Effect of EDTA Chelate, Cow Manure, Elemental Sulfur Application and Thiobacillus Inoculant on Cd, Zn and Fe Phytoremediation Efficiency in a Cd-Polluted Soil

Background and Purpose: The Phytoremediation efficiency of heavy metals is one of the important points in environmental studies. This research was conducted to investigate the effect of cow manure, elemental sulfur, and EDTA on Cd uptake by Indian mustard in a Cd-polluted soil in the presence of Thiobacillus thiooxidans. Materials and Methods: Treatments consisted of applying cow manure (0, 5, and 10 g/kg soil), soil application of elemental sulfur (2 g/kg soil), and Cd-polluted soil (0 and 20 mg Cd/kg soil) with 1.5 mmol EDTA/kg soil in the presence of Thiobacillus spp. After 90 days, the Indian mustard plant was harvested and plant Zn, Fe, and Cd concentrations were measured using atomic absorption spectroscopy. In addition, soil microbial respiration was measured. Results: The use of 2 g/kg soil of elemental sulfur significantly increased the plant Cd concentration in the presence and absence of Thiobacillus by 14.2 and 11.7%, respectively. Adding cow manure to the soil at the rates of 5 and 10 g/kg soil significantly increased the plant Cd concentration by 15.7 and 18.1%, respectively. Also, the application of EDTA chelate at the rate 0f 1.5 mmol/kg soil significantly increased the Cd concentration of the plants grown in the Cd-polluted soil (20 mg Cd/kg soil) by 13.6%. Conclusion: The results of the present study showed that using elemental sulfur in the Cd-polluted soil can increase the Cd concentration of the plant which was cultivated in the soil amended with cow manure in the presence of Thiobacillus bacteria. However, the role of soil physic-chemical properties on phytoremediation efficiency cannot be ignored.