2002 Field-Scale Assessments of the Phytoremediation of Weathered Hydrocarbons in Soil

Phytotechnologies involve the plant–assisted bioremediation of organic and inorganic contaminants and are essentially a form of ecological engineering that depends on natural, synergistic relationships among plants, microorganisms and the environment. However, the various plant-associated remediation pathways—and the interactions between these pathways and the biochemical and ecological interactions between plants, microbes, and the environment—give rise to a high level of complexity surrounding phytoremediation. Likewise, the presence of mixed contaminants in the soil adds an even greater level of complexity to the development of practical phytoremediation strategies. Understanding this complexity is crucial to the success of any phytoremediation effort.

Since 1998, our research has focused on assessing the effectiveness of phytotechnologies as a means of reducing petroleum hydrocarbon (BTEX, TPH & PAH) concentrations in soils contaminated with weathered oil product. This focus reflects the fact that (i) many types of PHCs are amenable to microbial degradation; (ii) the phytoremediation of organic contaminants often involves enhanced microbial degradation in the rhizosphere; and (iii) there are an estimated 200,000 PHC-contaminated sites in the Prairie provinces alone. During the past three years, the Phytoremediation team at the University of Saskatchewan has formed effective collaborations with numerous scientists, regulators, and project managers in both government and industry which has culminated in the successful establishment of a strong, interdisciplinary research effort on phytoremediation based in the Department of Soil Science.

The Environmental Biotechnology Applications Division (EBAD) of Environment Canada has been working, since 1997, in partnership with other federal departments, provincial governments, universities and the private sector to assess the utility of plants in a remediation capacity under prevailing Canadian environmental conditions and associated regulatory oversight. The results of this work indicate that to fully exploit and use phytoremediation we need to gain a better understanding of: (i) the pool of phytoremediation species found in Canada; (ii) how phytoremediation operates under unique Canadian climatic conditions; (iii) the mechanisms employed by phytoremediator plants to restore contaminated sites; and (iv) the agronomic requirements needed to maximize phytoremediation as an efficient and cost-effective cleanup technology. So, while there is clear recognition that phytotechnologies have the potential to play an important role in future remediation strategies in Canada, there remains a critical need for ‘field performance data’ to verify this potential, as well as to assess its limitations and determine appropriate uses of the newly emerging phytotechnologies. To address this need, we have been working with our industry and government collaborators to establish two new field sites for inclusion in the USEPA Remediation Technologies Development Forum (RTDF) ‘Phytoremediation Action Team–TPH Subgroup Cooperative Field Trials’ program. The purpose of the program is to “bring together technological, environmental, and regulatory interests to develop and demonstrate phytoremediation technologies that can clean up soils and ground water contaminated with organics, and to achieve regulatory and public acceptance of these technologies”. The site is especially unique in that it involves a flare pit soil in a modified land- farming operation.

The long-term objective of this study is to establish field research sites in Saskatchewan and Alberta to assess and demonstrate the utility of phytoremediation as a means of reducing petroleum hydrocarbon levels in oil-contaminated soils to environmentally acceptable endpoints.