Effects of plant density on the bioremediation of soils contaminated with polyaromatic hydrocarbons

This study aims to evaluate the effects of plant density on the degradation of polyaromatic hydrocarbon (PAH) compounds in soils contaminated with crude oil. In this work, Axonopus compressus was applied as a bioremediator given its extensive and successful use in phytoremediation. A. compressus was planted at the density of three (pot-3), five (pot-5) or seven (pot-7) plants in pots containing soil contaminated with crude oil at the concentration of 20 g kg−1. Two pots were designated as controls: one containing unplanted soil contaminated with crude oil (pot-C) and one containing uncontaminated soil as control (pot-0). All planted and unplanted pots were irrigated with nutrient solution as needed. This study was performed for 2 months. The degradation of PAH compounds in soil was evaluated through ultraviolet fluorescence technique. Results showed that PAH degradation was enhanced as plant density increased. Specifically, after 2 months, PAH contents decreased by 69%, 75.8% and 82.3% in pot-3, pot-5 and pot-7, respectively, relative to those in pot-C. High plant densities mitigated the adverse effects of crude oil contamination on plant growth. Thus, this study demonstrated that high plant densities promote the phytoremediation of soil contaminated with hydrocarbon compounds.