Effect of plant density on phytoremediation of polycyclic aromatic hydrocarbons contaminated sediments with Vallisneria spiralis

• Published in: Ecological engineering 2014-12, Vol.73, p.380-385
• Main Authors: Liu, Hongyan, Meng, Fanbo, Tong, Yindong, Chi, Jie
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied ecology; Bacteria; Biodegradation of pollutants; Biological and medical sciences; Biotechnology; Conservation, protection and management of environment and wildlife; Density; Dissipation; Electrode potentials; Environment and pollution; Environmental degradation: ecosystems survey and restoration; Fundamental and applied biological sciences. Psychology; Industrial applications and implications. Economical aspects; Phenanthrene; Phytoremediation; Plant density; Polycyclic aromatic hydrocarbons; Redox potential; Remediation; Sediments; Vallisneria spiralis
• ISSN: 0925-8574; 1872-6992
• DOI: 10.1016/j.ecoleng.2014.09.084

•Effect of plant density of Vallisneriaspiralis on the remediation of PAHs was studied.•Lower plant density should be a better selection for phytoremediation of PAHs.•Dissipation ratio of PAHs was correlated with PAH-degrading bacterial population.•PAH-degrading bacterial population positively linked with sediment redox potential.•The enhanced dissipation of PAHs was mainly related to oxygen released by roots. A 54-day-long study was conducted to investigate the effect of plant density (260, 780, 1300 and 2080plantsm−2) of Vallisneria spiralis on the remediation of sediments contaminated by polycyclic aromatic hydrocarbons (PAHs). Dissipation ratios of phenanthrene and pyrene in sediments were initially the highest in treatment of 2080plantsm−2. However, after a 54-day incubation, no statistical difference was observed in the dissipation ratios under different planting density treatments (p>0.05) except lower dissipation ratio of phenanthrene in treatment of 780plantsm−2. Compared with the unplanted sediments, the dissipation ratios of phenanthrene and pyrene in planted sediments increased by 15.2–21.5% and 9.1–12.7%. Considering the sustainability of the ecosystem, lower plant density (e.g., 260plantsm−2) should be a better selection for phytoremediation of PAHs. Mass balance calculation indicated that plant accumulation accounted for less than 0.39% of the dissipation increment. Furthermore, dissipation ratio of PAHs was positively related to PAH-degrading bacterial population, suggesting that microbial degradation played a major role in the V. spiralis-promoted remediation. The redox potential, a signal of oxygen in sediments, was measured. Positive redox potentials were found in sediments with V. spiralis as a result of oxygen released by roots. Moreover, sediment redox potential positively correlated with PAH-degrading bacterial population. Considering high oxygen demand of PAHs catabolism and reduced conditions in unplanted sediments, it can be concluded that the enhanced dissipation of PAHs is mainly related to oxygen released by roots.