biochemical and physical characterization of petroleum hydrocarbon contaminated soils in tehran

contamination of soil was investigated in this study from the tehran oil refining co. of iran. fifteen soil samples were collected at several points in the azimabad, 15 km south of tehran city, iran. samples were collected at depths of 0–30 cm. control sampleswere prepared to determinebackgroundlevels ofsoil contaminationwithpetroleumhydrocarbonsfor comparison with contaminatedsites. total petroleum hydrocarbon (tph) and poly-aromatic hydrocarbons (pah) concentrations varied from 101334.0–101367.1 and 25321.1–25876.6 mg kg -1 respectively. the results elevated levels of tph and pah contents when compared with the control sample. soil acidity (low ph of 5.3–5.9) and low electrical conductivity provided evidence of reduced metabolic activities on the affected site.microbialgrowthrates for bacteria and fungi expressed as colony forming units were 2.62×10 9 and 4.14×10 6 cfu/g soil, respectively for the contaminated and 5.76×10 9 and 6.83×10 6 cfu/g soil, for the control treatments respectively. these drastic changes can have impact on the nutrient cycle and prevents the absorption of nutrients by plant root sand lead to a reduction in yield.