Fate of petrogenic hydrocarbons during phytoremediation of petroleum impacted soils

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Large amounts of contaminants, including petroleum hydrocarbons (PHC), have been released into the environment. Their persistence in soils at > 30,000 known sites in Canada necessitates the development of cost effective and efficient remediation technologies. We have developed a plant growth promoting rhizobacteria (PGPR) enhanced phytoremediation system (PEPS) that is effective at degrading PHC in soils. PEPS has been successfully used in several full scale field trials in ON, AB, MB and QC. Although we have shown that PHC can be degraded in soils using this system, accumulation of phytogenic hydrophobic material due to plant growth can confound the results of standard Canadian Council of Ministers of the Environment (CCME) analyses required by regulations. In part, this is because many root-derived compounds are natural analogs of PHC constituents. Accepted analytical protocols supported by CCME do not distinguish between petrogenic and phytogenic compounds. Techniques such as gas chromatography/mass spectrometry (GC/MS) analyses can distinguish petrogenic materials from other organic compounds. These methods have been used for chemical fingerprinting to assess liability after accidental PHC releases, but have not been applied to phytoremediation. Application of GC/MS techniques and risk assessment can provide the basis for calibrating data obtained via the CCME PHC analyses, and will provide the needed methodologies for distinguishing PHC from phytogenic materials in soil samples. The overall goal of the proposed research is to characterize and quantify the hydrophobic compounds in soil during the course of phytoremediation to distinguish petrogenic material from phytogenic material to better meet regulatory standards. This will be done by comparing the extractable hydrophobic material and soil toxicity of planted impacted areas to planted unimpacted control areas. Monitoring the temporal appearance of phytogenic compounds that accumulate during phytoremediation, and accounting for their presence in standard CCME PHC analyses, would enhance the reliability of this environmentally responsible remedial strategy and facilitate its use at a broader range of impacted sites.