The petroleum refinery sludge is an important source of environmental pollution. Burning and burying of the sludge may cause adverse effects on environment and human health. Thus, other mechanisms for decreasing the toxic effects of hydrocarbon substances in the sludge must be suggested. Therefore, application of new technology such as phytoremediation can be suggested as an environmental friendly method for degradation and remediation of petroleum contaminated soils. In this study, Isfahan refinery complex sludge was dewatered and air dried, then mixed by 0, 10, 20, 30 and 40% w/w ratio with two soils (Typic Haplocalcids and Luvic Calcisols). Different mixtures of soil and sludge land farmed for 21 days and irrigated daily to field capacity. Germination rate and the amount of contaminant uptake were measured. For the germination study seven plants including sunflower ( Helianthus Annuus ), safflower ( Carthamus Tinctorius ), colza ( Brassica Napus ), clover ( Trifollium Repens ), tallfescue ( Festuca Arundianacea ), agropyron ( Agropyron Smithii ) and poxinelia ( Puccenelia Distance ), and in the phytoremediation experiment tallfescue, agropyron and two verities of bermudagrass were used. Microbial respiration, germination percent, yield and the decrease in percent of total petroleum hydrocarbons of Tall fescue and Agropyron risosphers were determined. The lowest germination rate was observed for tallfescue, poxinelia, clover and colza, and the highest was in sunflower and safflower. Sunflower was the only plant that had a 100% germination rate in all the sludge treatments. During the growth period after the germination only tallfescue, agropyron and poxinelia showed resistant to all the sludge levels. In general, bermudagrass yield increased but tallfescue and agropyron yield decreases in sludge contaminated treatments. The root/shoot ratio of tallfescue and agropyron was more than bermudagrass. The tallfescue and agropyron risosphers were more effective in degradation of petroleum hydrocarbons in soil as compared to bermudagrass. In the 40 % sludge treatment tallfescue decreased the total petroleum hydrocarbons content by 65 percent and the highest degradation for agropyron was in the 30 % sludge treatment which was about 55% reduction in total petroleum hydrocarbons. Our study shows that only the germination performance of a plant is not a good indicator of their later growth in the petroleum hydrocarbons contaminated soils. Also in general, our results indicated that tallfescue is the most effective plant for phytoremediation of petroleum hydrocarbons in these soils.
