Contamination with heavy metals and petroleum hydrocarbons is considered as an environmental problem. Thus, this research was done to evaluate the effect of montmorillonite nano-clay on the changes in petroleum hydrocarbon degradation and cadmium (Cd) concentration in plant grown in a Cd-polluted soil. Treatments consisted of two levels of montmorillonite nano-clay (0 and 1% W/W) in a Cd-polluted soil (0, 5, 10 mg Cd/kg soil) and crude oil-polluted soil (0, 1 and 2% W/W). The plant used in this study was Tall Fescue (Festuca arundinacea L.). After 20 weeks, the concentration of Cd in plants was measured by atomic absorption spectroscopy and the total petroleum hydrocarbon (TPHs) in the soil was determined using the GC-mass spectrometry. Soil respiration was determined according to the method used by Qiao et al. ANOVA was used for statistical analysis of data. The least significant difference (LSD) test was used to determine the differences between the means. The application of 1% (w/w) montmorillonite nano-clay in Cd-polluted soil (10 mg Cd) without crude oil decreased Cd concentration in plant and increased microbial respiration by 18% and 34%, respectively. In addition, the application of 1% montmorillonite nano-clay in soil polluted with 1% crude oil and 10 mg Cd enhanced TPHs degradation by 27%. The use of montmorillonite nano-clay increased Cd adsorption in soil which resulted in an increase in microbial respiration and, hence the degradability of petroleum hydrocarbon in the soil.

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Background: Chemical stabilization of heavy metals in acidic soil is one of the important points in environmental pollution. Thus, this research was conducted to investigate the effect of organic and inorganic amendments on lead (Pb) immobilization in the Pb-polluted soil. Methods: Treatments were consisted of applying cow manure (0, 15, and 30 t/ha), and applying cow bone and phosphate rock (5% (W/W)) in the Pb (0, 800, and 1600 mg Pb/kg soil)-polluted soil. The plant used in this experiment was canola. After 70 days, the plants were harvested and soil and plant Pb concentration was measured using atomic absorption spectroscopy (AAS). Results: Applying 15 and 30 t/ha of cow manure in the Pb (1600 mg Pb/kg soil)-polluted soil significantly decreased the soil Pb concentration by 14.3 and 17.2%, respectively. For plant Pb concentration, it was increased by 11.8 and 15.1%, respectively. A significant decrease in plant Pb concentration was measured, when the soil under cultivation of the plant was amended with 5% (W/W) phosphate rock powder. For the plants grown on the soil, which was amended with 5% (W/W), the plant Pb concentration decreased by 17.6%. In addition, applying organic and inorganic amendment significantly decreased the bio-concentration factor (BCF), while the soil microbial respiration increased. Conclusion: The results of this study showed that applying 15 and 30 t/ha cow manure or calcium and phosphorus sources such as cow bone and phosphate rock powder (5% (W/W) can decrease the soil Pb availability and prevent the Pb translocation from soil to plants.