Phytoremediation of Polycyclic Aromatic Hydrocarbons in Soil: Part I. Dissipation of Target Contaminants

Abstract

Phytoremediation has been demonstrated to be a viable cleanup alternative for soils contaminated with petroleum products. This study evaluated the application of phytoremediation to soil from a manufactured gas plant (MGP) site with high concentrations of recalcitrant, polycyclic aromatic hydrocarbons (PAHs). Two greenhouse studies investigated the potential dissipation and plant translocation of PAHs by fescue (Festuca arundinacea) and switchgrass (Panicum virgatum) in the first experiment and zucchini (Curcubita pepo Raven) in the second. The MGP soil was highly hydrophobic and initially inhibited plant growth. Two unplanted controls were established with and without fertilization. In the first experiment, concentrations of PAHs decreased significantly in all treatments after 12 mo. Plant biomass and microbial numbers were statistically equivalent among plant species. PAH concentrations in plant biomass were negligible for fescue and switchgrass. In the second experiment, zucchini enhanced the dissipation of several PAHs after 90 d of treatment when compared to the unvegetated soil. Plant tissue concentrations of PAHs were not elevated in the zucchini roots and shoots, and PAHs were not detectable in the fruit.

KEY WORDS:

• phytoremediation
• plants
• microorganisms
• biodegradation
• polycyclic aromatic hydrocarbons (PAHs)
• bioremediation
• soil
• rhizosphere

ACKNOWLEDGEMENTS

This project was supported by the US Environmental Protection Agency through the Midwest Hazardous Substance Center headquartered at Purdue University, Lafayette, IN. The authors also appreciate the technical support for contaminant analysis provided by Dr. Jason White from the Connecticut Agricultural Experimental Station.

Notes

^†Organic matter by dry combustion; pH in 2:1 aqueous suspension; electrolytic conductivity by saturated paste; exchange properties by ammonium acetate extraction (NH₄-N by KCl extraction); NO₃, SO₄, boron by water extraction; P by NaHCO₃ extract; Zn, Mn, Cu, and Fe by DTPA extraction; bulk density by clod method; soil texture by hydrometer; and total PAHs by dichloromethane extraction.

^†Concentrations of a given compound at initial and final sampling followed by a different letter are significantly different.

^†Concentrations followed by standard deviation in parentheses.