Effect of Zinc Sulfate and Salicylic Acid on Biological Degradation of Phenanthrene in the Cd Polluted Soil under Sorghum Cultivation Inoculated with Pseudomonas Putida

Abstract

Co-contamination of soils with heavy metals or petroleum hydrocarbons is one of the important environmental problems. This study was done to evaluate the effect of ZnSO₄ and salicylic acid (SA) on biological degradation of phenanthrene in the Cd polluted soil under sorghum cultivation inoculated with Pseudomonas putida (P.putida). Treatments were consisted of applying ZnSO₄ (‌0 and 40 kg/ha), SA foliar application (0 and 1.5 mmol/lit), Cd polluted soil (0, 5 and 10 mg Cd/kg soil) and soil pollution with phenanthrene at the rates of 0, 3 and 6% (W/W) in three replicate in the presence of P. putida. Plant in this experiment was sorghum. At the end of this experiment, plant was harvested and the plant Cd concentration was measured using atomic absorption spectroscopy. On the other hand, the degradation of phenanthrene (%) in the soil and soil microbial respiration via evaluated CO₂ were measured.   Based on the results of this study, applying 40 kg/ha ZnSO₄ significantly decreased the plant Cd concentration by 14.3 %. In addition, a significant increasing by 15.4 % in degradation of phenanthrene in soil was also observed when the soil received 40 kg/ha. The similar results were also observed for SA foliar application.Soil application of ZnSO₄, the presence of P. putida and foliar application of salicylic acid can increase plant resistance to abiotic stresses and thereby have significant effect on biological degradation of phenanthrene. However, the role of plant type on degradation of phenanthrene cannot be ignored.