Abstract
One obstacle to acceptance of natural attenuation by regulators and by the public is an effective and efficient method to monitor its progress. Analysis of the stable isotope ratio in the residual content of three hydrocarbons biodegraded under aerobic laboratory condition indicated enrichment in (super 13) C. A correlation between the residual hydrocarbon concentration and the stable isotope ratio was generated experimentally. Four field sites were analyzed to determine if the same phenomenon occurred. At one field site (origin of the laboratory consortium), the change in isotope ratios for benzene and toluene correlated very well with the degree of degradation predicted from the model. The other sites also showed enrichment in (super 13) C for residual hydrocarbons using both vapor and soil samples.