CONCLUSIONS
The results of this study demonstrate that in lab reactors containing soil, the target compounds 2H-tetradecane and phenyldodecane are biologically degraded, converted into their corresponding fatty acids and incorporated into higher lipids. The labels in both target compounds survived the metabolic process and gave identifiable daughter compounds traceable directly to the parent molecules. To our knowledge this is the first demonstration of the formation of metabolic products of stable isotope and phenyl labeled alkanes during biological degradation in soils.

The findings show that both phenyl and deuterium labeled alkanes can be used as sensitive tools for the confirmation of biodegradation. The rates of degradation of 2H-tetradecane and phenyldodecane are similar to that of diesel fuel and their unlabelled analogues. We predict that longer or shorter chain length labeled compounds offer the opportunity for easy manipulation of the rate of degradation to suit needs in the field. Further, the metabolic products are easy to detect in soil because they appear against a blank background, unlike native metabolites. Under optimal conditions of temperature and nutrients, the metabolites can be seen within a few days. The results also indicate that the metabolites are themselves further degraded. This is an important prerequisite for the use of these labeled compounds as markers for biodegradation at contaminated sites.

Potential application of these markers include assessment of biodegradation potential of soils in lab scale experiments or under actual field conditions and for verification of biodegradation during the bioremediation of contaminated sites. We are currently investigating these applications.

ACKNOWLEDGEMENT
The project was funded jointly by National Science and Engineering Research Council of Canada, Bell Canada and Investigative Science Incorporated.

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