Breakdown of low-level total petroleum hydrocarbons (TPH) in contaminated soil using grasses and willows

ABSTRACT

A phytoremediation study targeting low-level total petroleum hydrocarbons (TPH) was conducted using cool- and warm-season grasses and willows (Salix species) grown in pots filled with contaminated sandy soil from the New Haven Rail Yard, CT. Efficiencies of the TPH degradation were assessed in a 90-day experiment using 20–8.7–16.6 N-P-K water-soluble fertilizer and fertilizer with molasses amendments to enhance phytoremediation. Plant biomass, TPH concentrations, and indigenous microbes quantified with colony-forming units (CFU), were assessed at the end of the study. Switchgrass grown with soil amendments produced the highest aboveground biomass. Bacterial CFU's were in orders of magnitude significantly higher in willows with soil amendments compared to vegetated treatments with no amendments. The greatest reduction in TPH occurred in all vegetated treatments with fertilizer (66–75%) and fertilizer/molasses (65–74%), followed sequentially by vegetated treatments without amendments, unvegetated treatments with amendments, and unvegetated treatments with no amendment. Phytoremediation of low-level TPH contamination was most efficient where fertilization was in combination with plant species. The same level of remediation was achievable through the addition of grasses and/or willow combinations without amendment, or by fertilization of sandy soil.

KEYWORDS:

• phytoremediation
• rhizodegradation
• organic contaminants
• Festuca
• Lolium
• Panicum
• Salix

Acknowledgments

This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 2011-38420-20066 and Hatch project under #CONS000886. Authors thank Gary Levine, Department of Informational Material Sciences at the University of Connecticut, for his assistance with the GC analyses during the research project. We also thank Calvin Warner from the Metro Transportation Authority and members from the Department of Energy and Environmental Protection in their assistance with the contaminated media.