammonium molybdate were added to the soils by spray method. After preparing the soil samples, the seed of corn plant (Zea mays L.) was cultivated in soils contaminated by experimental treatments. After harvesting, plant samples transfer to the laboratory, was dried, weighed and milled. Plant samples were digested by dry digestion and were measured the amount of lead in the shoots and roots. Soil samples were transferred to the laboratory for next analysis. Parameters was measured such as dry weight of shoot and root, the concentration of lead in shoot and root, absorption of Pb in shoot and root and availability of Pb in soil by DTPA method. Analysis was performed by using SAS statistical software and figures were drawn in Microsoft Excel. Results and discussion The highest available lead content in soil (extracted by DTPA) is related to Ethylene diamine tetra-acetic acid treatment which it was higher than 29.5% compare to control. The results showed that different levels of lead and form chelates have significant effect (p< 0.01) on dry weight of root and shoot, relative concentration of lead in root and shoot and total absorption of lead in root and shoot. Ammonium molybdate was significantly increased dry weight of root and shoot. According to the results of the highest dry weight of root and shoot of corn plant is related to the level of unleaded (Pb0), the chelate of ammonium molybdate. The highest relative concentration and total absorption of lead in root and shoot was obtained Ethylene diamine tetra-acetic acid-treated at 450 mg per kg of lead (Pb3). Ammonium molybdate compared with Ethylene diamine tetra-acetic acid had a less ability to absorption of lead. Conclusion Obtained results of the comparison amounts of lead of roots and shoots of plants under the effect of use of ammonium molybdate and Ethylene diamine tetra-acetic acid, showed that Ethylene diamine tetra-acetic acid was more effective in increasing concentrations of the element in the corn plant.