Remediation of Polycyclic Aromatic Hydrocarbon Compounds in Groundwater Using Poplar Trees

• Published in: Environmental science & technology 2005-03, Vol.39 (6), p.1598-1605
• Main Authors: Widdowson, Mark A, Shearer, Sandra, Andersen, Rikke G, Novak, John T
• Format: Article
• Language: English
• Subjects: Applied sciences; Biodegradation, Environmental; Biological and medical sciences; Bioremediation; Biotechnology; Decontamination. Miscellaneous; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environment and pollution; Exact sciences and technology; Freshwater; Fundamental and applied biological sciences. Psychology; Groundwater; Groundwaters; Industrial applications and implications. Economical aspects; Miscellaneous; Natural water pollution; Pollution; Pollution, environment geology; Polycyclic aromatic hydrocarbons; Polycyclic Aromatic Hydrocarbons - chemistry; Polycyclic Aromatic Hydrocarbons - isolation & purification; Polycyclic Aromatic Hydrocarbons - metabolism; Populus; Populus - chemistry; Soil and sediments pollution; Soil Pollutants - isolation & purification; Soil Pollutants - metabolism; Solubility; Trees; Water Pollutants - isolation & purification; Water Pollutants - metabolism; Water treatment and pollution
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es0491681

A seven-year study was conducted to assess the effectiveness of hybrid poplar trees to remediate polycyclic aromatic hydrocarbon (PAH) compounds in soil and groundwater at a creosote-contaminated site. A reduction in the areal extent of the PAH plume was observed in the upper half of the 2-m-thick saturated zone, and PAH concentration levels in the groundwater declined throughout the plume. PAH concentrations began to decline during the period between the third and fourth growing seasons, which coincided with the propagation of the tree roots to the water table region. Remediation was limited to naphthalene and several three-ring PAHs (acenaphthylene and acenaphthene). PAH concentrations in soil and aquifer sediment samples also declined over time; however, levels of four-ring PAHs persisted at the lower depths during the study period. The naphthalene to total PAH concentration ratio in the most contaminated groundwater decreased from >0.90 at the beginning of the second growing season to approximately 0.70 at the end the study. Remediation in the lower region of the saturated zone was limited by the presence of a 0.3-m-thick layer of creosote present as a dense nonaqueous phase liquid (DNAPL). The nearly steady-state condition of the PAH concentrations observed during the last three years of the study suggests that the effectiveness of the phytoremediation system is limited by the rate of PAH dissolution from the DNAPL source.