Stimulating the Rate of Phytoremediation of Chromolaena odorata in Crude Oil Contaminated Soil Using Inorganic Urea

Investigation on the use of urea in stimulating the phytoremediation of Chromolaena odorata in a crude oil contaminated soil was carried out at a crude oil spilled site at Botem-Tai, Ogoni, Nigeria. Three phytoremediation treatments labeled A – C in addition to the control (D) were used. The treatments were: A (Chromolaena odorata only), B (Chromolaena odorata + 20 g/m2 urea), C (Chromolaena odorata + 40 g/m2 urea), D (polluted soil without phytoremediation) arranged using Latin Square Design (LSD). Total petroleum hydrocarbon (TPH) and Total hydrocarbon content (THC) in soil and plant samples from the different treatment plots in addition to other soil nutrients were analyzed. The percentage reduction in TPH and THC in soil were as follows: Treatment B, {TPH (92.08%) and THC (95.37%)} > treatment A {TPH (88.95%) and THC (93.37%)}> C {TPH (78.78%) and THC (83.29%)} > Control {TPH (14.76%) and THC (32.90%)}. Treatment C had the highest TPH (2.67 mg/kg) and THC (20.57 mg/kg) accumulation in test plant. Combining stimulant (urea) with phytoremediation also improved soil properties such as pH, Nitrogen and Potassium. With the highest reduction of TPH and THC in treatment B (phytoremediation with 20 g/m2 urea) than other treatments is an indication that low concentration of urea has a stimulatory effect on phytoremediation of crude oil by Chromolaena odorata.