The Effect of Montmorillonite Nano-Clay on the Changes in Petroleum Hydrocarbon Degradation and Cd Concentration in Plants Grown in Cd-Polluted Soil

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 (۰ and ۱% W/W) in a Cd-polluted soil (۰, ۵, ۱۰ mg Cd/kg soil) and crude oil-polluted soil (۰, ۱ and ۲% W/W). The plant used in this study was Tall Fescue (Festuca arundinacea L.). After ۲۰ 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 ۱% (w/w) montmorillonite nano-clay in Cd-polluted soil (۱۰ mg Cd) without crude oil decreased Cd concentration in plant and increased microbial respiration by ۱۸% and ۳۴%, respectively. In addition, the application of ۱% montmorillonite nano-clay in soil polluted with ۱% crude oil and ۱۰ mg Cd enhanced TPHs degradation by ۲۷%. 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.