A Fuzzy Logic Model to Determine Petroleum Hydrocarbons Concentration at Different Depths of Contaminated Soil During Phytoremediation

Phytoremediation is a cost-effective, efficient and environment-friendly biological method to reduce petroleumbased contamination in soil. However, limited access to soil samples from various depths during phytoremediation along with the cost, time and effort required for quantitative measurement of total petroleum hydrocarbons (TPH) necessitates the development of a mathematical model to overcome the existing obstacles. Since fuzzy logic is an appropriate method for meddling systems with inadequate or vague and non-specific information, the present study sought to determine TPH concentrations during phytoremediation through such a technique. Based on previous research and the conditions of areas adjacent to Isfahan Oil Refinery (Isfahan, Iran), sorghum and barley were planted in 130 cm long polyvinyl chloride pipes containing contaminated soil samples from the mentioned area. After 17 weeks, TPH concentrations were measured at 25, 50, 75, and 100 cm depths of soil. The percent reduction in TPH concentrations was 23%-35% higher in the presence of sorghum and barley than in unplanted treatments. Fuzzy inference with two inputs (time and depth) and 10 membership functions was used to quantify TPH concentrations (the output) at different depths of planted and unplanted soils during the phytoremediation process. Since the calculated and measured values were consistent, the developed model can be applied in future phytoremediation studies in other contaminated areas.