Remediation of Polycyclic Aromatic Hydrocarbon Compounds in Groundwater Using Poplar Trees

Abstract

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 bythe 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.

High aromatic ring-cleavage diversity in birch rhizosphere: PAH treatment-specific changes of I.E.3 group extradiol dioxygenases and 16S rRNA bacterial communities in soil

“…Generally, the rhizosphere of plants harbours a higher diversity of bacteria than the surrounding bulk soil due to root exudates and oxygen that stimulate bacteria (Briones et al, 2003). Most interest in phytoremediation with woody plants has been devoted to Populus (Spriggs et al, 2005;Widdowson et al, 2005;Zalesny et al, 2005) and Salix (Vervaeke et al, 2003) with the aim to combat heavy metal pollution. Not much attention has been devoted to elucidate applicability of woody plants for remediation of organic pollution (Tesar et al, 2002;Mueller and Shann, 2006;Palmroth et al, 2006).…”

Novel Intermediates of Acenaphthylene Degradation by Rhizobium sp. Strain CU-A1: Evidence for Naphthalene-1,8-Dicarboxylic Acid Metabolism

“…Due to their carcinogenicity, mutagenicity, and toxicity, PAHs are listed as priority toxic pollutants by the United States Environmental Protection Agency (10). Acenaphthylene, one of the listed PAHs, is found as a constituent of coal tar and tobacco smoke (15) and of organic contaminants in groundwater (31). This compound is well-known for causing adverse effects in humans as well as aquatic organisms (14).…”

Volatilization and Biodegradation of Naphthalene in the Vadose Zone Impacted by Phytoremediation

“…Naphthalene is the primary contaminant volatilized into pore air and dissolved into groundwater from the creosote, which is present as a dense nonaqueous phase liquid (DNAPL) in the surficial aquifer. Previous studies at the site demonstrated that naphthalene undergoes preferential remediation over the PAHs with three or more rings and enhanced biodegradation is occurring in areas impacted by poplar trees (1,2). Direct volatilization of naphthalene to the atmosphere was measured at the site and found to be enhanced by the presence of the phytoremediation system because the trees reduce the saturated thickness separating the submerged DNAPL and the water table and thus enhance vertical fluxes of contaminants (3).…”

“…Phytoremediation of polycyclic aromatic hydrocarbon (PAHs) compounds using poplar trees has been studied for a period of 7 years at a creosote-contaminated site in north-central Tennessee (1). Naphthalene is the primary contaminant volatilized into pore air and dissolved into groundwater from the creosote, which is present as a dense nonaqueous phase liquid (DNAPL) in the surficial aquifer.…”