An Investigation of the Ability of a ¹⁴C-Labeled Hydrocarbon Mineralization Test to Predict Bioremediation of Soils Contaminated with Petroleum Hydrocarbons

ABSTRACT

Bioremediation is a widely accepted technology for the remediation of hydrocarbon-contaminated soil. Treatability studies are usually carried out to assess the biodegradation potential of the contaminants and to design optimal treatments. Laboratory studies measuring soil respiration are often used. One method consists of monitoring the mineralization of a ¹⁴C-labeled hydrocarbon surrogate added to the contaminated soil. This study investigates the ability of this method to properly predict the removal of the hydrocarbon contaminants initially found in soils. Mineralization of ¹⁴C-labeled hexadecane was monitored in seven soils contaminated with various hydrocarbon mixtures, both fresh and weathered, in microcosm experiments. Reduction of total petroleum hydrocarbon (TPH) concentrations was measured simultaneously in separate microcosms. Both types of microcosms were subjected to the same amendment regimes. For all soils, poor correlation was observed between the mineralization and TPH reduction data sets. Mineralization data supported contaminants removal data in only one soil. Findings indicate that the radioactive surrogate method does not reliably predict the extent of, and the effect of amendments on, the removal of the hydrocarbons initially present in soil, and may therefore predict suboptimal treatment regimes. Recommendations for soil treatability protocols are provided.

KEYWORDS:

• ¹⁴C-labeled hexadecane
• bioremediation
• microcosms
• mineralization
• petroleum hydrocarbons
• radioactive surrogate
• soil respiration
• treatability study

ACKNOWLEDGEMENTS

This work was financially supported by the Natural Sciences and Engineering Research Council of Canada, the Department of National Defence and Parks Canada. We thank Dr. W. Mohn, University of British Columbia, for providing the hydrocarbon-degrading microbial culture used in this study. We also thank M. Serran, E. Creber, M. C. Tremblay, J. Peel, G. Decarie, and M. Dagenais for their valuable help in conducting the laboratory work and providing insight, ideas, and comments.

Notes

^a Clean CFB Kingston soil was contaminated in the laboratory with diesel fuel or motor oil.

^a Within each soil type and measurement, values with different letters indicate significant difference (α = .05) between treatments.

^b Nonzero values indicate a significant change in TPH (α = .05). Negative values indicate an increase.